# mrouted, bridge and iptables nat table

## Bircoph

Hello,

I have successfully setup a multicast router between multiple networks using mrouted,

but I need to implement some "advanced" features concerning multicast routing and I

struck with them.

1) I have a bridge interface br0 connected to mrouted. When there are subscribed

multicast users on this interface, I want mrouted to send multicasts only to those bridge

port(s) where these subscribers are, not to the whole br0 interface. How can I achieve this?

2) This is peculiar, but after mrouted is started, multicast packets do not traverse nat table

in the iptables (-j TRACE shows that nat table is not affected at all by multicasts after mrouted

was started). I want to do some fancy things there (and as to my knowledge ip source

mangling can't be done in any other table). So I need either to make multicast somehow

traverse the nat table, or mangle ip source in another place.

----------

## AngelKnight

 *Bircoph wrote:*   

> Hello,
> 
> I have successfully setup a multicast router between multiple networks using mrouted,
> 
> but I need to implement some "advanced" features concerning multicast routing and I
> ...

 

CONFIG_BRIDGE_IGMP_SNOOPING

 *Bircoph wrote:*   

> 2) This is peculiar, but after mrouted is started, multicast packets do not traverse nat table
> 
> in the iptables (-j TRACE shows that nat table is not affected at all by multicasts after mrouted
> 
> was started). I want to do some fancy things there (and as to my knowledge ip source
> ...

 

Not sure about this bit, maybe someone else has a better idea.  Perhaps Linux Advanced Routing and Traffic Control can shed some light?

----------

## Bircoph

 *AngelKnight wrote:*   

> 
> 
> CONFIG_BRIDGE_IGMP_SNOOPING
> 
> 

 

It was already enabled:

```

CONFIG_BRIDGE_IGMP_SNOOPING=y

```

but nevertheless tcpdump shows what I wrote before.

 *Quote:*   

> 
> 
> Not sure about this bit, maybe someone else has a better idea.  Perhaps Linux Advanced Routing and Traffic Control can shed some light?

 

Oh, no. This is the first document I started to read when I was curious about multicast. And it is extremely poor about multicast (but good in other subjects).

----------

