[Xorp-hackers] Multicast routing

[Pavlin Radoslavov]

> Opening RAW socket for IPPROTO_IGMP, will get all IGMP packets regardless of
> its destination address from kernel to XORP.

I doubt this will happen if the interface wasn't in ALLMULTI state
(see my previous email on the subject).

> Can i know, where it says it will only get 224.0.0.1 packets. I'm not aware
> such a filtering in RAW socket.

The 224.0.0.1 packets are received only with the RAW socket because
every host is a member of the 224.0.0.1 (ALL-SYSTEMS) multicast
group (the kernel itself joins that group). For groups that have
been joined the interface doesn't need to be in ALLMULTI state.

Regards,
Pavlin

> Thanks,
> Regards,
> Suresh kannan.
> 
> 
> On 2/15/07, Sachin K <sachinutd at gmail.com> wrote:
> >
> > How does the XORP multicast router sniff IGMP/MLD messages from the
> > network?
> >
> > I checked the some routers' code. Most of them just open a RAW socket with
> > protocol set to IPPROTO_IGMP. But using this the router gets the
> > packets addressed to 224.0.0.1 only.
> >
> > How does it receive IGMPv2 and IGMPv3 membership reports sent by other
> > hosts?
> >
> > Thanks,
> >
> > Sachin
> >
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