4500-x vss MEC to 2960-x stack

[awcrane]

                  Building A

(2) 4500-x VSS

(9) closets with 2960-x stacks

(2) Data Center N5K-C5596t

I'm having a difficult time trying to find documentation.

I have the (2) 4500-x configured with VSS and am trying to find info on connecting the 2960-x stacks.

[Reza Sharifi]

Hi,

There is nothing special about the connections.  Take 2 connections or more from each stack and connect them to both 4500 (one to each 4500) and put them in a portchannel.  It is just as any other portchannel except this time you are connecting a stack to a pair of VSS switches.

HTH

[awcrane]

command rejected by the 2960-x stack

%With PAgP enabled, all ports in the Channel should belong to the same switch

Command rejected (Port-channel20, Te3/0/1): Invalid etherchnl mode

%With PAgP enabled, all ports in the Channel should belong to the same switch

Command rejected (Port-channel20, Te3/0/1): Invalid etherchnl mode

[Reza Sharifi]

Use LACP with 4500 as active and 2960 as passive

[awcrane]

I have all the closet stacks up using LACP. I'm trying to configure Dual-
Active detection. I think from what I have read I should be able to use fast hello on a dedicated link but it won't accept the commands. I believe the BRAND NEW 4500-x switches may need a NEWER IOS to support fast hello. They were recieved running (cat4500e-UNIVERSALK9-M), Version 03.04.02.SG RELEASE SOFTWARE (fc1).

[Jami Bailey]

You can use PAgP only in single-switch EtherChannel configurations; PAgP cannot be enabled on cross-stack EtherChannels. As Reza mentioned, you can use LACP or mode On.

channel-group X mode active|passive|on

[awcrane]

ok. I'll give that a try. I thought I had read somewhere that it worked with epagp.

[Reza Sharifi]

No, MEC works with LACP.

[Pierluigi Torriani]

Hi i agree with Reza, epagp works only if 2960x aren't  in stack.

[MARVIN SPITERI]

Hi

yes I think cisco is only giving info about ePAGP to use for MEC with VSS. But for instance my scenario is 2 x 4500-x switches with vss and distribution with a stack of 2 x 3750-x switches and I tried to research about how best to configure MEC. I also have access 2960-x switches with etherchannels to the core. My plan is to use LACP with active active as this is the only option I see. The 4500-x will have 4 x 10 G DAC cables between them for the VSL and use LACP on mode.

So the LACP from any other switches to the VSS core seems not to need any other config apart from the 'active' mode right?

So the VSS will just 'use' such LACP links to pass MEC related checks and then if the VSL link splits it will shutdown all interfaces on the standby VSS switch correct?

Anyone has any ideas for a better option/s ?

[awcrane]

ok.Everything I have been reading about configuring Cisco VSS Dual-Active Detection kept talking about using Epagp. and I thought i read the 2960-x supported it. So I guess the deal breaker is I'm stacking the 2960-x switches.

[Pierluigi Torriani]

Hi,

some info.

PAgP is supported in all platforms except the Cisco Catalyst 37xx stack configuration in which cross-stack EtherChannel (LACP) is required to have MEC-connectivity with the VSS. Because cross-stack EtherChannel does not support PAgP, it cannot use enhanced PAgP for dual-active detection. A common approach to resolve this gap in support is to use two EtherChannel links from the same stack member. This solution is a non-optimal design choice because it creates a single point-of-failure. If a stack member containing that EtherChannel fails, the whole connectivity from the stack fails. To resolve this single point-of-failure problem, you can put two dual-link EtherChannel group, each on separate stack member connected to VSS; however, it will create a looped topology. The loop-free topology requires a single EtherChannel bundle to be diversified over multiple members which in turn requires LACP.

[Rodrigo Ferroni]

Hi,

I was wondering if I can connect 6500 in vss mode with 4500-x en vss mode also (two differents data centers) using just portchannel. I think so, but I can't find out where to confirm.

Sorry If I made a silly question! 

Thanks in advance.

/rodrigo