Ether Channel between 3750x and 2950

Debudas123 · ‎03-04-2013

I have a one 3750x switch and 10 nos of 2950 switch, i want to configuration etherchanel between 3750 to 2950, for that i need 10 nos of etherchanel interface(virtual), but the 2950 switch support maximum of 6 nos of etherchanel port, so is there any option to solve it?

Regards

Debabrata

Peter Paluch · ‎03-05-2013

Hello,

I am not sure if I understand your concern. On each 2950, only a single EtherChannel instance will be needed as you will be creating only one EtherChannel towards the 3750. Hence, the limitation of maximum of 6 EtherChannel instances on an 2950 switch should not really be any limitation in your case.

I am not sure if this answers your question so please feel welcome to ask further!

Best regards,

Peter

Debudas123 · ‎03-05-2013

Hello,

but i have to mentioned the etherchanel ID nos. within the rages of 1 - 6,

so i have configured etherchanel only 6 switches with different IDs, if I configure the same ID in this topology then it will be overlap.....

Thanks

Debabrata

Peter Paluch · ‎03-05-2013

Hello Debabrata,

so i have configured etherchanel only 6 switches with different IDs, if I  configure the same ID in this topology then it will be overlap.....

EtherChannel numbers between different switches do not have to be identical. You can safely connect two switches with an EtherChannel that has Port-channel1 on one switch and Port-channel9 on the other, for example. The numbers of Port-channel interfaces are local to the switch and they are never sent nor compared between switches.

Do not worry. Simply configure all 2950 with Port-channel1 and on 3750, create Port-channelN with N being 1,2,3,... as necessary.

Best regards,

Peter

Debudas123 · ‎03-08-2013

Okay.. if i configure the switches like this --

3750 2960

switch port 0/1--------------------------------------------------------------------> switch port 0/1

channel-group 1 mode on channel-group 5 mode on

switch port 0/2--------------------------------------------------------------------> switch port 0/2

channel-group 1 mode on channel-group 5 mode on

then i will connect 0/1 of 3750 (channel-group1) to 0/1 of 2960 (channel-group 5) and 0/2 of 3750 (channel-group 1) to 0/2 of 2960 (channel-group 5)..

then it will work ?

Thanks

Debabrata

Peter Paluch · ‎03-08-2013

Hello Debabrata,

then i will connect 0/1 of 3750 (channel-group1)  to 0/1 of 2960  (channel-group 5) and 0/2 of 3750 (channel-group 1) to 0/2 of 2960  (channel-group 5)..
then it will work ?

Yes, it will work perfectly. As I explained earlier, the number of the channel-group is local to the switch where it configured. This number does not have to match between two different switches.

One more comment. I see you are creating the EtherChannel using mode on. I strongly discourage you from doing that. This configuration forces the ports to be bundled in an EtherChannel regardless of the state on the opposite device. This can lead to switching loops if the ports are not bundled on the opposite device, or if they are accidentally connected to different devices. To prevent these problems from occuring, you should absolutely use a negotiation protocol that allows the switches to negotiate whether the ports shall be bundled, and will start using them as a single EtherChannel bundle only if both switches agree to do so. There are two signalling protocols you can use - PAgP and LACP, LACP being preferred because it is open and widely supported. So instead of using mode on, use the following configuration

interface range fastethernet0/1 - 2

channel-group 1 mode active

The mode active activates the LACP and requires the device to actively negotiate the creation of the EtherChannel with the opposite device.

Best regards,

Peter

Debudas123 · ‎03-08-2013

Okay

thanks

Let me check...

Reagrds

Debabrata

Steve Fuller · ‎03-09-2013

Just to add to Peter's comment regarding the use of a negotiation protocol on the port-channel, some platforms and versions of Cisco IOS may default to Cisco PAgP so if you want to use the standards based LACP you will also need to add the command channel-protocol lacp to each physical interface.

Regards

Peter Paluch · ‎03-09-2013

Hello Steve,

Thanks for joining!

Are you absolutely sure about the channel-protocol command? Please note that in the channel-group command, the keywords active/passive unambiguously refer to LACP while keywords desirable/auto refer unambiguously to PAgP. Hence, by choosing any of these keywords, you automatically and unambiguously also select the signalling protocol. Hence, the purpose of channel-protocol is largely cosmetical - to prevent you from activating a different signalling protocol should you have troubles remembering which keywords relate to which signalling protocol (and yes, they are strongly unintuitive).

See the following threads where I discussed this fact in more detail:

https://supportforums.cisco.com/message/3233198#3233198

https://supportforums.cisco.com/message/3583209#3583209

Best regards,

Peter

Steve Fuller · ‎03-09-2013

Hi Peter,

Having looked at this again, and you're other posts on the subject, I think you're correct that largely cosmetic. In the usage guidelines section of the channel-protocol command in the Catalyst 6500 Command Reference it makes the following statements which hint at what you've said:

You can also select the protocol using the channel-group command.

[..]

You can use the channel-protocol command to restrict anyone from selecting a mode that is not applicable to the selected protocol.

Thanks for the pointer.

Regards