cancel
Showing results for 
Search instead for 
Did you mean: 
cancel

Taking links out of a port channel

TGF_Cisco
Beginner
Beginner

Hi

I am in the process of recovering some ports on my core switch connectin to the server farm switches.

gvadc-cr01#show int po1

Members in this channel: Gi1/0/5 Gi1/0/6 Gi2/0/5 Gi2/0/6

i want to remove 2 links out of the port channel to be used .

all the four links carry traffic and i want to make sure that there is no interruption to traffic .

I was planning to take the links out of the port channel first and then to shut down these links.

Is that correct?

1 ACCEPTED SOLUTION

Accepted Solutions

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Hello Eric,

You are generally correct here but note that the withdrawal of a link from a Port-channel will cause that its bandwidth and resulting STP cost will change, regardless of why the link was removed (either shutting it down or disconnecting it). The change to the STP cost may cause the STP to reconverge.

I therefore suggest configuring the STP cost on the Port-channel statically, using the spanning-tree cost command, before disconnecting the link. Use the same cost value the port currently has.

Best regards,

Peter

View solution in original post

7 REPLIES 7

Eric_Wu
Beginner
Beginner

I would actually do the opposite because once you take the port out of the port-Channel you create multiple connections to the same server. I would shut down the physical port first.

Sent from Cisco Technical Support iPhone App

thanks,, so  you mean to say the best approach would be to shut down the ports  as the initial step.

the  portchannel does not use LACP / PaGP. it is setup between two 3750 switches.

Eric_Wu
Beginner
Beginner

Oh sorry, I misread your original post. I thought it was a port channel to a server. If it is between switches then definitely shut down the port first before taking out of port channel. If you take it out of the port channel first you create another down link to the switch which will kick off spanning tree. Then it will take a few seconds to reconverge. By shutting down the link while in the port channel, you are just removing an additional link from the port-channel.

Sent from Cisco Technical Support iPhone App

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Hello Eric,

You are generally correct here but note that the withdrawal of a link from a Port-channel will cause that its bandwidth and resulting STP cost will change, regardless of why the link was removed (either shutting it down or disconnecting it). The change to the STP cost may cause the STP to reconverge.

I therefore suggest configuring the STP cost on the Port-channel statically, using the spanning-tree cost command, before disconnecting the link. Use the same cost value the port currently has.

Best regards,

Peter