Nexus 5k with dual-homed FEX 2k

[dastechnologies]

Hello everyone.

I have a strange behaviour in diagnostic messages.

I configured two Nexus 5k and different Fex in dual-homed like in this figure:

 

All is working well.

But if I try to check vpc status there are strange results.

#show vpc brief

vPC domain id : 1
Peer status : peer adjacency formed ok
vPC keep-alive status : peer is alive
Configuration consistency status : success
Per-vlan consistency status : success
Type-2 consistency status : success
vPC role : primary
Number of vPCs configured : 169
Peer Gateway : Enabled
Peer gateway excluded VLANs : -
Dual-active excluded VLANs : -
Graceful Consistency Check : Enabled
Auto-recovery status : Enabled (timeout = 240 seconds)

vPC Peer-link status
---------------------------------------------------------------------
id Port Status Active vlans
-- ---- ------ --------------------------------------------------
1 Po512 up 1,434,437,439,441

vPC status
----------------------------------------------------------------------------
id Port Status Consistency Reason Active vlans
------ ----------- ------ ----------- -------------------------- -----------
101 Po101 up success success -
102 Po102 up success success -

But if i try to check port channel 101 and 102 I see this:

#show int po101

port-channel101 is up

vPC Status: Down, vPC number: 101 [packets forwarded via vPC peer-link]

All is working well (I view all FEX connected and traffic has no problem wiht different portchannels), but I don't understand why vpc status id down.

The same message is in both switches.

Do you have any experience with this issue?

Nexus platforms:  Nexus 5672

FEX:  N2K-C2232TM-E-10GE

System version: 7.1(0)N1(1b)

Thank you for your help!

[Reza Sharifi]

Hi,

It maybe that you don't have the same config on both switch 1 and 2 for po101.

Can you post configs from both switches?

HTH

[dastechnologies]

Thank you for the reply,

I checked the conf, in the case of different configurations, the consistency check would be failed.

I post extracts of the two configs.

[Reza Sharifi · Accepted solution]

Thanks for posting the config.

You are correct. They are exactly the same.

Is it the same for po102 or just 101?

[dastechnologies]

I have 5 fex configured, 

all are working with the same configuration,

and all the fex show vpc up in show vpc command,

but vpc down in show int po101,102, ecc...

I didn't notice any malfunctioning,

but I don't understand why the show int po show vpc status down.

[dastechnologies]

Anyway,

the configuration is the same for all the po.

I copied it from another data center, where there is no strange behaviour.

Tomorrow I'll try to reboot the switch, but maybe it could be a software bug.

[dastechnologies]

After reboot nothing change, and no disrupting noticed.

The next step will be to upgrade OS

[Jigar Dave]

Hi Das Technologies,

Do not attempt to reboot right now. Please do following configuration, this is right approach to configure FEX which is connecting to Nexus.

#create FEX on Nexus switch

conf t

fex 111

  pinning max-links 1

  description "FEX 101"

#create port-channel

interface port-channel111

  description ** PO111 (Eth2/11,12) to FEX111 (RACK Location) **

  switchport mode fex-fabric

  fex associate 111

Go to interface:

interface Ethernet2/11

  description ** To FEX111  - PO111 **

  switchport mode fex-fabric

  fex associate 111

  channel-group 111

Please replicate this in your environment based on Twinax or Fiber you have connected between FEX and NEXUS.

from your design, it looks like you have 2x10G going from FEX to each NEXUS.

Please share the results.

[dastechnologies]

Dear Dave,

thank you for the reply.

In your suggestion I wonder why you didn't insert a vpc for the port-channel?

I configured the two Nexus in this way:

fex 101
    pinning max-links 1
    description "FEX-01"

interface port-channel101

description FEX-01
switchport mode fex-fabric
fex associate 101
vpc 101

interface Ethernet1/1
    description FEX-01-PORT-1
    switchport mode fex-fabric
    fex associate 101
    channel-group 101

interface Ethernet1/2
    description FEX-01-PORT-3
    switchport mode fex-fabric
    fex associate 101
    channel-group 101

Kind regards.

[dastechnologies]

All solved after upgrade to reccomended version 7.1(4)N1(1)