Catalyst Switch Operation

  • Upload
    raj

  • View
    232

  • Download
    0

Embed Size (px)

Citation preview

  • 8/14/2019 Catalyst Switch Operation

    1/19

    1999, Cisco Systems, Inc. 6-1

    Chapter 6Catalyst Switch

    Operations

  • 8/14/2019 Catalyst Switch Operation

    2/19

    1999, Cisco Systems, Inc. www.cisco.com ICND6-2

    Address learning Forward/filter decision Loop avoidance

    Three Switch Functions

  • 8/14/2019 Catalyst Switch Operation

    3/19

    1999, Cisco Systems, Inc. www.cisco.com ICND6-3

    How Switches Learn HostLocations

    Initial MAC address table is empty

    MAC address table

    0260.8c01.1111

    0260.8c01.2222

    0260.8c01.3333

    0260.8c01.4444

    E0 E1

    E2 E3

    A B

    C D

  • 8/14/2019 Catalyst Switch Operation

    4/19

    1999, Cisco Systems, Inc. www.cisco.com ICND6-4

    How Switches Learn HostsLocations

    Station A sends a frame to Station C Switch caches station A MAC address to port E0 by learning

    the source address of data frames

    The frame from station A to station C is flooded out to allports except port E0 (unknown unicasts are flooded)

    MAC address table

    0260.8c01.1111

    0260.8c01.2222

    0260.8c01.3333

    0260.8c01.4444

    E0: 0260.8c01.1111

    E0 E1

    E2 E3DC

    BA

  • 8/14/2019 Catalyst Switch Operation

    5/19

    1999, Cisco Systems, Inc. www.cisco.com ICND6-5

    How Switches Learn HostLocations

    Station D sends a frame to station C Switch caches station D MAC address to port E3 by learning the

    source Address of data frames

    The frame from station D to station C is flooded out to all portsexcept port E3 (unknown unicasts are flooded)

    MAC address table

    0260.8c01.1111

    0260.8c01.2222

    0260.8c01.3333

    0260.8c01.4444

    E0: 0260.8c01.1111E3: 0260.8c01.4444

    E0 E1

    E2 E3 DC

    A B

  • 8/14/2019 Catalyst Switch Operation

    6/19

    1999, Cisco Systems, Inc. www.cisco.com ICND6-6

    How Switches Filter Frames

    Station A sends a frame to station C

    Destination is known, frame is not flooded

    E0: 0260.8c01.1111E2: 0260.8c01.2222E1: 0260.8c01.3333E3: 0260.8c01.4444

    0260.8c01.1111

    0260.8c01.2222

    0260.8c01.3333

    0260.8c01.4444

    E0 E1

    E2 E3

    XX

    DC

    A B

    MAC address table

  • 8/14/2019 Catalyst Switch Operation

    7/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-7

    Broadcast and Multicast Frames

    Station D sends a broadcast or multicast frame

    Broadcast and multicast frames are flooded toall ports other than the originating port

    0260.8c01.1111

    0260.8c01.2222

    0260.8c01.3333

    0260.8c01.4444

    E0 E1

    E2 E3 DC

    A B

    E0: 0260.8c01.1111E2: 0260.8c01.2222E1: 0260.8c01.3333E3: 0260.8c01.4444

    MAC address table

  • 8/14/2019 Catalyst Switch Operation

    8/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-8

    Broadcast Storms

    Segment 1

    Segment 2

    Server/host X Router Y

    Broadcast

    Switch A Switch B

    Host X sends a Broadcast

  • 8/14/2019 Catalyst Switch Operation

    9/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-9

    Broadcast Storms

    Segment 1

    Segment 2

    Server/host X Router Y

    Broadcast

    Switch A Switch B

    Host X sends a Broadcast

  • 8/14/2019 Catalyst Switch Operation

    10/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-10

    Broadcast Storms

    Segment 1

    Segment 2

    Server/host XRouter Y

    Broadcast

    Switches continue to propagate broadcast traffic overand over

    Switch A Switch B

  • 8/14/2019 Catalyst Switch Operation

    11/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-11

    Multiple Frame Copies

    Segment 1

    Segment 2

    Server/host X Router YUnicast

    Switch A Switch B

    Host X sends an unicast frame to router Y Router Y MAC address has not been learned by either

    switch yet

  • 8/14/2019 Catalyst Switch Operation

    12/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-12

    Solution: Spanning-Tree Protocol

    Provides a loop free redundant network topology byplacing certain ports in the blocking state

    Blockx

  • 8/14/2019 Catalyst Switch Operation

    13/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-13

    Spanning-Tree Operations

    One root bridge per network One root port per nonroot bridge One designated port per segment

    x

    Designated port (F) Root port (F)

    Designated port (F) Nondesignated port (B)

    Root bridge Nonroot bridgeSW X SW Y

    100baseT

    10baseT

  • 8/14/2019 Catalyst Switch Operation

    14/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-14

    Switch YDefault priority 32768(8000 hex)MAC 0c0022222222

    Switch XDefault priority 32768(8000 hex)MAC 0c0011111111

    Spanning-Tree ProtocolRoot Bridge Selection

    BPDU

    BPDU = Bridge protocol data unit(default = sent every 2 seconds)

    Root bridge = Bridge with the lowest bridge IDBridge ID = Bridge priority + bridge MAC addressIn the example, which switch has the lowest bridge ID?

  • 8/14/2019 Catalyst Switch Operation

    15/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-15

    Switch YDefault priority 32768MAC 0c0022222222

    Switch XDefault priority 32768MAC 0c0011111111

    Spanning-Tree ProtocolPort States

    Root bridge

    x

    Port 0

    Port 1

    Port 0

    Port 1

    100baseT

    10baseT

    Designated port (F) Root port (F)

    Nondesignated port (B)Designated port (F)

  • 8/14/2019 Catalyst Switch Operation

    16/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-16

    Spanning-Tree ProtocolPath Cost

    Link Speed Cost (reratify IEEE spec) Cost (previous IEEE spec)----------------------------------------------------------------------------------------------------

    10 Gbps 2 11 Gbps 4 1100 Mbps 19 1010 Mbps 100 100

  • 8/14/2019 Catalyst Switch Operation

    17/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-17

    Switch YMAC 0c0022222222Default priority 32768

    Switch XMAC 0c0011111111Default priority 32768

    Port 0

    Port 1

    Port 0

    Port 1

    Switch ZMac 0c0011110000Default priority 32768

    Port 0

    Can you figure out: What is the root bridge? What are the designated, nondesignated, and root parts? Which are the forwarding and blocking ports?

    100baseT

    100baseT

    Spanning-Tree:

  • 8/14/2019 Catalyst Switch Operation

    18/19 1999, Cisco Systems, Inc. www.cisco.com ICND6-18

    Switch YMAC 0c0022222222Default priority 32768

    Switch XMAC 0c0011111111Default priority 32768

    Port 0

    Port 1

    Port 0

    Port 1

    Switch ZMac 0c0011110000Default priority 32768

    Port 0

    Can you figure out: What is the root bridge? What are the designated, nondesignated, and root parts? Which are the forwarding and blocking ports?

    100baseT

    100baseT

    Spanning-Tree:

    Designated port (F)

    Root port (F)

    Nondesignated port (BLK)Designated port (F)

    Root port (F)

  • 8/14/2019 Catalyst Switch Operation

    19/19

    Blocking

    Listening

    Learning

    Forwarding

    Spanning-Tree Port States

    Spanning-tree transitions each portthrough several different state: