Layer 3 Etherchannel Confusion

[Ahmed Malik]

Hello,

       i have made a topology in packet tracer related to etherchannel configuration.

i am using 2 3560 switches and 1 2950 switch. Now what i want is to bundle up the redundant links between these 3 switches. The links fa0/1-3 between 2950_1 and 3560_1 switches have been bundled up but when i try to bundle the links fa0/4-6 of 3560_1 to fa0/4-6 of 3560_2 it wont work. i am using channel-group 1 mode desirable between the 3560 switches.

secondly if i want to assign ip to port channels then it has to be of same subnet between 2 3560 switches right and it must be same between 2950_1 and 3560_1. But these 2 subnets should be different from one another. right?

I am also attaching the pkt tracer file along with my question so help will be appreciated.

Regards,

Ali

[Giuseppe Larosa · Accepted solution]

Hello Ali,

I would like to note that C2950 is a L2 only switch, so in real world it is not suited for L3 etherchannels as it can have only one routed port alive in the whole box.

Try to see what happens when the first bundle between C2950 and C3560 is not configured.

You may be facing limitations of the emulation software.

Hope to help

Giuseppe

[Ahmed Malik]

So what it means is that etherchannel config should only be done between layer 3 switches and these switches are normally at the core layer.

Regards,

Ali

[glen.grant · Accepted solution]

  Between the 3560 and the 2950 you can only have a L2 or trunked etherchannel between the boxes.  Between the 3560's you should be able to create a L3 port channel or a layer 2 port channel .  Seeing you are negotiating the etherchannel the config parameters other than the address assigned to  the port channel SVI all other parameters must be exactly the same or it will not bring up the port channel . Usualy it will indicate in the logs why it wont build the port channel when it is negotiated.