Do I configure spanning-tree port type ed trunk on LACP port-channels

[Paul Murray]

Hello,

Can't seem to see a clear answer and wondering if something could offer some advice please?

We are using LACP aggregation across all our 10 gig attached servers and also trunking them.  We're running a VPC pair of 5596 Nexus.

For a standard trunk port I always add the spanning-tree port type edge trunk to the interface config.

However I think I should be adding this to the overiding port-channel config.  At present a colleague has configured the VPC below omitting the spanning-tree port type config.

interface port-channel100

  description a-server

  switchport mode trunk

  switchport trunk allowed vlan 100

  vpc 100

The port member configs are these which do contain the spanning tree port type:

interface Ethernet1/1

  description a-server(1)

  switchport mode trunk

  switchport trunk allowed vlan 100

  spanning-tree port type edge trunk

  channel-group 100 mode active

I always try to keep the overiding port channel config the same as its members and obviously for most config, you can't have disparate configs anyway.

However for the spanning tree config the NexOS allows you to have the members with spanning tree port types and not have to reflect that in the port-channel.

However I have this issue with STP:

Switch1# show spanning-tree interface po100

Vlan             Role Sts Cost      Prio.Nbr Type

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

VLAN0100         Desg BKN*200       128.4996 (vPC) Network P2p *BA_Inc

Is this due to the inconsistency with my port channel to member configs?

Any advice would be gratefully accepted.

Thanks!

[Paul Murray]

Found the issue to be default spanning tree port types.  On this switch it's set to network whereas the default is edge on our base configs.

[Evren Sen]

Hi Paul, there are some parameters you can define on individual ports and there are some of them that will be inherited from the port-channel configuration no matter what has been configured under the infidividual ports. Spanning-tree configuration is one of the inherited ones. As soon as the port joins into a port-channel, it will start to use spanning-tree settings under the port-channel. When it leaves the channel, then it can continue to use the individual configuration.

There is a nice summary here under NX-OS Interface Conf Guide > Port-Channel Conf:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/6_x/nx-os/interfaces/configuration/guide/if_portchannel.html#wp1798338

Evren