[KLUG Members] iptables NAT problem

[John Pesce]

Hi all,

I'm rather new to iptables and I have a new problem I can't figure out
from the howtos I've run across.

1) Is there a current detailed description/howto for iptables?

2) here is my situation

I have a linux box with three interfaces

eth0 192.168.3.1
eth1 10.7.35.2
eth2 192.168.2.1

I'm running PIMd on it to route multicast traffic between the subnets.

Also on the 10.7.35.0 subnet is another multicast/PIMd aware router that
is part of another external private multicast network made up of other
10.7.* subnets. The routers on those subnets are only aware of the
10.7.* subnets and have access lists only for 10.7. traffic.

My problem is that multicast traffic coming from my 192.168.* subnets
don't have 10.7.* source addresses and are dropped by the 10.7.* routers

I need my 192.168.* sourced multicast traffic to be distributed on that
private 10.7.* multicast network.

How can I change my 192.168.* packet source addresses to look like they
are coming from my linux PIMd router, say 10.7.35.1 without messing up
PIMd?

It sounds like I should setup some kind of NAT POSTROUTE to rewrite the
source address on packets leaving the eth1 interface destined for 224.*
to a source IP of eth1 ?

Is this reasonable? Is there a better way?

Thanks