Quick Start Guide Virtual Port Channel (vPC)

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Quick Start Guide Virtual Port Channel (vPC)

Architecture & Solutions GroupUS Public Sector Advanced ServicesMark Stinnette, CCIE Data Center #39151

Date 13 August 2013Version 1.8.2


This presentation will provide end-to-end configurations mapped directly to commonly deployed data center architecture topologies. In this cookbook style; quick start guide; configurations are broken down in an animated step by step process to a complete end-to-end good clean configuration based on Cisco best practices and strong recommendations. Each QSG will contain set the stage content, technology component definitions, recommended best practices, and more importantly different scenario data center topologies mapped directly to complete end-to-end configurations. This QSG is geared for network engineers, network operators, and data center architects to allow them to quickly and effectively deploy these technologies in their data center infrastructure based on proven commonly deployed designs.

This Quick Start Guide (QSG) is a Cookbook style guide to Deploying Data Center technologies with end-to-end configurations for several commonly deployed architectures.


vPC ConfigurationCommonly Deployed Designs :: Single-Sided vPC


Dual-Layer vPC

vPC ConfigurationCommonly Deployed Designs :: Double-Sided vPC


vPC ConfigurationCommonly Deployed Designs :: Hierarchical vPC

Illustration Purposes Only


vPC ConfigurationCommonly Deployed Designs :: Enhanced vPC (EvPC)


Dedicated Layer 3 Infrastructure

vPC Domain

vPC Peer-Keepalive Link

vPC Peer-Link

vPC Peer Device

vPC Member Port

vPC

Orphan Port

vPC VLAN ::VLAN(s) carried over the vPC peer-link and used to communicate via a vPC; As soon as a VLAN is defined on vPC peer-link it becomes a vPC VLAN

non-vPC VLAN ::VLAN(s) that is not part of any vPC and not present on the vPC Peer-Link

vPC

vPC ConfigurationTerminology & Components


vPC is a virtualization technology that presents paired or two Nexus devices as a unique Layer 2 logical node to the access layer devices or endpoints. vPC belongs to Multichassis EtherChannel [MCEC] family of technology.

A virtual port channel (vPC) allows links that are physically connected to two different Cisco Nexus 7000 or 5000 Series devices to appear as a single port channel to a third device. The third device can be a switch, server, firewall, load balancer or any other networking device that supports link aggregation technology.

vPC provides the following technical benefits:• Eliminates Spanning Tree Protocol (STP) blocked ports• Uses all available uplink bandwidth; Layer 2 hashing algorithm • Allows dual-homed servers to operate in active-active mode• Provides fast convergence upon link or device failure• Offers dual active/active FHRP (default gateways) for servers• Each peer device in the vPC domain runs its own control plane, and both devices work independently

Using vPC; you gain immediate operational and architectural advantages:• Simplifies network design• Build highly resilient and robust Layer 2 network• Enables seamless virtual machine mobility and server high-availability clusters• Scales available Layer 2 bandwidth, increasing bisectional bandwidth• Grows the size of the Layer 2 network• vPC feature is included in the base NX-OS software license

vPC also leverages native split horizon/loop management provided by port-channeling technology; meaning a packetentering a port-channel cannot immediately exit that same port-channel.

vPC ConfigurationBenefits Overview


vPC ConfigurationvPC Spanning-Tree :: Recommendations


Feature Benefit OverviewvPC auto-recovery(reload restore)

Increase High-Availability

(1) Provides a backup mechanism in case a vPC peer-link failure followed by a vPC primary peer device failure; (2) Both vPC peer devices reload or DC power outage; but only one vPC peer comes up - this allows one vPC device to assume STP / vPC primary role and bring up all local vPCs in case (auto-recovery reload-delay)

vPC Peer-Gateway Service Continuity Allows a vPC switch to act as the active gateway for packets addressed to the peer router MAC (ie. NAS)

vPC orphan-ports suspend


When vPC peer-links go down, vPC secondary shuts down all the vPC member ports as well as orphan ports. It avoids single attached devices like FW, LB or NIC teamed devices when isolated during vPC peer-link failure

vPC ARP SYNC Improve Convergence Time

Improve Convergence for Layer 3 flows after vPC peer-link is UP or recovers from a failure

vPC Peer-Switch Improve Convergence Time

Virtualize both vPC peer devices so they appear as a unique STP root bridge

vPC Role & System Priority

Service Continuity Manually set vPC system priority to ensure vPC peer devices are the primary devices on LACP. Manually set the vPC role as primary and secondary – deterministic

vPC Peer-keepalive


Option 1 :: use SUP mgmt int on dedicated OOBOption 2 :: use separate L3 Po in dedicated VRF

vPC Delay Restore Service Continuity Delays vPCs member links from bring up on the recovering vPC peer device. This allows for the Layer 3 routing protocols to converge before allowing any traffic on vPC member links; resulting in a more graceful restoration and zero packet loss during the recovery phase. (This feature is enabled by default – 30 seconds)

vPC ConfigurationvPC Feature Configuration


Option 1 Dedicated link(s) in a Layer 3 Port-Channel in its own dedicated VRF (ie. PKAL VRF)Use separate line cards & 1Gig ports are enough, else you burn 10Gig interfaces

Option 2 Use Mgmt0 interfaces off Supervisors to dedicated routable OOB network + use management VRFPeer-Keepalive traffic along with management traffic

Option 3 As a last resort, route the peer-keepalive traffic over the Layer 3 infrastructure + use default VRF

vPC ConfigurationBuilding a vPC Peer-Keepalive Link :: Nexus 7000 Best Practices


Option 1Use Mgmt0 interfaces to dedicated routable OOB network + use management VRFPeer-Keepalive traffic along with management traffic

Option 2 (Nexus 5000 without L3 module)Dedicated link(s) in a separate Layer 2 Port-Channel , have the peer-keepalive peer across to the SVI’s, manually prune those VLANs off the peer-link making those VLANs (non-vPC VLANs), only trunk the peer-keepalive VLAN across this Layer 2 Port-ChannelDue to ISSU checks via the show spanning issue-impact, ISSU will fail, workaround is to disable STP on this dedicated Layer 2 Port-Channel via the spanning-tree port type edge trunk command, assuming you have the global command spanning-tree port type edge bpdufilter default enabledWill burn 10Gig interfaces

Option 2 (Nexus 5000 with L3 module)Dedicated link(s) in a Layer 3 Port-Channel in its own dedicated VRF (ie. PKAL VRF)Use separate interfaces & will burn 10Gig interfaces

vPC ConfigurationBuilding a vPC Peer-Keepalive Link :: Nexus 5000/6000 Best Practices


feature lacp

vlan 1 – 200

vrf context PKAL interface port-channel 1 vrf member PKAL ip address [….]/30 interface e1/1 , e2/1 channel-group 1 mode active

------------------------------------------------------

interface port-channel 2 switchport switchport mode trunk interface e3/1 , e4/1 channel-group 2 force mode active

feature lacp

vlan 1 – 200


------------------------------------------------------

interface port-channel 2 switchport switchport mode trunk interface e3/1 , e4/1 channel-group 2 force mode active

1/12/1

1/12/1

3/14/1

3/14/1

Po1

Po2

Step 1 :: turn on LACP feature Step 2 :: define your vlansStep 3 :: build peer-keepalive Step 4 :: build L2 port channel for peer-link

Create a dedicated VRF for the vPC peer-keepalive link (best practice)

Building a vPC peer-link, follow these guidelines :: (1) Must have Peer-keepalive link up first; ensure the peer-link member ports are 10 Gig interfaces(2) Use a minimum of two 10 Gig ports (M1 up to 8 member ports & F1/F2 up to 16 member ports)(3) Use at least two different line cards to increase high availability of peer-link

7K-1 7K-2

5K-1 5K-2

vPC ConfigurationBuild Peer-Keepalive & Peer-Link Infrastructure


feature vpc

vlan 1 – 200

spanning-tree pathcost method longspanning-tree port type edge bpduguard defaultspanning-tree port type edge bpdufilter defaultno spanning-tree loopguard default

spanning-tree vlan 1-200 priority 0spanning-tree pseudo-information vlan 1-200 root priority 4096 vlan 1-100 designated priority 8192 vlan 101-200 designated priority 16384

vpc domain 1 role priority 1 system-priority 4096 peer-keepalive destination [….] source [….] vrf PKAL peer-switch peer-gateway auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize

feature vpc

vlan 1 – 200


spanning-tree vlan 1-200 priority 0spanning-tree pseudo-information vlan 1-200 root priority 4096 vlan 1-100 designated priority 16384 vlan 101-200 designated priority 8192

vpc domain 1 role priority 2 system-priority 4096 peer-keepalive destination [….] source [….] vrf PKAL peer-switch peer-gateway auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize

Hard set the Nexus 7K on the left vPC role primary and Nexus 7K on the right vPC role secondary (deterministic)

Step 1 :: turn on vpc feature Step 2 :: configure spanning-tree defaultsStep 3 :: configure spanning-tree vlan root prioritiesStep 4 :: configure vpc domain (per best practices)

Make the Nexus 7Ks control LACP establishment for all port-channels; (lowest) vpc domain id + system priority

Setup the peer-keepalive; use the correct VRF accordingly

Enable peer-switch; when activated both vPC peer devices must have the same STP priority set for all vPC VLANs – making them appear as a unique STP root bridge

Enable peer-gateway, auto-recovery, delay restore, and ip arp synchronize (per best practice) … see Strong Recommendations & Key Notes sections

(Optional Config) – when using vPC peer-switch in a ‘hybrid’ environment use the spanning-tree pseudo-information to load balance VLANs across the 2 peer devices

7K-1 7K-2

5K-1 5K-2

vPC ConfigurationBuild STP & vPC Domain Configuration


feature lacpfeature vpc

vlan 1 – 200


------------------------------------------------------

interface port-channel 2 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type network vpc peer-link interface e3/1 , e4/1 channel-group 2 force mode active


vlan 1 – 200


------------------------------------------------------

interface port-channel 2 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type network vpc peer-link interface e3/1 , e4/1 channel-group 2 force mode active

peer-link

Always perform VLAN pruning on vPC peer-link with the allowed list of vPC VLANs; vPC VLANs must also be pruned on the vPC member port s as well

Bridge Assurance is enabled by default when configuring vPC peer-link (spanning-tree port type network); Do NOT disable it on the vPC peer-link

Step 1 :: enable vPC peer-link on the L2 port channel

7K-1 7K-2

5K-1 5K-2

vPC ConfigurationComplete the Peer-Link Configuration


feature lacp

vlan 1 – 200

vrf context management ip route 0.0.0.0/0 [….]

interface mgmt0 ip address [….]/24 interface port-channel 1 switchport switchport mode trunk interface e1/1 - 2 channel-group 1 force mode active

feature lacp

vlan 1 – 200

vrf context management ip route 0.0.0.0/0 [….]

interface mgmt0 ip address [….]/24

interface port-channel 1 switchport switchport mode trunk interface e1/1 - 2 channel-group 1 force mode active

OOB

1/11/2

1/11/2

mgmt0 mgmt0

Step 1 :: turn on LACP feature Step 2 :: define your vlansStep 3 :: build L2 port channel for peer-link

peer-keepalive linkUse Mgmt0 interfaces to dedicated routable OOB network + use management VRF (configured during initial device setup); includes Peer-Keepalive traffic along with management traffic

7K-1 7K-2

5K-1 5K-2

vPC ConfigurationBuild Peer-Keepalive & Peer-Link :: Access Layer


vpc domain 1 role priority 1 system-priority 4096 peer-keepalive destination [….] source [….] vrf management peer-switch peer-gateway auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize

vpc domain 1 role priority 2 system-priority 4096 peer-keepalive destination [….] source [….] vrf management peer-switch peer-gateway auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize


vlan 1 – 200


vpc domain 10 role priority 1 system-priority 8096 peer-keepalive destination [….] source [….] vrf management auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize


vlan 1 – 200


vpc domain 10 role priority 2 system-priority 8096 peer-keepalive destination [….] source [….] vrf management auto-recovery auto-recovery reload-delay delay restore 30 ip arp synchronize

OOB

Step 1 :: turn on vpc feature Step 2 :: configure spanning-tree defaultsStep 3 :: configure vpc domain (per best practices)

Always use a different domain ID in a double-sided vPC topology; once configured, both peer devices use the vPC domain ID to automatically assign a unique vPC system MAC address; which is used as part of the LACP protocol

Manually set vPC system priority to ensure vPC peer devices are the primary devices on LACP at the aggregation layer or not the primary devices on LACP at the access layer

7K-1 7K-2

5K-1 5K-2

vPC ConfigurationBuild vPC Configuration :: Access Layer



vlan 1 – 200

interface port-channel 1 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type network vpc peer-link

interface e1/1 - 2 channel-group 1 force mode active


vlan 1 – 200

interface port-channel 1 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type network vpc peer-link interface e1/1 - 2 channel-group 1 force mode active

OOB

peer-link

7K-1 7K-2

5K-1 5K-2

Always perform VLAN pruning on vPC peer-link with the allowed list of vPC VLANs; vPC VLANs must also be pruned on the vPC member port s as well

Bridge Assurance is enabled by default when configuring vPC peer-link (spanning-tree port type network); Do NOT disable it on the vPC peer-link

Step 1 :: enable vPC peer-link on the L2 port channel

vPC ConfigurationComplete Peer-Link Configuration :: Access Layer


interface port-channel 10 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal spanning-tree guard root vpc 10 interface e1/13 , e2/13 channel-group 10 force mode active port-channel load-balance src-dst ip-l4port-vlan

interface port-channel 10 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal spanning-tree guard root vpc 10 interface e1/13 , e2/13 channel-group 10 force mode active

port-channel load-balance src-dst ip-l4port-vlan

interface port-channel 10 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal vpc 10 interface e1/9 , e1/10 channel-group 10 force mode active port-channel load-balance src-dst ip-l4port-vlan

interface port-channel 10 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal vpc 10 interface e1/9 , e1/10 channel-group 10 force mode active

port-channel load-balance src-dst ip-l4port-vlan

vPC 10

1/9 1/10 1/101/9

1/13 2/13 2/131/13

7K-1 7K-2

5K-1 5K-2

The configuration of the vPC member port must match on both vPC peer devices. If there is a inconsistency, a VLAN or the entire port channel may suspend (depending on type-1 or type-2 consistency check for the vPC member port). Use the same vPC ID as the port channel ID for ease of configuration, monitoring, and troubleshooting

Use source-destination, IP, L4 port and VLAN as fields for the port channel load balancing hashing algorithm; this improves fair usage of all member ports forming in the port channel

Step 1 :: enable vPC on the member portsStep 2 :: enable spanning-tree port configurationsStep 3 :: change port channel load balancing method

Configure vPC member port as spanning-tree port type normal

Keep Spanning Tree protocol root function on the aggregation layer of the network; For each vPC peer device, configure root guard on ports connected to access devices

vPC ConfigurationBuild Double-Sided vPC


interface port-channel 20 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal spanning-tree port guard root vpc 20 interface e3/13 channel-group 20 force mode active interface port-channel 30 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type edge trunk vpc 30 interface e3/14 channel-group 30 force mode active

interface port-channel 20 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type normal spanning-tree port guard root vpc 20 interface e3/13 channel-group 20 force mode active interface port-channel 30 switchport switchport mode trunk switchport trunk allowed vlan 1-200 spanning-tree port type edge trunk vpc 30 interface e3/14 channel-group 30 force mode active

interface port-channel 20 switchport switchport mode trunk switchport trunk allowed vlan 1-200 interface e1/25 , e1/26 channel-group 20 force mode active

vPC 20 vPC 30

3/13 3/14 3/143/13

1/25 1/26

7K-1 7K-2

Step 1 :: enable vPC on the member ports + enable spanning-tree port configurations accordingly

vPC ConfigurationBuild vPC :: Standalone Switch & LACP Enabled Server


feature lacpfeature fex

fex 100 pinning max-links 1fex 199 pinning max-links 1

interface port-channel 100 switchport mode fex-fabric vpc 100 fex associate 100


interface e1/28 channel-group 100


interface port-channel 1000 switchport mode trunk switchport trunk allowed vlan 10, 20 spanning-tree port type edge trunk interface e100/1/1 , e199/1/1 channel-group 1000 force mode active

feature lacpfeature fex

fex 100 pinning max-links 1fex 199 pinning max-links 1





interface port-channel 1000 switchport mode trunk switchport trunk allowed vlan 10, 20 spanning-tree port type edge trunk interface e100/1/1 , e199/1/1 channel-group 1000 force mode active

vPC 10

Po 1000

vPC 100 vPC 1991/28 1/29 1/291/28

100/1/1

FEX 100

199/1/1

FEX 199

7K-1 7K-2

5K-1 5K-2

Notice in the 5k/2k EvPC topology you DON’T need the vPC command under the port channel towards the server

vPC ConfigurationBuild Enhanced vPC :: Nexus 5000 & Nexus 2000 FEX


install feature-set fex

feature lacpfeature-set fex

fex 199 pinning max-links 1

interface port-channel 199 switchport mode fex-fabric fex associate 199

interface e5/28, e6/28 switchport mode fex-fabric fex associate 199 channel-group 199

interface port-channel 1000 switchport mode trunk switchport trunk allowed vlan 10, 20 spanning-tree port type edge trunk vpc 1000 interface e199/1/1 channel-group 1000 force mode active

install feature-set fex

feature lacpfeature-set fex

fex 199 pinning max-links 1

interface port-channel 199 switchport mode fex-fabric fex associate 199

interface e5/28, e6/28 switchport mode fex-fabric fex associate 199 channel-group 199

interface port-channel 1000 switchport mode trunk switchport trunk allowed vlan 10, 20 spanning-tree port type edge trunk vpc 1000 interface e199/1/1 channel-group 1000 force mode active

vPC 1000

5/28 6/28 6/285/28

199/1/1

FEX 199

199/1/1

FEX 199

7K-1 7K-2

Po 199 Po 199

FET is an optical transceiver that provides a highly cost-effective solution for connecting FEX to its parent switch (7k, 5k, 6k). Note that FET can only be used to connect Fabric links between the Fabric Extender and the parent switch; FET-10G must be connected to another FET-10G)

Straight-Through Topology(only supported topology between 7k & 2k FEX) Default VDC OnlyDefault VDC Only

Notice in the 7k/2k Straight-through topology you need the vPC command under the port channel towards the server

vPC ConfigurationBuild Straight-Through vPC :: Nexus 7000 & Nexus 2000 FEX


feature interface-vlanfeature hsrp

interface port-channel 80 switchport mode trunk switchport trunk allowed vlan 100, 200 spanning-tree port type edge trunk vpc 80 interface e6/13 channel-group 80 force mode active interface vlan 200 ip address 20.20.20.5/24 no ip redirect hsrp 200 preempt priority 110 ip 20.20.20.254 ip route 10.10.10.0/24 20.20.20.1

feature interface-vlanfeature hsrp

interface port-channel 80 switchport mode trunk switchport trunk allowed vlan 100, 200 spanning-tree port type edge trunk vpc 80 interface e6/13 channel-group 80 force mode active interface vlan 200 ip address 20.20.20.6/24 no ip redirect hsrp 200 preempt ip 20.20.20.254 ip route 10.10.10.0/24 20.20.20.1

interface GigabitEthernet0/0, Ge0/1 channel-group 80 mode active no nameif no secruity-level no ip address

interface port-channel 80 port-channel load-balance vlan-src-dst-ip no nameif no secruity-level no ip address

vPC 806/13

0/0 0/1

6/13

interface port-channel 80.100 vlan 100 nameif inside secruity-level 99 ip address 10.10.10.1 255.255.255.0 standby 10.10.10.2

interface port-channel 80.200 vlan 200 nameif outside secruity-level 1 ip address 20.20.20.1 255.255.255.0 standby 20.20.20.2

route outside 0.0.0.0 0.0.0.0 20.20.20.254

Subnet 10.10.10.0 /24 is serviced by the ASA in this example

See VMDC Architecture for more virtual firewall configuration use cases and best practices

7K-1 7K-2

ASA-5585-X

vPC ConfigurationBuild a vPC :: ASA Firewall Appliance


Separate Layer 3 (routed traffic) and Layer 2 (bridged traffic) infrastructure. Use dedicated Layer 3 point-to-point link between the vPC peer devices for backup path to core

CAN’T Dynamically route over a vPC – road mapped in version 7.x

Use a dedicated Layer 2 port-channel trunk for non-vPC VLAN and create dedicated VLAN/SVI to established a Layer 3 relationship (note those VLANS are not on the peer-link – manually pruned off)

Firewalls attached in a vPC; use static routing1. ASA static route to HSRP on Nexus2. Nexus static route to ASA VIP

Firewalls attached in a VRF sandwich; separate vPC attachment

vPC ConfigurationvPC Layer 2 & Layer 3 Separation :: Designs


featue lacpfeature ospffeature interface-vlanfeature hsrp

vlan 1 – 200

interface loopback0 ip address [….]/32

router ospf 1 router-id [….] log-adjacency-changes detail auto-cost reference-bandwidth 100Gbps

interface port-channel 5 ip address [….]/30 ip router ospf 1 area 0.0.0.0 ip ospf network point-to-point

interface e1/32, e2/32 channel-group 5 force mode active

interface e3/32 ip address [….]/30 ip router ospf 1 area 0.0.0.0 ip ospf network point-to-point interface vlan 100 ip address [10.10.10.2]/24 no ip redirects ip router ospf 1 area 0.0.0.10 ip ospf passive-interface hsrp 100 preempt priority 110 ip [10.10.10.1]

featue lacpfeature ospffeature interface-vlanfeature hsrp

vlan 1 – 200

interface loopback0 ip address [….]/32

router ospf 1 router-id [….] log-adjacency-changes detail auto-cost reference-bandwidth 100Gbps

interface port-channel 5 ip address [….]/30 ip router ospf 1 area 0.0.0.0 ip ospf network point-to-point

interface e1/32, e2/32 channel-group 5 force mode active

interface e3/32 ip address [….]/30 ip router ospf 1 area 0.0.0.0 ip ospf network point-to-point interface vlan 100 ip address [10.10.10.3]/24 no ip redirects ip router ospf 1 area 0.0.0.10 ip ospf passive-interface hsrp 100 preempt ip [10.10.10.1]

1/322/32 2/32

1/32

7K-1 7K-2

Use dedicated Layer 3 point-to-point link between the vPC peer devices for backup path to core

vPC 10

5K-1 5K-2

3/32 3/32

Define the SVI associated with HSRP as passive routing interface in order to avoid forming routing adjacency over vPC peer-link

Define vPC primary peer device as the active HSRP instance and vPC secondary peer device as the standby HSRP (from control plane standpoint) for ease of operations

Disable ip redirect (no ip redirect) on the interface VLAN where HSRP is configured

vPC ConfigurationBuild Layer 3 Routing & FHRP :: Dedicated Layer 3 Infrastructure


Failure 1 :: Peer-Keepalive failsFailure 2 :: Peer-Link fails on AggregationFailure 3 :: Peer-Link fails on Access LayerFailure 4 :: Peer-Keepalive fails + Peer-Link fails (Split Brain)

Role Prima

ryRole Secondary

Role Prima

ryRole Secondary

Black hole traffic to single attached devices connected to vPC Peer device with secondary role

When PKL link fails and PL fails ( in this order ) , you have a dual active situation , while both links are down , the primary vPC peer device remains primary and your secondary vPC device becomes operational primary In a vPC environment only operational primary switch behaves as STP root and processes BPDU and your secondary switch do not process BPDUs ( this is regardless of whichever switch is configured as STP root ) Existing flows continue to be forwarded as before the failure; but new flows learning are impaired and uncertain forwarding (or broken state) for new flows will be observed.So when the links comes back up, the originally primary switch will see that, there is an existing operational primary switch (originally secondary) which is behaving like an STP root and processing BPDUsIf the originally primary switch tries to reclaim the primary role at this point, that would mean more convergence time while operational root role is being switched, hence we do not try to reclaim the vpc primary (and acting STP root ) role back to avoid more convergence times

Role Operational Primarynothing happens – no traffic loss

vPC member ports are shut down and all the vPC VLAN interfaces (SVIs) are shut down; meaning no more L3 advertisements – all this happens on the secondary vPC peer device

vPC ConfigurationvPC Failure Scenarios :: 7k & 5k


Failure 1 :: Peer-Link fails on FEX Parent Switch at Access Layer Failure 2 :: Single FEX Fails or Power Loss

Role Prima

ryRole Secondary

Role Prima

ryRole Secondary

Black hole traffic to devices connected to single FEX

No traffic loss – Only the vPC members are shut down northbound facing the Aggregation Layer and the NIF interfaces are lost on the FEX facing the secondary vPC peer device – all traffic will be forward from both FEXs to the primary vPC peer device

Single Attached hosts connected to the FEX are unaffected

5K Parent switches have lost communication to the failed FEX; resulting all host traffic will forward out the secondary FEX. Minimal to no traffic loss when hosts are dual attached in LACP; Active / Standby NIC teaming will failover over to the secondary FEX

Active / Standby NIC teaming will failover over to the secondary FEX

vPC ConfigurationvPC Failure Scenarios :: 5k & 2k FEX


Bridge Assurance prevents a spanning-tree domain from failing in an “open” state. When a port configured for Bridge Assurance stops receiving BPDU’s, the port transitions into a “blocking” state as opposed to remaining in a “forwarding” state. This “closed” state reduces the likelihood for mis-configured devices from creating STP loops.

‘spanning-tree bridge assurance’ is enabled by default for all ‘network’ port types

Specifies bi-directional transmission of BPDUs on all ports of type “network”.

Protects against unidirectional links and peer switch software issues

Provides IGP like hello-dead timer behavior for Spanning Tree

In all versions of NX-OS, available in IOS on the Catalyst 6500 beginning 12.2(33) SXI

Recommended in STP topologies

Not recommend in vPC topologies; only on the peer-link (default)

Without Bridge Assurance

With Bridge Assurance

vPC ConfigurationvPC Bridge Assurance


There are two types of consistency checks :Type-1 :: Puts peer device or interface into a suspended state to prevent invalid packet forwarding behavior. With vPC Graceful Consistency check, suspension occurs only on the secondary peer device.Type-2 :: Peer device or Interface still forward traffic; however they are subject to undesired packet forwarding behavior.

Type 1 and Type 2 consistency check apply both for global configuration and for vPC interface configuration.

show vpc consistency-parameters global – (displays global type-1 consistency parameters)

Parameter Name Value

Spanning Tree Protocol (STP) mode RPVST or MST

STP Enable/Disable state per VLAN Yes / No

STP region configuration for MST Region name, revision, instance to VLAN mapping

STP global settings Bridge Assurance settingsPort type settingsLoop guard settingsBPDU filter settingsMST simulate PVST enable / disable

show vpc consistency-parameters interface port-channel [id] – (displays interface type-1 consistency parameters)


Port channel LACP mode ON, ACTIVE, PASSIVE

Link speed & duplex per port channel Speed in mpbs & Half / Full duplex

Switchport mode per port channel Trunk / Access, native VLAN

STP interface settings Port type settingLoop GuardRoot Guard

MST Simulate PVS Enable / Disable

MTU per port channel Maximum transmission Unit (MTU) value

vPC ConfigurationChecking vPC Configuration Consistency :: Type 1 & Type 2




If any of the vPC Type-2 parameters listed in the table below are not configured identically on both vPC peer devices, the inconsistent configuration can cause undesirable behavior in the traffic flow

Type-2 consistency check parameters


MAC aging timers MAC aging timer for a particular VLAN should be the same on both vPC peer devices

Static MAC entries Static MAC entries in a particular VLAN should be applied on both vPC peer devices

VLAN interface (switch virtual interface [SVI]) Each peer device must have a VLAN interface configured for the same VLAN on both ends, and this VLAN interface must be in the same operational state

ACL Configuration and parameters ACL configuration should be identical on both vPC peer devices

QoS Configuration and parameters QoS configuration should be identical on both vPC peer devices

STP interface settings BPDU filter, Link type (auto, point-to-point, shared), Cost, Port-priority, STP interface setting should be identical on both vPC peer devices

VLAN Database You must create all VLANs on both the primary and secondary vPC peer devices, or the VLAN will be suspended. Those VLANs configured on only one peer device do not pass traffic using the vPC or vPC peer-link

Port security NAC, Dynamic ARP Inspection, IP source guard, port security must be identical on both vPC peer devices

Cisco TrustSec Cisco TrustSec configuration should be identical on both vPC peer devices

DHCP snooping DHCP snooping configuration should be identical on both vPC peer devices

IGMP snooping IGMP snooping configuration should be identical on both vPC peer devices

HSRP HSRP configuration should be identical on both vPC peer devices

PIM PIM configuration should be identical on both vPC peer devices

GLBP GLBPconfiguration should be identical on both vPC peer devices

All routing protocol configurations Routing configuration should be consistent on both vPC peer devices



• Always use different domain ID in double-sided vPC topology • Operations perspective, define vPC primary on the left Nexus and vPC secondary on the right Nexus (role priority) • When configuring large number of VLANs in a vPC environment, use the range command (vlan x-z) vs. individually

configuring one at a time• Create a dedicated VRF for the vPC peer-keepalive link (ie. vrf context PKAL)• When building a vPC peer-link, follow these guidelines

• Must have Peer-keepalive link up first; ensure the peer-link member ports are 10 Gig interfaces• Use a minimum of two 10 Gig ports (M1 up to 8 member ports & F1/F2 up to 16 member ports)• Use at least two different line cards to increase high availability of peer-link• Use dedicated mode 10 Gig ports with M1 32 line card vs. shared mode ports• Split vPC and non-vPC VLANs on different interswitch port channels• Don’t insert any device between vPC peers; a peer-link is a point-to-point link

• Any vPC VLAN allowed on the vPC member port MUST be allowed on the vPC peer-link• Always perform VLAN pruning on vPC peer-link with allowed list of vPC VLAN; vPC VLAN must have been pruned on the

vPC member port previously• If the M1 32 is used for both the vPC peer-link and L3 uplinks to L3 Core, use vPC object tracking feature• When building a vPC member port, follow these guidelines

• The configuration of the vPC member port must match on both vPC peer devices• If there is a inconsistency, a VLAN or the entire port channel may suspend (depending on type-1 or type-2

consistency check for the vPC member port)• Use the same vPC ID as port channel ID for ease of configuration, monitoring, and troubleshooting• With the M1 Series line card :: there can be up to 8 active ports bundled – resulting a 16-way port channel to be

built for the whole vPC• With the F1/F2 Series line card :: there can be up to 16 active ports bundled – resulting a 32-way port channel to

be built for the whole vPC• Do not mix different port types (M1, F1, F2) in the same vPC member port; this is not allowed by the software• Both sides of the vPC member ports must be of the same port type

vPC ConfigurationStrong Recommendation and Key Notes


• The vPC peer-keepalive link carries periodic heartbeat (UDP 3200) between vPC peer devices. It is used at the boot up of the vPC systems to guarantee both peer devices are up before forming vPC domain and also when vPC peer-link fails to down state; in the latter case, vPC peer-keepalive link is leveraged to detect split brain scenario (both vPC peer devices are active–active) [when vPC peer-link is down, there is no more real time synchronization between the 2 peer devices so vPC systems must react to this active-active situation; this is done by shutting down vPC member ports on secondary peer device].

• The vPC peer-keepalive link is a pre-requisite for the vPC domain to form initially (ie. prior to the vPC peer-link configuration + if peer-link is initial up before peer-keepalive is up)

• vPC has 3 timers; hold-timeout (default 3 sec), timeout (default 5s), hello interval (default 1s). The hold-timeout starts once the vPC peer link goes to a down state; during this time period the secondary vPC peer will ignore any peer-keepalive hello messages. During the timeout period, the secondary vPC peer device will look for vPC peer-keepalive hello messages from the primary vPC peer device. If a single hello is received, the secondary vPC peer concludes that there must be a dual active scenario and therefore will disable all its vPC member ports (that is, all port-channels that carry the keyword vpc). Command line configuration to modify vPC timers is (under vPC domain configuration context): peer-keepalive destination ipaddress [source ipaddress | hold-timeout secs | interval msecs {timeout secs}] The default values are ok in most situations.

vPC peer link is down !

Keepalive Hold Timeout

Keepalive Timeout



• Always enable vPC peer-gateway in the vPC domain (on both peer devices), even if there is no end device using this feature (devices that don’t perform standard ARP request for their default IP gateway), there is no side effect enabling it

• (Corner Case) always use vPC peer-gateway exclude-vlan when a transit VLAN (over vPC peer-link) is used in the vPC domain, this is applicable only for mixed chassis mode (M1/F1) with peer-link on F1 ints; note only static routing supported

• Always enable vPC ARP sync on both vPC peers; performs a bulk ARP sync, improves convergence time for L3 flows• Always enable vPC delay restore on both vPC peer devices and tune the timer according based on the network profile• Always enable vPC graceful type-1 check on both vPC peer devices; graceful consistency-check; (enabled by default)• Always enable vPC auto-recovery on both vPC peer devices• Always enable vPC auto-recovery reload-delay on both vPC peer devices (note the vPC auto-recovery reload-delay

deprecates the previous feature called vPC reload restore)• Use vPC orphan port suspend when single-attached devices connected to a vPC domain need to be disconnected from

the network when vPC peer-link fails• Always use a different domain ID in a double-sided vPC topology; once configured, both peer devices use the vPC

domain ID to automatically assign a unique vPC system MAC address; which is used as part of the LACP protocol• vPC role is non-preemptive so vPC operational role is the most relevant of the information per table below

• With NX-OS 6.1 and prior releases, always use identical line cards on either side of the vPC Peer Link and vPC member ports (legs to downstream device)

• Starting in NX-OS 6.2, always use identical line cards on either side of the vPC Peer Link and vPC member ports (legs to downstream device) when M1/M2 & F2E

• Starting in NX-OS 6.2, VDC type must match between the 2 vPC peer devices when F2 & F2E are used in same VDC; meaning its ok to have F2 on vPC peer device 1 and F2E on vPC peer device 2 for the vPC Peer Link or vPC member ports. Note: in a F2 & F2E type of design; only features related to F2 apply (lowest common denominator)



• Use LACP protocol when connecting access devices to vPC domain (channel-group [x] mode active• Use LACP when available for graceful failover and misconfiguration protection• LACP mode active on both sides of the port channel • If access device does not support LACP, use manual bundling (channel-group [x] mode on)• If the downstream access switch is a Cisco Nexus device, enable LACP graceful-convergence (its on by default)• If the downstream access switch is NOT is a Cisco Nexus device, disable LACP graceful-convergence • Use source-destination, IP, L4 port and VLAN as fields for the port channel load balancing hashing algorithm; this

improves fair usage of all member ports forming in the port channel• When possible, always dual-attach access devices to a vPC domain using a port channel• When connecting a single-attached access device to a vPC domain using a vPC VLAN, always connect it to the vPC

primary peer device; reason is when if the vPC peer-link fails down any single attached device connected to the secondary peer device (and using vPC VLAN) will become completely isolated with the rest of the network

• Single Attached Recommendations (descending order of priority):• Connect access device to an intermediate switch which is dual-attached to a vPC domain• Connect single-attached device to a vPC domain using non-vPC VLAN (must also create an inter-switch link

between the 2 peer devices to transport non-vPC VLAN• Connect single-attached device to a vPC domain using vPC VLAN and leveraging vPC peer-link

• In a double-sided vPC topology, all interconnect links between the 2 vPC domains MUST belong to the same vPC ID; all links form a unique vPC (on both sides of the 2 vPC domains)

• LACP port suspend :: By default, LACP sets a port to the suspended state if it does not receive an LACP PDU from the peer (ie a server or host). In some cases, although this feature helps in preventing loops created due to misconfigurations, it can cause servers to fail to boot up because they require LACP to logically bring up the port. You can put a port into an individual state by using the lacp suspend-individual command.

• On the Nexus 5000 this feature is disabled (no lacp suspend-individual) for servers connecting via LACP; on the Nexus 7000 this feature is enabled by default (lacp suspend-individual)



• Recommended Spanning Tree Protocol Configuration with vPC• Spanning Tree protocol must remain enabled for all VLANs (even if all access devices are vPC attached to the vPC

domain); Do NOT disable spanning-tree protocol• Use MST with vPC if you need to build a large L2 domain; Plan ahead to avoid future configuration changes that

can trigger vPC type-1 consistency failure• Implement consistent STP mode in the same L2 domain, ensure that all switch in your L2 domain are running with

Rapid-PVST+ (default) or MST to avoid slow Spanning Tree convergence (30 seconds or more)• Perform VLAN pruning on vPC member ports to reduce internal resource consumption• Keep Spanning Tree protocol root function on the aggregation layer of the network (aggregation vPC domain)• For each vPC peer device, configure root guard on ports connected to access devices• Bridge Assurance is enabled by default when configuring vPC peer-link (spanning-tree port type network); Do NOT

disable it on the vPC peer-link• It is not necessary to enable Bridge Assurance on the vPC (members ports in the vPC) – configure vPC member

port as spanning-tree port type normal• Configure port fast (edge or edge trunk port type) on the host facing interfaces to avoid slow Spanning Tree

protocol convergence (30 seconds or more) when port transitions to an up state• Configure BPDU guard on host facing interfaces to block any BPDU sent from the host (access switch port

receiving the BPDU will be put in errdisable mode) – enable BPDU guard globally• Always define the vPC domain as the STP root for all VLANs in that domain (configure aggregation vPC peer

devices as the STP root primary and STP root secondary) – enforce this rule with root guard on vPC peer device ports connected to another L2 switch

• IF the vPC peer-switch is activated, both vPC peer devices MUST have the SAME spanning tree configuration (same priority for all vPC VLANs) – recommendation to activate vPC peer-switch in the environment

• Do not enable Loop guard on vPC (disabled by default)• When using vPC peer-switch in a hybrid environment use the spanning-tree pseudo-information to load balance

VLANs across the 2 peer devices• Enable UDLD in normal mode on vPC peer-link and vPC member ports



• Layer 3 and vPC Guidelines and Recommendations• Use separate Layer 3 link(s) to connect to L3 devices (like a router or firewall in routed mode) to a vPC domain;

use individual Layer 3 links for routed traffic and a separate Layer 2 port-channel for bridged traffic if both routed and bridged traffic are required

• Always build a Layer 3 backup routed path for the vPC domain in order to increase network resilience and availability; use an OSPF point-to-point adjacency (or equivalent L3 protocol) between the 2 vPC peer devices to establish a L3 backup path to the core in case of uplink failure

• Do NOT use a Layer 2 vPC to attach Layer 3 devices to a vPC domain unless the Layer 3 device can statically route to the HSRP address configured on the vPC peer devices

• You can’t dynamically route over a vPC• Layer 3 backup routing path options (descending order of preference)

• Use dedicated Layer 3 point-to-point link between the vPC peer devices for backup path to core• Use a dedicated Layer 2 port-channel trunk for non-vPC VLAN and create dedicated VLAN/SVI to

established a Layer 3 relationship (note those VLANS are not on the peer-link)• HSRP / VRRP Guidelines and Recommendations

• When running HSRP/VRRP in active-active mode (data plane standpoint), aggressive timers can be relaxed; use the default HSRP/VRRP timers

• Define the SVI associated with HSRP/VRRP as passive routing interface in order to avoid forming routing adjacency over vPC peer-link

• Define vPC primary peer device as the active HSRP/VRRP instance and vPC secondary peer device as the standby HSRP/VRRP (from control plane standpoint) for ease of operations

• Disable ip redirect (no ip redirect) on the interface VLAN where HSRP/VRRP is configured. • Do NOT use HSRP/VRRP object tracking in a vPC domain



• Recommendations for Multilayer vPC for DCI Solution• Use different vPC domain-id for each vPC domain (DC1: vPC domain for aggregation, vPC for DCI. DC2: vPC domain for aggregation,

vPC for DCI)• For each data center, interconnect the aggregation vPC domain to the DCI vPC domain using a vPC (double-sided topology)• Interconnect the 2 data centers using a vPC (vPC between DCI vPC domain in site 1 and site 2)• Enable BPDU filter on the vPC used for DCI (under the port-channel configuration, activate the following command: spanning-tree

bpdufilter enable) to avoid BPDU propagation• Configure the vPC used for DCI as spanning-tree port type edge (i.e port fast) to fasten port state forwarding mode when port is

operationally up• Remember by default vPC peer-link runs in spanning-tree port type network i.e bridge assurance is activated on the link• Configure root guard on aggregation vPC domain (more exactly on vPC between this vPC domain and DCI vPC domain). STP root must

remain on aggregation vPC domain on each side of the data center• No loop must exist outside the vPC domains.• Do not use Layer 3 peering between data centers (in other words, there is no Layer 3 over vPC).• Do not use bridge assurance for interconnect vPC (DCI vPC) – use spanning-tree port type edge trunk• Use M1 ports for DCI vPC if flows between the 2 data centers need to be encrypted using 802.1ae MACsec



• Best Practices for Network Services / Appliances and vPC• Configure vPC to the inside and outside interfaces for ASA firewalls – use spanning-tree port type edge trunk• If needed, use multiple VRF instances for the inside interfaces – intra data center nets (see VMDC architecture)• Be aware of the following Layer 3 over vPC design caveat• Use dedicated Layer 2 port-channel for the service appliances state and keepalive VLANs (recommend don’t use

the vPC peer-link)• Recommended the ASA port channel hashing algorithm and the Nexus vPC hashing algorithm are the same• Connect ASA in routed mode to a vPC – must use static routing

• ASA static route to HSRP on Nexus• Nexus static route to ASA VIP

• If Connected ASA in routed mode and use dynamic routing • Single attach ASA to vPC domain• Create separate non-vPC interswitch link• Peer with non-vPC VLAN/SVIs

Firewall attached via vPC & Static Routes

Firewall attached via non-vPC Po & Dynamic

Routing

SLB attached via vPCSLB attached via Po

with orphan port suspend

Bandwidth reduced during certain failure scenarios

Bandwidth maintained

during certain failure scenarios



With NX-OS 6.1 and Prior Releases ::

• Always use identical line cards on either side of the vPC Peer Link and vPC member ports (legs to downstream device)

• The F1-series line cards can mix with M-series line cards• The F2-series line cards have to be in their own VDC; VDC type

[F2] meaning they can’t mix with F1 or the M-series in the same VDC

Interop F2 & F2E VDC

vPC ConfigurationMixed Chassis Mode :: Supported Topologies


Starting in NX-OS 6.2 and Later Releases ::

• VDC type [F2, F2E, F2 F2E] must match between the 2 vPC peer devices when F2 & F2E are used in same VDC; meaning its ok to have F2 on vPC peer device 1 and F2E on vPC peer device 2 for the vPC Peer Link or vPC member ports

• Note: in a F2 & F2E type of design; only features related to F2 apply (lowest common denominator)

• Always use identical line cards on either side of the vPC Peer Link and vPC member ports when M1, M1-XL, M2 & F2E in same VDC [M-F2E] or system

• When F2E is placed in a chassis with M-series it will operate in Layer 2 mode only leveraging the M for Layer 3 (proxy L3 forwarding)

vPC ConfigurationMixed Chassis Mode :: Supported Topologies


External (public)Nexus vPC best practices design guide http://www.cisco.com/en/US/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

Nexus 7000/6000/5000 Configuration Guideshttp://www.cisco.com/en/US/products/ps9402/products_installation_and_configuration_guides_list.htmlhttp://www.cisco.com/en/US/products/ps9670/products_installation_and_configuration_guides_list.html http://www.cisco.com/en/US/partner/products/ps12806/products_installation_and_configuration_guides_list.html

Nexus 5000 Enhanced vPC Configuration Guidehttp://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/mkt_ops_guides/513_n1_1/n5k_enhanced_vpc.html

vPC ConfigurationAdditional Resources & Further Reading

Great External Resource

http://www.cisco.com/en/US/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf



http://www.cisco.com/en/US/products/ps9402/products_installation_and_configuration_guides_list.html




http://www.cisco.com/en/US/partner/products/ps12806/products_installation_and_configuration_guides_list.html

http://www.cisco.com/en/US/partner/products/ps12806/products_installation_and_configuration_guides_list.html

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/mkt_ops_guides/513_n1_1/n5k_enhanced_vpc.html

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/mkt_ops_guides/513_n1_1/n5k_enhanced_vpc.html


Documents

Quick Start Guide Virtual Port Channel (vPC)