TAC42059_V1.1-SG-Ed2.0-PDF_CE

7302-7360 ISAMHigh Cap. NT/5520 AMS - Redundancy configurationsStudent Guide

Copyright © 2013 Alcatel-Lucent. All Rights Reserved.

COPYRIGHT © ALCATEL-LUCENT @@YEAR. ALL RIGHTS RESERVED.

Student GuideTAC42059_V1.1-SG Edition 2.0

Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel-Lucent

@@COURSENAME@@PRODUCT

2COPYRIGHT © ALCATEL-LUCENT 2013. ALL RIGHTS RESERVED.

Terms of use and legal notices

Switch to notes view!TERMS OF USE AND LEGAL NOTICE

Alcatel-Lucent provides this training course to you subject to these Terms of Use and Legal Notice. Your use of this training course and/or this site constitutes your acceptance of and agreement to these Terms of Use and Legal Notice. These Terms of Use and Legal Notice, as well as the contents of this training course, may be updated or amended by Alcatel-Lucent from time to time without prior notice to you. Your use of the Alcatel-Lucent training materials after such update or amendment constitutes your acceptance of and agreement to said updated or amended Terms of Use and Legal Notice.

SAFETY WARNING

Alcatel-Lucent training materials can be for products or refer to products that have both lethal and dangerous voltages present. Always observe all safety precautions and do not work on the equipment alone. The user is strongly advised not to wear conductive jewelry while working on the products. Equipment referred to or used during this course may be electrostatic sensitive. Please observe correct anti-static precautions.

PERMISSION TO USE CONTENT

The information, communications, scripts, photos, text, video, graphics, music, sounds, images and other materials provided in this training course (collectively the "Content"), is intended for the lawful use of employees of Alcatel-Lucent and other authorized participants in this Alcatel-Lucent training course. You are hereby granted a non-exclusive, non-transferable permission to access and use the Content solely for your personal training and non-commercial use. This permission may be terminated by Alcatel-Lucent at any time for any reason or no reason, with or without notice. You must immediately cease use of the Content upon such termination.

COPYRIGHTS AND TRADEMARKS

The unauthorized copying, displaying or other use of any Content from this training course is a violation of the law and Alcatel-Lucent’s corporate policies. The Content is protected in France, the U.S. and other countries by a variety of laws, including but not limited to, copyright laws and treaty provisions, trademark laws, patent laws and other proprietary rights laws (collectively, "IP Rights"). In addition to Alcatel-Lucent’s IP Rights in the Content, in part and in whole, Alcatel-Lucent, and any of the third parties who have licensed and/or contributed to the Content, owns a copyright in the formatting and presentation of the Content.

Alcatel-Lucent does not grant you any permission to use the Content other than the permission expressly stated in these Terms of Use and Legal Notice. All other use of Content from this training course, including, but not limited to, modification, publication, transmission, participation in the transfer or sale of, copying, reproduction, republishing, creation of derivative works from, distribution, performance, display, incorporation into another training course or presentation, or in any other way exploiting any of the Content, in whole or in part, for uses other than those expressly permitted herein is strictly prohibited and shall not be made without Alcatel-Lucent’s prior written consent. All characters appearing in this training course are fictitious. Any resemblance to real persons, living or dead, is purely coincidental.

There may be a number of proprietary logos, marks, trademarks, slogans and product designations found in the


There may be a number of proprietary logos, marks, trademarks, slogans and product designations found in the Content. Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logos are trademarks of Alcatel-Lucent. All other trademarks are the property of their respective owners. Alcatel-Lucent does not grant you a license to use any of the foregoing logos, marks, trademarks, slogans and product designations in any fashion. Granting of the right to access and use the Content for training purposes does not confer upon you any license under any of Alcatel-Lucent’s or any third party's IP Rights.

DISCLAIMER

ALCATEL-LUCENT DISCLAIMS ALL WARRANTIES REGARDING THE TRAINING COURSES OR THE CONTENT, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. THE ALCATEL-LUCENT WILL NOT BE RESPONSIBLE OR LIABLE FOR ANY INJURY, LOSS, CLAIM, DAMAGE, OR ANY SPECIAL, EXEMPLARY, PUNITIVE, INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND (INCLUDING WITHOUT LIMITATION LOSS PROFITS OR LOSS SAVINGS), WHETHER BASED IN CONTRACT, TORT, STRICT LIABILITY OR OTHERWISE, THAT ARISES OUT OF OR IS IN ANY WAY CONNECTED WITH (A) ANY USE OR MISUSE OF THE CONTENT OR THE TRAINING COURSES BY YOU, OR (B) ANY FAILURE OR DELAY BY ALCATEL-LUCENT, ITS OFFICERS, DIRECTORS, AGENTS OR EMPLOYEES IN CONNECTION WITH THE CONTENT OR THE TRAINING COURSES (INCLUDING, WITHOUT LIMITATION, THE USE OF OR INABILITY TO USE ANY COMPONENT OF THE CONTENT OR TRAINING BY YOU). SOME JURISDICTIONS LIMIT OR PROHIBIT SUCH EXCLUSION OF WARRANTIES OR LIMITATION OF LIABILITIES AND SO THE FOREGOING EXCLUSION OF WARRANTIES OR LIMITATION OF LIABILITY MAY NOT APPLY TO YOU.

GOVERNING LAW

These Terms of Use and Legal Notice are governed by the laws of France. The operation and use of the training course is governed by the laws of the country that governs your employment contract, if applicable. If any provision of these Terms of Use and Legal Notice, or the application thereto to a person or circumstance, is held invalid or unenforceable by law, statute or a court of competent jurisdiction, for any reason, then such provision shall be modified and/or superseded by a provision that reflects the intent of the original provision as closely as possible. All other provisions of these Terms of Useand Legal Notice shall remain in full force and effect. You may not assign these Terms of Use or any permission granted hereunder without Alcatel-Lucent’s prior written consent. Nothing herein shall be deemed an employment agreement or an offer of employment or an alteration in any way of a user’s terms of employment with or within Alcatel-Lucent.

Copyright © 2013 Alcatel-Lucent. All Rights Reserved



Course outline

1. Technologies

1. STP RSTP MSTP Tech

2. NE Operation

1. IHUB RSTP LAG NTRedundancy

Welcome to 7302-7360 ISAM

High Cap. NT/5520 AMS - Redundancy configurations

1. Technologies

1. STP RSTP MSTP Tech

2. NE Operation

1. IHUB RSTP LAG NTRedundancy




Course objectives

� Upon completion of this course, you should be able to:

� Describe Rapid Spanning Tree Protocol (STP),� Describe Rapid Spanning Tree Protocol (RSTP),� Describe Mulitiple Spanning Tree Protocol (MSTP),� Describe the most important xSTP parameters,� Describe and configure Link Aggregation (LAG),� Describe and compare the different scenarios for access resiliency (NT redundancy),� Configure NT protection.

7302-7360 ISAM


Upon completion of this course, you should be able to:

� Describe Rapid Spanning Tree Protocol (STP),

� Describe Rapid Spanning Tree Protocol (RSTP),

� Describe Mulitiple Spanning Tree Protocol (MSTP),

� Describe the most important xSTP parameters,

� Describe and configure Link Aggregation (LAG),

� Describe and compare the different scenarios for access resiliency (NT redundancy),

� Configure NT protection.


Your feedback is appreciated!

Please feel free to Email your comments to:

[email protected]

Please include the following training reference in your email:

TAC42059_V1.1-SG Edition 2.0

Thank you!

7302-7360 ISAM � High Cap. NT/5520 AMS - Redundancy configurationsTechnologies � STP RSTP MSTP Tech

1 � 1 � 1COPYRIGHT © ALCATEL-LUCENT 2013. ALL RIGHTS RESERVED.

Module 1STP RSTP MSTP Tech

Section 1Technologies

7302-7360 ISAM


TAC42059_V1.1-SG Edition 2.0

TAC42058_HO01 Edition I2.0

Learning experience powered byAlcatel-Lucent University



Section 1 � Module 1 � Page 1



Blank page

This page is left blank intentionally




Document History

Edition Date Author Remarks

01 2013-01-22 Last name, first name First edition

02 Jan/2014 ALU-University Madrid [R4.5/R4.6 – Ams R9.2.30]



Module objectives

After completing this section, you’ll be able to:

• Describe Spanning Tree Protocol

• Bridge Ids and Root Selection

• BPDU format

• Bridge and Port Definitions

• Port States and Convergence

• Describe Rapid Spanning Tree Protocol

• New BPDU format


• Topology Change Behaviour

• Describe Multiple Spanning Tree Protocol

• Vlan Instances

• Regions






Module objectives [cont.]







Table of Contents

1 Spanning Tree Protocol - Principles 7

2 Rapid Spanning Tree Protocol 20

3 Multiple Spanning Tree Protocol 31

Page

1 Spanning Tree Protocol - Principles 71.1 What is Redundancy and Why? 81.2 Redundancy is needed- How about loops? 91.3 Example of a Loop 101.4 Spanning Tree Protocol 111.5 Root Switch Election 121.6 Bridge ID Format 131.7 BPDU and Bridge ID 141.8 Port Roles 151.9 Spanning Tree Port Stages 161.10 Spanning tree – Example 171.11 Spanning Tree Protocol – Convergence – Topology Change 181.12 STP – Convergence Time 192 Rapid Spanning Tree Protocol 202.1 Rapid Spanning Tree Protocol - States 212.2 (Rapid) Spanning Tree Protocol - BPDU Format 222.3 During Topology Change – BPDU Handling 232.4 Example: Inferior BPDUs – Convergence for Indirect Links 242.5 Rapid Spanning Tree Protocol - Link Designations 252.6 Topology Change Detection and Propagation 262.8 Rapid Spanning Tree Protocol – Sync Process 292.9 Rapid Spanning Tree Protocol – Convergence 303 Multiple Spanning Tree Protocol 313.1 How about Multiple VLAN situation? 323.2 Multiple Spanning Tree Protocol 333.3 What is MSTP - Multiple Spanning Tree Protocol 343.4 Multiple Spanning Tree Protocol - Regions 35






Table of Contents [cont.]







1 Spanning Tree Protocol - Principles







1.1 What is Redundancy and Why?

• 100 percent uptime is perhaps impossible, but many organizations try

to achieve 99.99 percent.

• To achieve such a goal requires extremely reliable networks.

• Redundancy is needed to eliminate network outages caused by point

of failures.

• Failure on forwarding link!

?




Many companies and organizations increasingly rely on computer networks for their

operations. Access to file servers, databases, the Internet, intranets, and extranets is

critical for successful businesses. If the network is down, productivity and customer

satisfaction decline.

If a path or device fails, the redundant path or device can take over the tasks.




1.2 Redundancy is needed- How about loops?

• Broadcast and multicast frames are flooded out all ports, except the

one on which the frame was received. That will result in broadcast

storms. (NO TTL in L2 !)

• SOLUTION! --- To create Logical Loop Free Topologies.

• 802.1D Bridge Protocol

• Interconnection of IEEE 802 LANs

• Includes Spanning Tree Protocol (STP)

LOOP !!!

When a broadcast message received in a bridge, it will be flooded to everybody connected.




When a broadcast message received in a bridge, it will be flooded to everybody connected.

In redundancy networks, this process will result in loops that the switches are not aware of.

Loops consume a lot of CPU, bandwidth and resources in the end.

Multicasts are treated as broadcasts by the switches. Broadcast and multicast frames are

flooded out all ports, except the one on which the frame was received.

802.1D Bridge Protocol

�Interconnection of IEEE 802 LANs

�Includes Spanning Tree Protocol (STP)

802.1W Rapid Bridge Protocol

�Amendment to IEEE Std 802.1D

�Rapid Spanning Tree Protocol (RSTP)

Multiple Spanning Tree Protocol (MSTP)

�Provides STP to run on multiple VLANs.

�Originally defined in IEEE 802.1s and later merged into IEEE 802.1Q -2003




1.3 Example of a Loop

MAC1

12

MAC2

Phys MAC addr. Port nbr

Phys MAC addr. Port nbr

12

M1�� M21

P1 1

P1 1 2

2

M1�� M2

3

P1 2 5

M1�� M26

M1�� M2

LOOP!7

Multiple active paths between hosts cause loops

� end stations receive duplicate messages

� switches learn host MAC addresses on multiple interfaces

This results in an unstable network

M1�� M2

4

PC1PC2

An example of a loop is depicted in the following drawing. A loop can appear in a meshed




An example of a loop is depicted in the following drawing. A loop can appear in a meshed

network topology or where link redundancy is desired. The goal of Link redundancy is if a

particular link fails another one can take over making sure frames are forwarded towards

the network.

In our example two switches connect two network segments. [1]In this case when PC 1 sends

a message to PC 2, both switches receive this message with the source address of PC 1 and

destination address of PC 2, their respective MACs. [2]The source address of PC 1, MAC1 is

learned at both switches in port1. Since both switches don’t know the destination address,

MAC2, they will broadcast the Ethernet frames to all the ports. In this example port 2 of the

switches. [3]So let’s say the upper switch sends first the frame. [4]Not only will PC 2 will

receive the frame but also the lower switch in port 2. [5] The lower switch will think that PC

1 has moved so it overwrites the previous entry in its self learning table and broadcasts this

frame to all its ports, in this case port 1 [6]. This creates a loop which endlessly travels

through the network consuming available bandwidth [7]. To solve this problem STP could be

activated. The STP will make sure there is only one active path out of multiple paths

available between the two end points [8].




1.4 Spanning Tree Protocol

• Ethernet switches can implement the IEEE 802.1d Spanning-Tree Protocol and use algorithm to construct a loop free shortest path network.

• Algorithm based on: Cost, Priority, Mac-Address




Like mentioned before, in switch networks, redundant paths can cause loops

The Spanning Tree Protocol (STP) prevents loops by allowing only one single

path between any pair of hosts. The STP is transparent to hosts

The STP relies on BPDU messages: Bridged Protocol Data Units

and its Key functions are:

�find an active topology without loops

�By blocking and unblocking ports

�and discover failures




BPDU = Bridge Port Data Unit

BID= Bridge ID

How does the STP protocol work?

�In order to calculate a spanning tree, switches exchange information using BPDU messages (Bridged Protocol Data Units) [Animation 1].

�The first step in the calculation of a spanning tree is to select a root switch [Animation 2]. By default, this is the switch with the lowest bridge identifier (BID). The BID is made up of a priority value and a MAC address (one selected from all the MAC addresses it has per port). The operator will give a priority so as to assign the one it wants as the root switch. By default the priority value is set to 32768. The operator has to be very careful about setting the priority value of the switches. In case of equal priorities, the switch with the lowest Mac-Address will be elected as a root switch. This may result in selecting a root switch which may be the lowest in processing and switching. Once all switches have their own BID each switch assumes it’s the root and broadcasts its BPDU by default every 2 seconds, containing its bridge id. The switches soon find out which one is the real root switch.

�Each switch calculates the best path (lowest cost) to the root. The cost is associated with the bandwidth which is assigned by the operator for each port of the switch. The higher the bandwidth the lower the cost [Animation 3]. The resulting paths make up the spanning tree and the corresponding ports on those paths are enabled (ports are in a forwarding state which can handle traffic). Other ports are blocked (standby). No frames (traffic) can pass through blocked switch ports! (No loops are possible!)

�In case an active link fails or a new switch is added, the STP will detect this and set up a new spanning tree. A blocked link will become active.

�RSTP (Rapid Spanning Tree Protocol) has a mechanism to recover from failure situations (or adding a new switch) much quicker than STP: RSTP converges faster than STP.

.




1.6 Bridge ID Format

• Bridge ID is used to identify each switch. The lower BID in the switched

network will be elected as Root Bridge.

• When BIDs are received by all switches, each switch replaces higher

Root-IDs with lower Root-IDs in the BPDUs sent out.

• Network Administrators can set switch priority to elect root bridge.

Bridge

PriorityMAC-Address

2 Bytes

Range: 0 – 65,535

Default: 32768

6 Bytes




By default the priority value set to 32768. The network administrator has to be very careful

about setting the priority value of the bridges in the switching domain. Because, in case of

equal priorities, the switch with the lowest Mac-Address will be elected as a root switch.

That may result in selecting the oldest one as a root switch which may be the least powerful

router.




1.7 BPDU and Bridge ID

• First decision is to select “Root Bridge”

• BPDUs are sent out from each switch with Bridge IDs (BID)

• BID consists of Bridge Priority and Mac-Address of the switch

• By default, BPDUs are sent every two seconds

Root BID

Root Path Cost

Sender BID

Port ID

Who is the Root Bridge ?

How far away is the Root Bridge?

What is the BID of the switch?

What Port did the switch use for sending this BPDU?

BPDU







1.8 Port Roles

• After Root Switch election; port roles are defined

100 M

10 M100 M

1 G

D D

D

R

R

R

If receiving best BPDU on segment

If sending best BPDU on segment

Lowest Priority ��ROOT SWITCH

Alternate port(Blocked)

R

D

Spanning tree works in first instance by selecting a root bridge on the LAN. This particular bridge is




Spanning tree works in first instance by selecting a root bridge on the LAN. This particular bridge is

elected through the exchange of BPDU. The switch that has the lower Bridge-ID becomes the Root

Switch. If the Bridge-IDs are the same for all switches, then the switch with the lower Mac-Address will

be elected as Root Switch.

When the root bridge is selected, then each other bridge selects one of its ports with the least path cost

to the root bridge. The least cost path is determined by STP looking at the bandwidth of the link.

All ports on the root bridge are known as designated ports and are in what is known as forwarding state.

Forwarding state ports can send and receive traffic.

All of the other bridges present are known as non-root bridges. They choose a port known as a root port

which sends and receives traffic.

On non-root bridges only one port can be designated and all others are blocked. Designated ports

forward MAC addresses. Designated ports are selected after the bridge determines the lowest cost path

to get to the root bridge.

By using this method, the redundant links are closed down. They can be opened again if there is a

change in network topology and the link is needed once more.

PORT ROLES

The Root Port and Designated Port remains with the same functionality, but a Blocking Port has two

roles now. Backup Port and Alternate Port. Spanning Tree Algorithm defines ports based on BPDUs.

Within the value inside BPDU messages, the port can be compared with others and the action can be

taken accordingly.

Alternate Port: The interface that we are receiving better BPDU values to access to the Root Bridge.

When the Designated Port fails on the switch then the alternate port will be used for the path.

Propagation delays can occur when protocol information passes through a switched LAN. As




Propagation delays can occur when protocol information passes through a switched LAN. As

a result, topology changes can take place at different times and at different places in a

switched network. When a Layer 2 interface transitions directly from non-participation in

the spanning tree topology to the forwarding state, it can create temporary data loops.

Ports must wait for new topology information to propagate through the switched LAN before

starting to forward frames. They must allow the frame lifetime to expire for frames that

have been forwarded under the old topology.

Switch ports running STP can be in one of four (five) states:

�Blocking – Port will decide whether it is a Root Port , Designated Port or Blocked Port.

During this stage the port listens but will not forward frames, the port is not used by

user traffic.

�Listening and Learning – Switch determines if there are any other paths to Root Switch

or not. The path with the least cost becomes Root Port for Non-root Switches and

Designated Port for the Root Switch. BPDUs are still being processed in both states but

BPDUs can not be read in listening state. The port is still not used but the bridge can

already learn mac-addresses from this port.

�Forwarding - Sends and receives frames on the port, the port is used to carry user

traffic

�(Disabled – virtually non-operational)

RSTP ports can be in only three different states. See further.




1.10 Spanning tree – Example

0

11 10

12 13 9

2 3

6 7 8

5 1

4

19

4

2 2

4 4

419 19

19

100 100 100

root

path cost

Bridge(identifier)

LANPath cost

10Mbps �� 100100Mbps �� 191000Mbps �� 410Gbps �� 2

So here you have it. This is the result of activating the STP in the network. Most likely there are more links than what is shown here but the STP has blocked them in order to avoid loops. Every green circle is a switch




So here you have it. This is the result of activating the STP in the network. Most likely there are more links than what is shown here but the STP has blocked them in order to avoid loops. Every green circle is a switch with its corresponding bridge id [1] and the root switch having the lowest BID [2]. The Path cost corresponds to each link [3] which has a relation with the link bandwidth (lower cost means higher bandwidth [4]). With this loop free topology if switch id 4 wants to send traffic to switch id 6 then it must take the following path via the root switch 5].Let’s sum up on how the Spanning-Tree Protocol eliminates loops in the network:1 The switch with the lowest switch identifier among all switches on all LAN segments is the root switch. The network administrator can assign a lower switch priority to a selected switch to control which switch becomes the root, or the administrator can use default switch priorities and allow the Spanning-Tree Protocol to determine the root.2 Each switch port is associated with a path cost.The path cost represents the cost of transmitting a frame to a switched segment through that port. A network administrator typically configures a cost for each port based on the speed of the link 3 Each switch determines its root port and root path cost.The root port is the port that represents the shortest path from itself to the root switch. The root path cost is the total cost to the root. All ports on the root switch have a zero cost.4 All participating switches elect a designated switch from among the switches on that LAN segment. A designated switch is the switch on each LAN segment that provides the minimum root path cost. Only the designated switch is allowed to forward frames to and from that LAN segment towards the root.5 All participating switches select ports to be included in the spanning tree. The selected ports will be the root port plus the designated ports for the designated switch. Designated ports are those where the designated switch has the best path to reach the root. In cases where two or more switches have the same root path cost, the switch with the lowest switch identifier becomes the designated switch.6 Using the preceding steps, all but one of the switches directly connected to each LAN segment are eliminated, thereby removing all multiple LAN loops.Spanning tree reconfigurationThe root switch is in charge of periodically sending BPDUs on the network. If a given switch does not receive any root BPDU for a max_age timer (usually 20 s), it will request a new root election and will compute its ports state again.All ports then pass in listening state for a forward_delay period (usually 15 s). This is supposed to be the time the switch needs to collect information and take a decision regarding the port state. The port should then go into a blocked or learning state.The learning state will last forward_delay again. This elapse of time is necessary to ensure the new spanning tree configuration has been seen by all switches on the network and avoid any temporary loops. Yet the switch can already learn addresses from this port. Finally the port may change to forwarding state or even blocked if new information has told the switch to block it.If a switch sees a local topology change it will immediately send a topology change notification to the root, which will notify this change to other switches asking them to refresh their address database.




1.11 Spanning Tree Protocol – Convergence – Topology Change

TC BPDU

1st: TC is generated and sent to Root.

2nd: The Root advertises the TCA for max_age +

forward_delay seconds

TCATCA

TC : Topology ChangeTCA: TC Ack




When an 802.1D bridge detects a topology change, it uses a reliable mechanism to first

notify the root bridge.

Once the root bridge is aware of a change in the topology of the network, it sets the TC flag

on the BPDUs it sends out, which are then relayed to all the bridges (TCAs: Topology Change

Acknowledgements) in the network. When a bridge receives a BPDU with the TCA flag bit

set, it reduces its bridging-table aging time to forward delay seconds. This ensures a

relatively quick flush of stale information.




1.12 STP – Convergence Time

• A switched network with STP has converged only when all ports are

either in Blocking or Forwarding State.

• Blocking ports only receive BPDUs.

• Forwarding ports receive BPDUs, they also send and receive traffic.

• When the topology changes, the switches have to recalculate the

spanning-tree process.

• Convergence can take up to 50 seconds. (Max-age=20 sec, Listening

delay 15 sec, Learning delay=15 sec)

• That’s why, amendment needed at STP

• RSTP

• MSTP

In case of a failure:




In case of a failure:

�1) Port physically down: The switch detects loss of carrier and immediately declares the

port down. Since, it was the port with the best BPDU, the switch immediately invalidates

it, and selects the next “best candidate” which is the alternate port as the new root port.

The new port will go through Listening and Learning states, which takes 2 x Forward_Time.

Therefore, the connectivity is restored in 2xForward_Time=30 seconds by default.

�2) Failure receiving BPDUs: The switch does not detect the loss of carrier (for instance, the

uplink is fiber connected to a converter or connects through a hub), and thus the port

remains up. The root port loses the continuous stream of BPDUs. The stored BPDU

information is no longer updated. Based on the default procedure, it takes time Max_Age

to expire the stored information. After this, the switch considers the BPDU stored with the

alternate port, and unblock the new port. It will take another 2xForward_Delay to bring

the port to forwarding state. Therefore, the connectivity is restored in

2xForward_Time+(Max_Age) =50 seconds by default.

�Forward Delay: 15 sec by default. (Listening and Learning states)

�Max Age: 20 sec by default. (When the designated port is up but can not receive any BPDUs

within this period, the alternate port will be enabled for forwarding after listening and

learning states of course.)



2 Rapid Spanning Tree Protocol







2.1 Rapid Spanning Tree Protocol - States

• Defined in IEEE 802.1w LAN Standard

• Disabled, Blocking and Listening Modes are merged in Discarding State

only

STP RSTPIs Port Included in

Active Topology?

Is Port Learning

Mac-Addresses?

Disabled Discarding No No

Blocking Discarding No No

Listening Discarding No No

Learning Learning Yes Yes

Forwarding Forwarding Yes Yes




Active Topology � Topology of the converged switched network.

The RSTP (Rapid Spanning Tree Protocol) is defined in the IEEE 802.w LAN standard.

Compared to the STP, the RSTP only has 3 port states, Discarding, Learning and Forwarding.

This is one reason the RSTP can recalculate the new spanning tree faster than the STP.

Remember the STP had a 30 second delay for both listening and learning port states.




2.2 (Rapid) Spanning Tree Protocol - BPDU Format

• RSTP BPDU is version 2

• Legacy Switches will drop version 2 BPDUs

• TC and TCA parts stay the same in version 2

• The interpretation of the BPDU frame is improved

• More information on BPDU within RSTP

0 7

TC TCAProposal

Port Role

Learning

Forwarding

Agreement







2.3 During Topology Change – BPDU Handling

STP RSTP

BPDU

handling

Non-root bridge only transmits

BPDUs when it receives one on the

root port

Bridge sends BPDU on all ports

BPDU Aging BPDU is aged after the max-age

timer expires (when no BPDU is

received on the port)

BPDUs are used like keepalive

messages (after 3 BPDUs in a row are

missed it ages it out)

Transition to

forwarding

state

Based on timers (Forward Delay and

Max-Age)

Uses a feedback mechanism (no timers

involved) --- Sync Process




BPDUs are used as a keep-alive mechanism between bridges.

Sent in every Hello-Time interval (default=2 sec)

� STP: A non-root switch only relays BPDUs when it receives one on the root port. No

real generation.

� RSTP: The switch generates within the interval even it doesn’t receive any from the

root.

Faster Aging of Information

� If BPDUs are not received after 3 consecutive times, protocol information will be

immediately aged out.

� So, the information is checked with the neighboring switch in RSTP.

� In STP, during convergence time, the problem might have been anywhere on the path to

the root.




2.4 Example: Inferior BPDUs – Convergence for Indirect Links

BPDU

“I am the ROOT”

A

B

C

D

Blocking

Priority = 4096

Priority = 16K

Priority = 32K

D

Listening

Better BPDU

Forwarding




In this case, SW2 has better Bridge ID than SW3.

SW3 blocks the redundant uplink to SW3 (Port B) and elects Port A as the root port. Now

imagine that SW2 detects loss of carrier on the link connected to Root (Port D). The switch

will immediately invalidate the best BPDU stored for Port C, and will assume itself the root

switch of the spanning-tree, as there are no other ports receiving BPDUs. SW2 will start

advertising BPDUs to SW3, setting the designated and the root bridge to itself in the

configuration BPDUs. Those are, by definition, inferior BPDUs, and SW3 will ignore them, as

it still hears better information from Root. SW3 will also keep the previous BPDU associated

with Port B for the duration of Max_Age. When this timer expires, SW3 will start considering

the inferior BPDUs. Port B will move to Listening state, and SW3 will start relaying Root’s

BPDUs to SW2, as those are superior to SW2’s BPDUs. Now, SW2 would detect the better

information on its formerly designated port (Port D) and will cycle the port through

Listening and Learning states. Both switches (SW2 and SW3) will eventually move their

ports into forwarding states, recovering the connectivity. Therefore, it will take Max_Age +

2xForward_Time to recover from indirect link failure. (50 seconds by default).




2.5 Rapid Spanning Tree Protocol - Link Designations

LINK –TYPE (SHARED)

LINK –TYPE (P2P)

EDGE–TYPE (SHARED)

EDGE–TYPE (P2P)







2.6 Topology Change Detection and Propagation

• Only non-edge ports that move to the forwarding state cause TCs

• When RSTP is aware of a TC:

1. It starts a TC While Timer with a value of 2 times of hello-time for all

designated ports and root port. During the TC While Timer count down,

the BPDUs on that ports are sent with a set TC bit including the root

ports.

2. It flushes all Mac-Addresses associated with all ports.

• The initiator of the TC floods as opposed to STP where only the root

did




TC=Topology Change

Switches forward Ethernet frames based on their MAC address tables (filtering tables) that

bind MAC addresses to egress ports. When a change in topology occurs (e.g. a link failure)

the MAC address tables may appear to be invalid, as the paths between switches have

changed. The switches may eventually re-learn the new information, but it may take

considerable time, especially if the traffic is scarce and MAC address aging time is large (5

minutes by default). Based on that, if switch detects a change in the topology (e.g. link

going up or down), it should notify all other switches that something has changed. In

response to this notification, all switches will reduce their MAC address aging time to

Forward_Time (15 seconds by default) effectively hastening the aging process.

In STP:

� Topology changes are signalled via special TC BPDU, which is being sent upstream from the originating switch

(the one that detected the change) to the root switch via the root ports. As the root switch hears the TC

BPDU, it will set TC ACK flag in all its outgoing configuration BPDUs for the duration of Max_Age +

Forward_Time. All switches that see this flag, will set their MAC address tables aging time to Forward_Time.

Once the switch that originated the TC BPDU will hear the TC ACK, it will stop signalling about the topology

change.

� Network performance. Shortening the MAC address table aging time results in less stable topology. When a

switch loses a MAC address, it starts flooding frames for this destination, effectively acting like a hub. If the

flow of packets in your network is not intense enough, the switches may start losing MAC address table

information, resulting in excessive traffic flooding. The issue might become pretty dangerous with high

number of topology changes. Excessive flooding might severely impact your network performance. Note, that

this issue also pertains to L2 topologies that runs RSTP, as the topology changes are handled in the similar

way. In order to reduce the number of topology changes, configure all edge ports in the topology (connected

to hosts, IP Phones, servers) as spanning-tree edge-type ports. Edge-type ports do not generate TC events

when they go up or down.






STP RSTP

Topology

change

Sends TC BPDUs towards root Sends BPDUs (with TC bit set) on

all designated and root ports

Topology

ACKs

Replies with BPDU with TCA bit

set from Root

No acknowledgement (clears MAC

addresses on all ports)


2.7 STP vs. RSTP – Topology Change Behavior




Another reason why RSTP is faster than the STP. In the RSTP if a switch detects

a topology change it communicates it to everybody where in STP it sends it to

the Root switch. Also in the STP there are TCAs (Topology Change

Acknowledges) where in the RSTP they don’t exist.

A little bit of information on how and what the switches exchange. Switches

forward Ethernet frames based on their MAC address tables (filtering tables)

that bind MAC addresses to egress ports. When a change in topology occurs

(e.g. a link failure) the MAC address tables may appear to be invalid, as the

paths between switches have changed. The switches may eventually re-learn

the new information, but it may take considerable time, especially if the

traffic is scarce and MAC address aging time is large (5 minutes by default).

Based on that, if a switch detects a change in the topology (e.g. link going up

or down), it should notify all other switches that something has changed. In

response to this notification, all switches will reduce their MAC address aging

time to Forward_Time (15 seconds by default) reducing the aging process.




2.8 Rapid Spanning Tree Protocol – Sync Process

p0

p1

p2 P3p4

• p0: designated port

• p1: new root port

• p2: alternate port

• p3: ORIGINAL root port

• p4: edge port

2: sync (unchanged)

2: sync (unchanged)

2: sync (block)

1: Proposal3: Agreement, p1 Forwarding

1. Designated Port in discarding or learning state, it sets the proposal bit on BPDUs it

sends out.

2. Switch-A gets a superior information, it sets p1 as root port . Then, Switch-A starts

sync process to see all the ports are updated or not with latest information.

3. After sync, Switch-A sends “agreement” setting the bit at BPDU. --- A copy of the same

BPDU from root switch. This time, the agreement bit is set in BPDU message.

PROCESS COMPLETED

Note: Now p0 and p1 are in forwarding state.

R




STP waits 30 seconds before it transitions to the forwarding state. (When the port is

selected to become a designated port)

During sync process there won’t be any change for two type of criteria:

�Blocking Ports

�Edge Ports

�The proposal agreement mechanism is very fast, because it doesn’t rely on an aging

mechanism and there is no timer for that. The way of handshakes propagates quickly

towards the edge of the network.

�If a designated port in discarding state, sends a proposal and doesn’t receive any

agreement from the port then, it slowly falls back to STP states. Means the stages of

listening and learning and so on... This case can occur when the remote bridge port is in

blocking mode and doesn’t understand any RSTP BPDUs.




2.9 Rapid Spanning Tree Protocol – Convergence

EDGE–TYPEEDGE–TYPE

R

D

D

DR

RD

B

R

SYNC PROCESS

SYNC PROCESS

R

B

B

1. Topology in Orange Links




1. Topology in Orange Links

2. Adding purple line

3. RSTP process starts:

�A negotiation starts between Root (R) and A. As soon as A receives BPDU from R, it

blocks the non-edge root ports. This operation is called sync. Once sync completed, A

authorizes R to put its port in the forwarding state.

�At this stage, the newly blocked ports on A also negotiate a quick transition so called

sync with their neighbor ports with B and C.

�By that time, if there are any edge-type ports, they are not going to be blocked during

the process. For instance, the links on B except the root ports towards A.

�Remember there can not be a loop. As, after the link is set as forwarding between A and

R, the root port(s) will be blocked. Now, the possible loop cut at different location in

the switches and this cut travels down in the network along with the new BPDUs from

the root switch.

�Note: When the new link (Between Switch A and Root) is converged. The BPDU value

sent out from Switch A to Switch C will also change (new link has converged and we have

now a different path-cost to Root). Swicth C is also receiving BPDUs from D. There will

be comparison between received BPDUs about the root path cost. if C is sending a

better one comparing D, the process will restart between the switches A and C. For the

process, see Link Designations slide on Rapid Spanning Tree Protocol Chapter.



3 Multiple Spanning Tree Protocol







3.1 How about Multiple VLAN situation?

VLAN 100VLAN 200

VLAN 200

VLAN 100

(R)STP concludes to block the link between Switch A and Switch C

PC-A PC-B

VLAN 200




(R)STP decisions in selecting what paths form the spanning tree are not based on VLAN

availability. For the best path to the destination, the bandwidth will be evaluated with the

defined cost values and as a result of this the link(s) will be either in a blocked state or not.

That may not be convenient for some VLANs. For example, PC-A wants to communicate

with PC-B, so the path it will take will be switches B, A, Root, D and C.

MSTP was originally defined in IEEE 802.1s but later merged into the IEEE 802.1Q-2005

standard. The idea is that several VLANs can be grouped into a spanning tree “instance” (or

1 VLAN per instance) called MSTI, with each instance having a spanning-tree topology

independent of other spanning-tree instances. Therefore an MSTI can contain any number of

VLANs, but a VLAN can belong to only one MSTI at a time.

.




This architecture provides multiple forwarding paths for data traffic, enables load balancing

and reduces the number of spanning-tree instances required to support a large number of

VLANs.

Therefore, each spanning tree instance (or MSTI) converges separately and has its own root

switch.

This allows for seamless interoperability between areas of the network that do not support

multiple spanning tree processes with others that do.

In the drawing the link between switch A and C is blocked for Vlan 200 [Animation 1] and the

link between switch C and D is blocked for Vlan 100 [Animation 2]. If we take the same

example as before, PC-A wants to communicate with PC-B then in this case the path it will

take will be switches B, A and C.

So what is MSTP?

It is an extension of the RSTP protocol to further develop the usefulness of virtual LANs

(VLANs). Therefore MSTP is VLAN aware.

If there is only one VLAN in the network, single (R)STP works appropriately. If the network

contains more than one VLAN, we can go for MSTP.




3.3 What is MSTP - Multiple Spanning Tree Protocol

• Defines an extension to the RSTP protocol to further develop the usefulness of virtual LANs (VLANs).

• MSTP is VLAN aware

• If there is only one VLAN in the network, single RSTP works appropriately. If the network contains more than one VLAN, we can go for MSTP.

• Here we call one STP as one instance. One loop per instance will be there. One spanning Tree per instance.




If the switches have 1 or more different attributes, they belong to different regions

Each switch running MST in the network has a single MST configuration that consists of these

three attributes:

• An alphanumeric configuration name (Region-Name)

• A configuration revision number (two bytes)

• A 4096-element table that associates each of the potential 4096 VLANs– instance

A common Region Name, Format Selector, and Revision Level are used to logically group

switches into a Region. This allows for greater scalability, since each region now defines the

logical boundary of the spanning tree network.




3.4 Multiple Spanning Tree Protocol - Regions

MST Region

M-records contain individual

parameters about each MSTI

(root bridge ID, root path

cost, etc)

VLANInstances




MSTP allows formation of MST regions that can run multiple MST instances (MSTI).

An MSTP region is a collection of switches, sharing the same view of physical topology

partitioning into set of logical topologies.

The concept of MSTP region allows for bounding STP re-computations. Since MSTIs in every

region are independent, any change affecting MSTI in one region will not affect MSTIs in

other regions. This is a direct result of the fact that M-Record information is not exchanged

between the regions.

Each switch running MST (Multiple Spanning Tree) in the network has a single MST

configuration that consists of the following attributes:

�An alphanumeric configuration name (Region-Name)

�A configuration revision number

�A 4096-element table that associates each of the potential 4096 VLANs

If the switches have 1 or more different attributes, they belong to different regions.

Switches grouped into regions allows for greater scalability, since each region now defines

the logical boundary of the spanning tree network.




3.4 Multiple Spanning Tree Protocol - Regions [cont.]

MST Region

Different MST Regions will be treated as different virtual bridges.

At boundary ports no MSTI BPDUs are sent out, only STP BPDUs are.




The boundary ports of a MST region do not send MSTI BPUs, the M-records, outside the region. This is the

reason that an MST region is seen as one virtual switch.



Module summary

After completing this section, you are able to:

• Describe Spanning Tree Protocol

• Bridge Ids and Root Selection

• BPDU format

• Bridge and Port Definitions


• Describe Rapid Spanning Tree Protocol

• New BPDU format


• Topology Change Behaviour

• Describe Multiple Spanning Tree Protocol

• Vlan Instances

• Regions






STP RSTP MSTP TechEnd of module




Copyright © 2013 Alcatel-Lucent. All Rights Reserved.TAC42059_HO01 Edition I2.0Section 2 · Module 1 · Page 1


Document Historyy

Edition Date Author Remarks

01 Mar/2013 ALU-University Madrid R4.4 – AMS R9.1.10

02 Aug/2013 ALU-University China R4.5/R4.6 – AMS R9.2.30

02 Jan/2014 ALU-University Madrid Only Cosmetic





Page

1 Spanning Tree Protocol 71.1 802.1w – Rapid Spanning Tree Protocol 81.2 802.1s – Multiple Spanning Tree Protocol 91.3 Redundancy is needed- How about loops? 101.4 Bridge and Port Definitions 111.5 ISAM - IP Stack --- xSTP Implementation 121.6 ISAM m-VPLS Implementation 131.7 VLAN Tagging options 141 8 xSTP Configuration and Parameters CLI 151.8 xSTP Configuration and Parameters - CLI 151.9 Basic Configuration - CLI 161.10 MSTP Configuration Example - CLI 171.11 M-VPLS Creation 181.12 STP Parameters 191.13 Ports to be added under STP --- M-VPLS 201.14 Creating MSTP Instances 211.15 xSTP Troubleshooting 242 Link Aggregation 252 1 LAG - Primary port 262.1 LAG Primary port 262.2 LAG – Port Category 272.3 LAG – Auto negotiation 282.4 Physical Ports & Link Aggregation Group Configuration – CLI 292.5 Create LAG 312.6 Add Port to Link Aggregation Group 332.7 Add LAG to a Service (VPLS) 342.8 Link aggregation Troubleshooting 353 NT Redundancy and Load-sharing 373.1 Why is redundancy needed? 383.2 Equipment Protection vs Link Protection 393.3 Where needed? 403.4 Ethernet switch aggregation: RSTP 413.5 Ethernet switch aggregation: MSTP 423.6 Ethernet switch aggregation: MPLS 433.7 Configure NT protection group (only impacting OAM) 443.8 Configure NT protection element (only impacting OAM) 453.9 Show status commands 463.10 Load-sharing – for HiCap LT boards 473 11 Load sharing for legacy LT boards 493.11 Load-sharing – for legacy LT boards 494 Exercises 514.1 Exercise 1 52





Spanning Tree Protocol (802 1d) and its variant RSTP have been developed in order to Spanning Tree Protocol (802.1d) and its variant RSTP have been developed in order to prevent loops which could result in broadcast storms.

Recovery time of STP ~ 50 seconds ( recovery time for RSTP: 100 ms!). STP was designed at a time where recovering connectivity after outage within a minute or so was considered adequate performance

upon reconfiguration, bridge ports must wait for new topology information to propagate through the domain before transitioning from ‘blocking’ to ‘forwarding’ state (30 60 through the domain before transitioning from ‘blocking’ to ‘forwarding’ state (30-60 second expiry timer) hence limitation of 7 hops …

RSTP versus STP:

The main difference between STP and RSTP is in the negotiation between nodes on the network - everything else is identical. In RSTP, the BPDU format has changed due to the consolidation of several aspects of STP to streamline performance. For instance, in STP th fi diff t t t th t t b i hil i RSTP th l th there are five different states that a port can be in, while in RSTP there are only three. Second, there are several points during the negotiation of BPDUs that have been made more efficient. As an example, when sending or receiving BPDUs, the STP system waits for a specific amount of time before acting. In RSTP these delays are reduced or eliminated. Finally, RSTP can detect and reconfigure the logical topology of a network much quicker than STP because of more efficient communication between the nodes. All of these benefits of RSTP result in faster reconfiguration of the network, making 802.1w a better candidate


for eliminating loops in modern Ethernet networks.

Multiple instance spanning tree protocol (MSTP - 802.1s) is not supported yet, but foreseen in the roadmap. This protocol allows run multiple instances of STP over single link e.g. one instance per VLAN.

MSTP is the 802.1s IEEE standard.The idea is that several VLANs can be grouped into a spanning tree “instance”, with each instance having a spanning-tree topology independent of other spanning-tree instances.

This architecture provides multiple forwarding paths for data traffic, enables load balancing and reduces the number of spanning-tree instances required to support a large number of VLANs.VLANs.

A common Region Name,Format Selector, and Revision Level logically group switches into a Region. This allows for greater scalability, since each region now defines the logical boundary of the spanning tree network.

Therefore, each spanning tree instance converges separately and has its own root bridge.

This allows for seamless interoperability between areas of the network that do not support l i l i i h h h dmultiple spanning tree processes with others that do.

Every bridge/switch has a single MST configuration with following attributes:

• Alpha numeric configuration name

• A config revision nr

• Mapping table VLAN – instance


If the switches have 1 or more different attributes, they belong to different regions.

When a broadcast message received in a bridge, it will be flooded to everybody connected. In redundancy networks, this process will result in loops that the switches are not aware of. Which consumes a lot of CPU, bandwidth and resources in the end.

Multicasts are treated as broadcasts by the switches. Broadcast and multicast frames are flooded out all ports except the one on which the frame was receivedflooded out all ports, except the one on which the frame was received.

802.1D Bridge Protocol

• Interconnection of IEEE 802 LANs

• Includes Spanning Tree Protocol (STP)

802.1W Rapid Bridge Protocol

• Amendment to IEEE Std 802.1D

• Rapid Spanning Tree Protocol (RSTP)

M lti l S i T P t l (MSTP)

Copyright © 2013 Alcatel-Lucent. All Rights Reserved.TAC42059_HO01 Edition I2.0

Section 2 · Module 1 · Page 10

Multiple Spanning Tree Protocol (MSTP)

• Provides STP to run on multiple VLANs.

• Originally defined in IEEE 802.1s and later merged into IEEE 802.1Q -2003

Spanning tree works in first instance by selecting a root bridge on the LAN. This particular bridge is elected through the exchange of BPDU.

All ports on the root bridge are known as designated ports and are in Forwarding State. Forwarding state ports can send and receive traffic.

All of the other bridges present are known as non-root bridges, they choose a port known as a root port which sends and receives traffica root port which sends and receives traffic.

On non-root bridges only one port can be designated, all others are blocked. Designated ports forward MAC addresses. Designated ports are selected after the bridge determines the lowest cost path to get to the root bridge.

By using this method, the redundant links are closed down. They can be opened again if there is a change in network topology and the link is needed once more.

PORT ROLES

The Root Port and Designated Port perform the same functionality, but Blocking Ports have two roles: Backup Port and Alternate Port. Spanning Tree Algorithm defines port roles based on BPDUs. Within the value inside BPDU messages, the port can be compared with others and the action can be taken accordingly.

Backup Port: The redundant port for a shared network. This port is not for accessing to the



Root Switch. It provides backup for another part of the shared switched network.

Alternate Port: The interface that we are receiving traffic has better BPDU values to access to the Root Bridge. When the Designated Port fails on the switch then the alternate port will be used for the path.

Untagged MSTP/RSTP protocol packets only

• Only untagged MSTP/RSTP protocols will be supported, therefore all SAPs should have VLAN-Id=0

• Since we also need to support untagged frames for v-VPLS instances, we have an issue because IPD does not allow two SAPs (one for m-VPLS, and one for v-VPLS) on the

t ith VLAN Id 0 hi h i lsame port with VLAN-Id=0, which is normal

Solution for untagged MSTP/RSTP protocol packets

• Introduce a new notation for m-VPLS; SAP Px: no-tag

• “no-tag" refers to untagged RSTP/STP/MSPT protocol packets

• SAP Px: no-tag can only be used for m-VPLS

• Internally, “no-tag" is translated into a VLAN-Id (I.e. 4094 internal communication VLAN) which cannot be assigned to a user v-VPLS

• Rx: VLAN-Id:4094 is added to the untagged RSTP/STP/MSPT protocol packets before sent to m-VPLS application

• Tx: VLAN-Id:4094 is stripped off from the RSTP/STP/MSTP protocol packets before sent out



• Note that reusing internal communication VLAN-Id for this purpose is not an issue since internal communication VLAN will not be visible to IPD (i.e. it would be managed by Internal VLAN Mgnt subsystem)







Spanning Tree Operating Modes Spanning Tree Operating Modes

A preferred STP variant can be configured for the m-VPLS. The following STP variants supported on the 7302 ISAM.

• rstp: Rapid Spanning Tree Protocol (RSTP) compliant with IEEE 802.1D-2004 - default mode.

• dot1w: Compliant with IEEE 802.1w.

• comp-dot1w: Operation as in IEEE 802.1w but backwards compatible with IEEE 802.1d (this mode was introduced for interoperability with some MTU types).

• mstp: Compliant with the Multiple Spanning Tree Protocol specified in IEEE 802.1Q-REV/D5.0-09/200.p p p p g p Q

• pmstp: Provider MSTP mode is implemented according to 802.1ad (provider bridges) . The provider functionality is implemented and the provider edge functionality is not.

While the 7302 ISAM initially uses the mode configured for the m-VPLS, it will dynamically fall back (on a per-SAP basis) to STP (IEEE 802.1D-1998) based on the detection of a BPDU of a different format. A trap or log entry is generated for every change in spanning tree variant.

Some older 802.1W compliant RSTP implementations may have problems with some of the features added in the 802.1D-2004 standard. Interworking with these older systems is improved with the comp-dot1w mode. The differences between the RSTP mode and the comp dot1w mode are: the RSTP mode implements the improved convergence over shared media the RSTP mode and the comp-dot1w mode are: the RSTP mode implements the improved convergence over shared media feature, for example, RSTP will transition from discarding to forwarding in 4 seconds when operating over shared media. The comp-dot1w mode does not implement this 802.1D-2004 improvement and transitions conform to 802.1w in 30 seconds (both modes implement fast convergence over point-to-point links).

In the RSTP mode, the transmitted BPDUs contain the port's designated priority vector (DPV) (conforms to 802.1D-2004). Older implementations may be confused by the DPV in a BPDU and may fail to recognize an agreement BPDU correctly. This would result in a slow transition to a forwarding state (30 seconds). For this reason, in the comp-dot1w mode, these BPDUs contain the port's port priority vector (conforms to 802.1w).

The 7302 ISAM supports two BDPU encapsulation formats and can dynamically switch between these (again on a per SAP



The 7302 ISAM supports two BDPU encapsulation formats, and can dynamically switch between these (again on a per-SAP basis):

• IEEE 802.1D STP

• Cisco PVST

STP Parameters (UNDER a “SAP”)

[no] auto-edge - Enable/disable automatic detection of edge port

[no] edge-port - Configure sap as edge or non-edge port

[no] link type Configure link type of the sap[no] link-type - Configure link type of the sap

mst-instance + Provision a Multiple Spanning Tree instance

[no] path-cost - Configure path-cost

[no] port-num - Configure virtual port number

[no] priority - Configure stp priority

[ ] d E bl /di bl STP d[no] root-guard - Enable/disable STP root-guard

[no] shutdown - Enable/disable spanning tree protocol



















• LAG sub-group

• IPD supports grouping of links for a given LAG into a "subgroup" and amongst the subgroups within a LAG, one subgroup is chosen to be "Active" and within this chosen subgroup links become Active links (the other subgroup's links are either Standby or failed)

LAG b ill t b t d i th fi t l t NANT D• LAG sub-group will not be supported in the first release at NANT-D



• Alarms

• LAG down alarm will be supported

• LAG will be down when all links are down or number of active links reaches/goes below a configured threshold

• A new alarm-type: LAG, and alarm-index should identify the LAGyp , y



• Each LAG instance has its own id and is considered as a new, logical port in all later configuration, the LAG can be referred to as:

lag-<lag-id>

LACP (Link Aggregation Protocol)

• Both active and passive LACP is supportedp pp

• LACP periodic transmission machine supports both the fast (1s) and the slow (30s) periodic time





















Resiliency is the ability to recover from a failure.

• The term may be applied to hardware, software or data

Resiliency always matters when many users are impacted upon failure, so it was always crucial in aggregation and edge networks:

• non-stop forwarding / graceful restart / MPLS…p g g

Historically it was less important in access networks, but that changes now: especially when triple plays takes off, resiliency is crucial in access networks too!



Equipment protection switching protects the system against hardware failures:

e.g. if NT-A fails, there’s a switchover to NT-B. For the NT I/O there’s no redundant equipment (there’s less need for a redundant board, since it contains basically passive components with little chance of failures).

APS = Automatic protection switching

The NE supports line protection and EPS. If a second – redundant – NT unit is installed, EPS provides protection against internal failures of the active NT.

In HighCap NT boards the switching is only impacting OAM (SNMP, CLI, database and software management) while traffic shared between both NT boards in active/active modemanagement), while traffic shared between both NT boards in active/active mode.

Remark: even though the link protection is not exactly the same as the SDH/SONET APS, it is sometimes also called APS.



A/A: Active/Active

A/S: Active/Standby

• From the perspective of resilience, load-sharing can be seen as a generalization of redundancy, since in case of failure of one board the remaining board takes all load.y, g

• Since the regular links on HiCap NT boards are always working in load-sharing mode for user traffic, Link Protection Switching (LPS) is fully decoupled from Equipment Protection Switching (EPS).

• External management traffic can be transmitted via the regular links of both NT boards, though it is processed on the active NT board, as part of such OAM processes as CLI, SNMP, database and software management., g

• The craft connection only works on the active NT board.

• In HighCap NT boards the combined use of Redundancy and Load-sharing (when protection is unlocked) is subject to an ISAM Feature license in the AMS, for which the NE provides the counter.



h l d h d l h h d d h k The slide shows a dual homing scenario where a device is connected to the network via two independent access points (points of attachment). One access point is the primary connection; the other is a standby connection that is activated in case the primary connection fails.

802.1w Rapid Spanning Tree Protocol runs over ISAM uplinks

RSTP runs over ISAM network links, not over subtending links or user links.

RSTP protects against:

• link failure

• aggregation node failure

RSTP doesn’t offer load balancing!

• RSTP can be combined with link aggregation (LACP offers load balancing between the links in a LAG).

• In that case, combined link and NT protection recommended (forced switch-over to “full” backup LAG instead of bandwidth drop upon failure of a defined number of links in the LAG – you can configure the threshold for switchover how many links in the



in the LAG you can configure the threshold for switchover how many links in the LAG must always be operational?)

(Persistency of subscriber management characteristics in 7x50 nodes requires regular exchanging state info between both switches.)

This is also a dual homing situation.

In case of RSTP only one Ethernet switch is active for all VLANs. The other Ethernet switch is standby for all VLANs.

In case of MSTP both Ethernet switches can be active: one for VLAN A and the other for VLAN B.



This is also a dual homing situation.

In case of RSTP only one Ethernet switch is active for all VLANs. The other Ethernet switch is standby for all VLANs.

In case of MPLS again both Ethernet switches can be active: one for Service A and the other for Service B, with very fast recovery time (1000x faster than STP).



CLI: the command to enable/disable equipment protection switch:• configure equipment protection-group <1> admin-status <lock/unlock> eps-

quenchfactor <0..1440000>

• By locking protection-group 1, you disable NT protection.

• The EPS-quench factor is a timer value (in AMS expressed in seconds; in CLI in h d d f d ) Thi b d id li f NT A NT B d hundreds of seconds). This can be used to avoid toggling from NT-A to NT-B and back all the time. If there is a next failure before time out (t < quench timer), there will be no switchover.



CLI: the command to change the switchover mode:

• configure equipment protection-element nt-b redcy-ctrl-status forced_active

• Don’t forget to put it back to normal afterwards to allow automatic switchover





















All Rights Reserved © Alcatel-Lucent @@YEAR


1

Last but one page

Congratulations

You have finished the training

Your feedback is appreciated!

Please feel free to Email your comments to:

[email protected]

Please include the training reference in your email (see cover page)

Thank you!

All Rights Reserved © Alcatel-Lucent @@YEAR@@COURSENAME - Page 1

All Rights Reserved © Alcatel-Lucent @@YEAR@@COURSENAME - Page 2

All rights reserved © Alcatel-Lucent Passing on and copying of this document, use and communication of its contents not permitted without written authorization from Alcatel-Lucent

Documents

TAC42059_V1.1-SG-Ed2.0-PDF_CE