VPC Peer Link

[kesva.naidoo]

What is the function of the VPC peer-link? Should be the composite of all VPC links that are dual homed between switches?

In this diagram, is it necessary to have 8 x 10G links as shown above. The links conecting the 7Ks to the 5Ks are VPC links.

[Reza Sharifi]

vPC Peer Link

The peer-link PortChannel connects vPC peers and carries all access VLANs (defined by the user). This link also carries additional traffic that the user does not need to define: more specifically, BPDUs and HSRP hellos and MAC address synchronization between the vPC peers.

This link is by far the most important component of the vPC system. Although its failure does not disrupt existing vPC flows, its failure can impair the establishment of new flows and isolate orphan ports. Configuring the peer link in a redundant fashion helps ensure essentially uninterrupted connectivity between the vPC peers

for more info refer to this link:

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9670/C07-572835-00_NX-OS_vPC_DG.pdf

The vPC peer link is usually 2 10Gig interfaces and the vPC peer keepalive is a Gig interface (routed) using the mgmt0 on the sup module.

HTH

[kevinzhang]

Do I need vlan pruning on this link?

Sent from Cisco Technical Support iPad App

[Reza Sharifi]

The vPC peer link is usually 2 10Gig interfaces and the vPC peer  keepalive is a Gig interface (routed) using the mgmt0 on the sup module.

You don't need vlan punning.  Just allow the specific vlans you need to have on the link.

HTH

[John Peterson]

Hi Reza,

Digging up a old thread here...

We have a number of VLANs which will be used by virtual port-channels for hosts connected to 2200 fexs. We also have VLANs which are not required by hosts connected to the Nexus 2K. 

I understand all VLANs which are used by the hosts connected to the 2K (vPC) are required to be trunked on the peer link. 

My confusions steam when we have VLANs which are not trunked towards to N2K, should we have another normal trunk link in addition to the peer link or is the Nexus 5K clever enough to understand which VLANs should be forwarding on the peer link?

Thanks. 

[Alexander Cousins]

If the hosts on the ports that are not trunked off a FEX need to communicate with hosts on a FEX or vPC connection then yes i believe you need those VLANS on the Peer link as well. Only if you have isolated VLANS between would you go down the additional trunk route.

[John Peterson]

ok, so as I read your reply I would like to confirm the following:

• Hosts which are not connected to the FEX via normally trunk or vPC which need to communicate to Hosts which are on a vPC these VLANs need to be trunked on the vPC peer link.
• VLANs which communicate between devices which are not on the vPC is recommended to have a seperate link. 

I now have an issue, where I have a Nexus 1000v deployed in vmware which we are using L3. The control (same requirements for vMotion VLAN) VLANs requires to be L2 and is trunked via the physical uplinks which also carry VLANs which have HSRP on the 5Ks. 

As a port-channel from each hosts will terminate on each fex as part of a vPC, each will be carrying VLANs which only require L2 communication and some which have a gateway (HSRP).

For VLANs which carry only L2 information i.e. Control VLAN or vMotion VLAN, they are required to communicate with other hosts at this point if source packet arrives one Fex 1 which is connected to N5K1 and required to communicate to destination on Fex 2 which is linked to N5K2 it would need to transit via the two Nexus 5Ks, could this be achieved by the peer link or would I need a separate link carrying these VLANs in addition to them being carried over the vPC peer link?

[Alexander Cousins]

Hi JohnPete

Have you considered VM-FEX as an alternative to the 1000v? They are both based on the same technologies but the architecture of VM-FEX is such that it replicates the operation and configuration of a FEX module and more importantly is aligned with the architecture of  vPC.

HTH

[John Peterson]

Hi Lex,

I'm afraid we already have the N1K implemented.

Were you able to advise on the comments above?

Thanks

[Alexander Cousins]

In that case the diagram at the top would really help as it does not appear to be working. Are you able to update the diagram?