UCS Upstream Port Channel Configuration

[Thiyagarajan K]

Hi Team,

I have a quick query on configuring the port-channel for UCS on Nexus 5K switches. I would like to know whether configuring the port-cahnnel connecting to UCS as "spanning-tree port type edge trunk"  will cause any impact to the STP running on UCS and is that a best practice to configure the UCS connected uplink as " spanning-tree edge trunk"

Ex:

interface Ethernet1/1

 description <<<conneted to F1-A>

  switchport mode trunk

  spanning-tree port type edge trunk

  channel-group 111 mode active

Regards,

Thiyagu

[d-fillmore]

Hi - Yes you should configure 'spanning-tree port-type edge trunk' on trunk ports connected to a UCS. You won't see any benefit from configuring it without the trunk keyword on a trunk port.

Whether it will cause any disruption to change it from 'spanning-tree port-type edge' to 'spanning-tree port-type edge trunk', I can't say for sure - If the ports are in a port channel and/or a vPC then you'll need to make the change on all ports at the same time, otherwise vPC will consider some of the member ports mismatched and there will be some disruption. I'd arrange some downtime to make the change

http://www.cisco.com/web/techdoc/dc/reference/cli/nxos/commands/l2/spanning-tree_port_type_edge.html

[Thiyagarajan K]

Thanks all for your support. Could you please help me to know how to find whether the UCS is running in a "endhost" mode or switching mode?

Regards,

Thiyagu

[Kirk J]

Unless you are running the UCSM in 'switch' mode for ethernet, which is not the default, it does not run spanning tree.  It uses other mechanisms such as designated receiver, deja vu checks, etc, for loop avoidance.  For a UCSM upstream switch port connectivity config only trunk (vs access) is supported, and you will want to have portfast/type edge spanning tree config so that the ports connected to the ucsm go immediately into forwarding and aren't impacted by spanning tree events.

I'm making the assumption you are referring to a UCSM domain with Fabric Interconnects.

Thanks,

Kirk...