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adamgibs7
Frequent Contributor

Nexus Peer switch command

Dears,

as it is mentioned in the below link  that while entering the peer switch command it behaves like one switch by which command i can see the same bridge ID ???? as if now when i can see the show spanning-tree vlan X it shows me core2 as a root and core 1 as a primary, how i can justify to the client how the command is in effect.

This requirement comes from the origin of vPC peer-switch: both peer devices present themselved as a unique STP root device using the same bridge ID.

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

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Hi , 

Have a look on the below link for better clarification...

http://www.cisco.com/c/en/us/support/docs/routers/7000-series-routers/116140-config-nexus-peer-00.html

Hope it Helps..

-GI

View solution in original post

4 REPLIES 4

Dears,as it is mentioned in the below link  that while entering the peer switch command it behaves like one switch by which command i can see the same bridge ID ???? as if now when i can see the show spanning-tree vlan X it shows me core2 as a root and core 1 as a primary, how i can justify to the client how the command is in effect

Hi,

When you enable peer-switch command in Nexus, each single node nexus will share a virtual bridge ID  which allows both of them to act as root for the vlan.  For devices  with a connection to each N7k in the vPC domain that are not capable of  port-channel, L2 topology will rely on STP to block the redundant  links. 

The peer-switch feature allows for pseudo STP configurations to  allow non-vPC connections to load balance between the two N7k's.

The vPC peer-link will  always be in a forwarding status and it runs Layer 2 Gateway  Interconnection Protocol (L2GIP) to prevent bridging loops.  Each nexus  switch will send BPDUs with root bridge identified by virtual  bridge-ID. 

On vPC links, the designated bridge ID will also have the  virtual bridge-ID.  For non-vPC links, the designated bridge ID will be  the physical bridge-ID of the corresponding Nexus switch.

This allows  for the non-vPC switch (SW-1) to make a root decision based on the BPDU  advertisements instead of depending on port-priority to break the tie.  

Hope it Helps..

-GI

Dear 

The peer-switch feature allows for pseudo STP configurations to  allow non-vPC connections to load balance between the two N7k's

how ??

The vPC peer-link will  always be in a forwarding status and it runs Layer 2 Gateway  Interconnection Protocol (L2GIP) to prevent bridging loops.  Each nexus  switch will send BPDUs with root bridge identified by virtual  bridge-ID.

how i can see the virtual bridge id

Thanks

Hi , 

Have a look on the below link for better clarification...

http://www.cisco.com/c/en/us/support/docs/routers/7000-series-routers/116140-config-nexus-peer-00.html

Hope it Helps..

-GI

View solution in original post

thanks ganesh

very good doc