Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Forwarding Multicast over WAN


The task is to design an architecture that distributes multicast traffic from location B to C. Location B currently subscribes and receives multicast traffic from location A.

Distance between B and C is around 290 miles (470 km).

The WAN service between B and C would be provided via GRE-Tunnel.

How easy/difficult is it to have the multicast traffic from location A subscribed to from location C or alternatively forwarded from location B to location C (If possible)?

Our thinking is simply to have a Layer 2/3 device acting as switch and router with PIM enabled on each interface.

Our other thinking is to have a VLAN-to-VLAN type connection between location B and C. Then all the PIM is handled by the interfaces at location B.

Is there a specific technical term for this type of connection?

Is this possible utilizing the GRE-Tunnel mentioned above or do we request another form of 'Tunnel'/Connection?

Thanks for any advice.


Hall of Fame Super Gold

Re: Forwarding Multicast over WAN


If your SP can provide a service carrying multicast, like tagged ethernet transport, and you're confident in their level of services, I would recommend using it.

On the other hand, doing mcast over gre is routinely done and works well.

In both cases you configure a simple PIM network and should have no issues.

If you never did mcast before, recommend reading the white papers:

New Member

Re: Forwarding Multicast over WAN


I am pretty confident in the service that can be offered, but am not completely up-to-date with the terminology regarding WAN links.

Is the 'Tagged Ethernet Transport' you mention a VLAN-to-VLAN type of connection?

My concern regarding GRE is that I understand this traffic is handled in software rather than hardware (at least in terms of the CISCO 49xx series) and I'd like to avoid this overhead.

I've seen it done in other offices, but I was thinking a link between the two sites whereby switches on either side have an 'uplink' to eachother sharing VLAN information would be easiest and most efficent way to send multicast over distance.

- I'm unsure of the term used for this kind of link though.

I have worked with multicast, but I need to understand the various ways this connection can be achieved and select the most apprropriate for us. Compare every possible architecture and likely outcome before selecting an architecure type.


Hall of Fame Super Gold

Re: Forwarding Multicast over WAN


your considerations are mostly correct. If you can have transparent ethernet support, use it. It doesn't even necessarily be of the VLAN (tagged) type, actually I would recommend avoiding VLANs spanning remote locations.