Routing configuration to forward multicast traffic to a tunnel interface

Hi all,

I have a L3 network topology where the core network segment doesn't support IP Multicast protocols.

As such, I have configured a couple of X460 switches/routers in order to provide an end-to-end GRE tunnel able to encapsulate Multicast traffic without the need for IGMP/PIM (no control on the core network routers).

I expected to force Multicast traffic to be routed through the GRE tunnel interface by configuring a route in a similar way I'm used to do with Linux, e.g.:

add route -net netmask dev my_tunnel_gre

Unfortunately, I haven't found a command in the manual to configure such a route on ExtremeOS.

Does anyone have any idea how to achieve such a behavior?

I appreciate any answers able to solve the above issue.

Thank you.



5 replies

Userlevel 5
Hi Luca, I don't think EXOS allows you to specify a Class D address in a route. I'll need to verify that. However, you can add a multicast route to the routing table using the following command:
configure iproute add [u] multicast
configure iproute add multicast[/code]This tells the router to forward all mutlicast streams originating from the subnet via the interface, which would be the destination address of your GRE tunnel. And because, this is a static route, it will have precedence over any dynamic routes that may exist to the same destination.

I hope this is what you're looking to implement

you're right, Class D addresses are not allowed by EXOS.

The Multicast route you suggested seems to satisfy my request.

Is there a way to apply it to separate Multicast streams (e.g., in order to allow, for instance, data traffic instead of routing control plane information through the GRE tunnel?

Thank you very much for your precious help.


I tried the above configuration.

If I correctly understood the behavior of the Multicast route, supposing of having the subnet configured to belong to an OSPF Area, I would be able of forwarding OSPF Hello messages addressing the IP Multicast address "" on the other side of the tunnel.

Strangely, this doesn't seem to happen as the OSPF router at either side of the tunnel does not see any neighbor.

How come?

Where are my assumptions wrong?

Thank you.

Userlevel 4
I don't think the current EXOS implementation supports mulitcast forwarding over GRE tunnel.

• IPv4 only (both the routed traffic, and tunnel protocol)
• Unicast forwarding only, no Multicast
• Single IP address can be configured on a GRE tunnel
• Duplicate Address Detection (DAD) not supported
• No routing protocol support (RIP, OSPF, etc. etc.), only static routes
• Software based forwarding