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New Member

Multicast and NAT

This is continuing from:

Network Infrastructure / LAN, Switching and Routing / Configuring IGMP on 2950 Switches

I have successfully set up multicast routing on my network. The router (1760/2621) is a multicast router, the 2950 switches are only sending multicast traffic to the necessary ports and everything appeared to be going well. Bandwidth is being utilized as well as can be expected.

I am, however, experiencing an issue with NAT on the router sub-interface that is configured for multicast. Whenever I try to come into the network from the outside, either using static NAT or extendable PAT, the NAT session appears to be setup but the connection never occurs. I'm looking at "show ip nat translation" and the NAT session is listed, but I am unable to connect to the device. This is for all ports that are configured using either of these statements:

ip nat inside source static

ip nat inside source static tcp 3389 3389

Here is the relavant multicast config I am using:

ip multicast-routing

int f0/0.6

ip address

ip pim spare-dense-mode

I have several reasons to suspect the multicast configuration:

1) When I remove the multicast config from the sub-interface, it works fine.

2) When I connect from an "outside" interface (GRE tunnel, for example) that doesn't use NAT, it works fine.

3) When I connect to a device on a different sub-interface that doesn't use multicast, it works fine.

I need to leave multicast enabled on this sub-interface and I need to have the NATs work.

Any suggestions?


New Member

Re: Multicast and NAT

Hello JKOUT,

I would like to established a TV channel multicast setup, i have L3 (3550) switches, and L2(2950) switch, client r connected with a 2950 switches, same scenario which u r using,

Can u please tell me the exact/whole scenario, which u established,


what u configure on a router, and switches, what type of TV channel device u use,

I will be very thankfull to u,