NAT on GRE tunnel traffic

[jeffreywatson]

Can someone tell me if its possible to do this and if so how.

I need to setup a gre tunnel between two routers and tunnel multicast over a WAN.

When the packets enter the tunnel the source address is 172.31.x.x group 239.252.x.x

when they exit the tunnel on the receive side i need the packets 

to have a source address of hte tunnel interface with teh same group.

I can setup the tunnel and get the multicast through etc.

is there a way to NAT the traffic as it exits the tunnel to the new source address ?

[rvarelac]

Hi Jeffrey, 

I think that is not possible , because GRE is a portless protocol ,  there is not source or destination port on the connection , just the protocol 47. 

You might try a solution as GRE over IPSEC to be able to NAT the IPs.

Hope it helps

-Randy-

[sushanth.shetty]

It can be done. Look at multicast service reflection. 

[Georg Pauwen]

Hello,

which PIM mode are you using to get the multicast traffic over the GRE tunnel ? I want to lab the suggestion made below about Multicast Service Reflection, the only restriction is that it doesn't work with PIM dense mode...

[sushanth.shetty]

Using sparse mode. Make sure to statically join the IGMP Group on your virtual interface. As far as I remember service reflection is not supported in pim-dense mode.