vPC design question - STP priority on non-vPC vlans and others

[Difan Zhao]

1. With peer-switch turned on, do I give same priority on non-vPC vlans like the vPC ones, or do I give lower value on the primary and higher on the secondary?

2. I will have a separate port-channel to carry non-vPC vlans. Can I use one vlan for L3 routing peering between the two Nexus?

Thanks,

Difan

[Difan Zhao]

Same:

Po900 is the inter-switch link that carries the non-vPC vlans. The E1/47 and 48 are the member ports in the Po900.

On the other switch, the spanning-tree status is forwarding

# sh vlan id 941

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
941  VLAN0941                         active    Po900, Eth1/47, Eth1/48

# sh spanning-tree vlan 941

VLAN0941
  Spanning tree enabled protocol rstp
  Root ID    Priority    941
             Address     0023.04ee.be28
             This bridge is the root
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    941    (priority 0 sys-id-ext 941)
             Address     0023.04ee.be28
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po900            Back BLK 1         128.4995 P2p

[rais]

Under non-VPC trunk do you have the following statement:

spanning-tree port type normal

[Difan Zhao]

Still the same...

The bridge assurance really just take care of the uni-directional problem. It won't make a difference in this case. You essentially look at connecting the two exactly same switches together who has the exact same bridge ID.

[rais]

Your logic is correct that if both bridges have same bridge-id this second link should be disabled. Isn't it RSTP per vlan?

I believe the solution is in presenting the same bridge-id for vPC domain/trunk vlans [e.g. using systgem-mac abcd.ef123.0001] and a different/actual bridge-id for non-VPC trunk vlans.

[Difan Zhao]

I agree but the system mac command will change the bridge ID for both vpc and non-vpc vlans. Another option is to disable peer-switch. However, in this case, switches will use their own system MAC as the bridge ID for both vpc and non-vpc vlans as well.

[shehab320]

yes, it should be blocked due to normal STP behavior

---

@Difan Zhao wrote:

Thanks for confirming. Even without the two green lines to your sw2, the link carrying the non-vPC vlans between the two switches is blocked on one side...

---