Unanswered Question
Jan 27th, 2009


I have 4 switches - 2 in each datacentre. At the moment DataCentreA -Switch 1 - is plugged into - DataCentre B - Switch 1 and Datacentre A -Switch2 - is plugged into - DataCentre B Switch 2. Each is a seperate EPL with OSPF neighbor relationship running across each link. If both EPL's were plugged into the the 1 chassis at either DataCentre, I would use PortChannel but I don't know of a way of running PortChannel across 2 disparate switches in each data centre?

Any ideas?



I have this problem too.
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Jon Marshall Tue, 01/27/2009 - 05:22


You cannot create a port-channel from ports on different switches except for

1) 3750 switch stack

2) 6500 VSS solution

Is there is reason you need to run a portchannel ?


maryodriscoll Tue, 01/27/2009 - 05:28

Yes, there is....One of the physical epl's is very unstable and keeps dropping...OSPF will re-route but not quick enough for a heartbeat used between 2 X 3rd party telephony solutions. I am just searching all options before I go back to reducing OSPF hello/keepalive timers...



Joseph W. Doherty Tue, 01/27/2009 - 05:45

Then as Jon noted (and I forgot), VSS would be an option, although likely you'll need both supervisor (720C) and IOS upgrades. If you don't want to take that path, then you might consider if you could front the 6509s with a pair of 3750(-E)s. (It's also possible if you front 6509s, the stacked switches might be left as L2 devices - reducing IOS cost.)


Forgot to comment, reducing the OSPF hello timer on the links in question could be a viable solution. This might be the type of situation where subsecond OSPF hellos or BFD would be useful.


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