Port channels on a fex interface

[ryancisco01]

Hi,

we have cisco 5k's with fex's attached:

N5k1 -> fex101

->

-vpc peer link-

->

N5k2 -> fex 102

What I have now done is tried to configure a vpc off the two fex's toward a server, the interfaces are up but the port channel refuses to come up, just wondering, is this config supported since a vpc has to be defined from the nexus to the fex? essentially its a new vpc inside another vpc? It took the commands without any complaints.

Currently shows:

port-channel50 is down (No operational members) vPC Status: Down, vPC number: 50 [packets forwarded via vPC peer-link]

[balaji.bandi]

First question is the FEX are Dual Homed ? (this means FEX 101 connected to Nexus 5K 1 and 5K2) if not that not going to work.

post the config.

or here is example you need to seup for the Server to use port-channel.

Nexus 5K1 and 52 config :

!
fex 101
pinning max-links 1
description "XXXXXXXXXX"
!
slot 101
provision model N2K-C2248TP-E-1GE
!
fex 102
pinning max-links 1
description "XXXXXXXXXX"
!
slot 102
provision model N2K-C2248TP-E-1GE
!
!
interface Ethernet1/YY
description *** Uplink1 : FEX 101 ***
switchport mode fex-fabric
fex associate 101
channel-group 101
!
interface port-channel101
switchport mode fex-fabric
fex associate 101
vpc 101
!
interface Ethernet1/XX
description *** Uplink1 : FEX 102 ***
switchport mode fex-fabric
fex associate 102
channel-group 102
!
interface port-channel102
switchport mode fex-fabric
fex associate 102
vpc 102

This config for server
=========================================================

interface Ethernet 101/1/1
no cdp enable
switchport access vlan XXXX
spanning-tree port type edge
channel-group 14 mode active
!
interface Ethernet 102/1/1
no cdp enable
switchport access vlan XXXX
spanning-tree port type edge
channel-group 14 mode active
!
interface port-channel14
no lacp suspend-individual
switchport access vlan XXX
spanning-tree guard root
!

[ryancisco01]

Hi thanks for the reply,

no the fex's are single homed, fex101 connects to N5k1 only and fex102 connects only to Nk52

The rest of the config I am using matches the config you have provided above. 

Can you advise if there is any document that shows this limitation? I have just found a document which seems to indicate this is supported - 

https://www.cisco.com/c/en/us/support/docs/switches/nexus-2000-series-fabric-extenders/200363-nexus-2000-fabric-extenders-supported-un.html#anc7

Is there a s/w limitation perhaps? I am currently on 6.0(2)N2(5)

[Reza Sharifi]

If each FEX is attached to only one switch, you don't need any vPC.

You only need a Portchannel on the switch and the server-side configured with mode "on or LACP".

The other option would be to simply connect the server to 2 FEXs using a trunk or access port (no portchannel) and configure the server-side with high availability.

HTH

[ryancisco01]

I have tried Po50 with and without vPC config on both nexus, both times it refuses to come up same error - no operational members

The link from the nexus to the fex:

interface port-channel101
description To FEX
switchport mode fex-fabric
fex associate 101

link between the nexus':

interface port-channel1
switchport mode trunk
vpc 1

Link to the server:

interface port-channel50
no lacp suspend-individual
no lacp graceful-convergence
switchport access vlan 1
vpc 50

interface Ethernet101/1/2
switchport access vlan 1
channel-group 50 mode active

(The config is replicated on nexus 2)

Any other reason this might not be working?

[Reza Sharifi]

The link between Nexus is missing this command:

vpc peer-link

HTH

[ryancisco01]

good spotting, unfortunately that was my mistake, po1 is the non vpc trunk and po14 is the vpc peer:

interface port-channel14
switchport mode trunk
spanning-tree port type network
vpc peer-link

also to add context, I have several vpcs working fine where the links are physically attached to the 5k, none work on the fex.

I have noticed one command missing which I saw in one example online, the port channel to the fex does not have a vpc specified, is that required? I have other active ports on the fex so bit hesitant to just try and put it on

eg should it be:

interface port-channel101
description To FEX
switchport mode fex-fabric
fex associate 101

vpc 101

[Reza Sharifi]

I have noticed one command missing which I saw in one example online, the port channel to the fex does not have a vpc specified, is that required?

No, if each fex is connected to only one parent switch, there is no need for that command (vpc xx).

HTH

[balaji.bandi]

If the FEX not dual homed your confiiguration seems to be ok.

in regards to port-channel to server, is the server card support LACP ? if not as suggested go with access port, if one fails other one able to take over load - based on windows server config.

[pman]

Hi,

Attaches a configuration to your situation:

http://vpackets.net/2014/10/vpc-order-of-operations/

[ryancisco01]

thank you that confirms at least what we are doing should work.

we have the team checking the server for any issues now. They definitely support lacp, we will attempt to bring them up as individual links now to determine where the issues lays.