Connecting Switches over EoSDH WAN for multicast

Unanswered Question
Sep 16th, 2009


I'm looking for some tips / advice on the best way to connect up two switches which will be connected over a WAN link via a 100Mbps EoSDH leased line.

The provider will be COLT using their lanlink technology.

The switch's on either end of the connection would be either CISCO 3750's or 4948's. Multicast will be running over the link.

The simplest method I thought would be to have the ports configured with a basic 'switchport mode access', but would it be recommended to rather trunk the connection?

I have no need to pass over multiple VLAN's, but simply to receive the multicast traffic already available in a VLAN on the remote end.

Thanks in advance for any tips.


I have this problem too.
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Edison Ortiz Thu, 09/17/2009 - 06:08

If you don't need to pass multiple Vlans over this connection, then you don't need to configure a trunk. An access vlan configuration should work.

This connection will be seen as connecting 2 switches back-to-back, the provider is transparent on any configuration design you may have.



Paolo Bevilacqua Thu, 09/17/2009 - 06:53

I would personally set port to trunk every time a switch is connected to another.

Yes I'm conservative :)

mariov652 Fri, 09/18/2009 - 04:36

Thank you for both tips.

I understand that trunking may the the *correct* way to connect these, but for various reasons, I'd like the port on the A-End to simply be seen as another 'PC' or 'Server' attached to the remote switch.

The idea is to have mulitcast receivers on the B-End sitting in the same VLAN as the WAN connection and simply make multicast requests to the IGMP broadcasts to subscribe to the feed.

Can you confirm if a:

"switchport mode access",

"Switchport access vlan X",

"multicast-routing", and

"ip pim sparse-mode" on the WAN port interfaces is all that is needed to enable the connection?

Am I simplifying things too much that I am not seeing I may run into problems later?

Would trunking be a better solution for this and why?

Thanks again,

Edison Ortiz Fri, 09/18/2009 - 05:06

The commands you illustrated are the ones you need. You also need the RP information at both end as you are using 'sparse-mode'.




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