Port-channel config issue

[Bob Greer]

Hi there,

Thanks for reading.

I'm finding a physical inf in UP/DOWN (Suspended) state.  Investigation shows a problem with our initial configuration and a clear fix: set 1/0/6 mode:trunk.

interface GigabitEthernet1/0/5
 description swuk602-po2
 switchport mode trunk
 channel-group 2 mode active
!
interface GigabitEthernet1/0/6
 description swuk602-po2
 channel-group 2 mode active

My question is: what happens to the port channel when I fix the 1/0/6 mode?  Right now, the other inf is carrying the Po which shows up/up (connected).  Will I bounce the Po if I change properties of 1/0/6?  Is it a single ping lost or down for 15-20 seconds or so?

Thanks!

Bob

[acampbell · Accepted solution]

Bob,

In my opinion...

You are basically adding a channel into the port-channel.
There should be no adverse affect on existing traffic.

The switch will build up it data table for load sharing across the port-channel
and packet will be sent on the interface selcting from the channelling HASH mechanism.

It is more likely you would drop a ping or 2 when an interface is lost and an existing
IP or MAC stream has to re-route.

May be this link will help:-
http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html

Regards
Alex

[Bob Greer]

Hi guys,

Thanks for replying!

I sourced a couple of 3750s after PacketTracer failed to accurately represent the layout (the phy inf stayed up/up after moving from trunk to access).

I found I was able to move a member of the port channel in and out of the group (trunk->access->trunk) without the port channel inf resetting.  Consistent with gpauwen's findings, the physical interface took about 15-20 seconds to negotiate and change to up/up but the Port Channel logged no losses.

Thanks again!

[Georg Pauwen]

Hello,

I labbed this in GNS, and both removing and adding a port to the channel led to a 30 second timeout on the connection between end hosts on either side of the channel. This is (I think) due to STP coonvergence.