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Community Member

2 single homed fabric extenders to the same Vpc with the same number

Hi there,

 

Is it a problem to give 2 single homed fabric extenders to the same Vpc domain the same fex & Portchannel numbers? (see the attached diagram)

 

The problem i'm having is when i move host ports from an old 6513 to the new fex'es it can take a very long time (5+  minutes) before i get connection to the server again

 

Just wondering if this could be the issue!

 

regards,

Pim

 

 

Everyone's tags (1)
1 ACCEPTED SOLUTION

Accepted Solutions
Bronze

It's confusing, but it's

It's confusing, but it's allowed.  As long as the FEX are port channeled locally only and not configured with VPC.  You can dual attach a device to both FEX and configure those ports for VPC.  Meaning, you can configure this:

interface port-channel 100
  switchport mode fex-fabric
  channel-group 100 mode active 

But you can NOT configure this (this requires the fex be dual attached):

interface port-channel 100
  switchport mode fex-fabric
  channel-group 100
  vpc 100

You can then connect a device (ie. server) to both FEX and configure this:

interface eth100/0/1
  switchport mode access
  switch access vlan 100
  channel-group 1001

interface port-channel 1001
 vpc 1001

The good thing about numbering both FEX with the same ID is that the N5K config will be identical if you dual attach a server via VPC.  But, it could be confusing that FEX 100 is actually two different devices.

3 REPLIES
Bronze

It's confusing, but it's

It's confusing, but it's allowed.  As long as the FEX are port channeled locally only and not configured with VPC.  You can dual attach a device to both FEX and configure those ports for VPC.  Meaning, you can configure this:

interface port-channel 100
  switchport mode fex-fabric
  channel-group 100 mode active 

But you can NOT configure this (this requires the fex be dual attached):

interface port-channel 100
  switchport mode fex-fabric
  channel-group 100
  vpc 100

You can then connect a device (ie. server) to both FEX and configure this:

interface eth100/0/1
  switchport mode access
  switch access vlan 100
  channel-group 1001

interface port-channel 1001
 vpc 1001

The good thing about numbering both FEX with the same ID is that the N5K config will be identical if you dual attach a server via VPC.  But, it could be confusing that FEX 100 is actually two different devices.

Community Member

Thanks danrya,Do you maybe

Thanks danrya,

Do you maybe have any insight on the problem i'm Having:

The problem i'm having is when i move host ports from an old 6513 to the new fex'es it can take a very long time (5+  minutes) before i get connection to the server again

I start Ping -T to the server I re-patch the cable to the Fex

Then it takes for ever before i get my ping back which should not be the case

 

regards,

 

Pim

 

Bronze

If the server port on the

If the server port on the 6513 is set as portfast (edge port), the MAC address table (CAM) of the upstream switch will not get flushed so your ping would continue going to the old 6500.  You could try doing a ping from the server side to refresh the MAC table quicker.
 

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