2007-08-06 23:37:58

by Adam McLaurin

Subject: Creating virtual interface triggers an IGMPv3 Join to Multicast DNS

Hi folks,

For some reason, every time I create a virtual interface (using tun),
the interface immediately generates an IGMPv3 Join packet for group
224.0.0.251, which (according to Google) is Multicast DNS.

This packet is generated automatically and consistently. I'm wondering
why this should be the case, and if it can be disabled.

Thanks,
Adam

2007-08-07 04:30:57

by Kyle Moffett

Subject: Re: Creating virtual interface triggers an IGMPv3 Join to Multicast DNS

On Aug 06, 2007, at 19:37:47, Adam M wrote:
> Hi folks,
>
> For some reason, every time I create a virtual interface (using
> tun), the interface immediately generates an IGMPv3 Join packet for
> group 224.0.0.251, which (according to Google) is Multicast DNS.
>
> This packet is generated automatically and consistently. I'm
> wondering why this should be the case, and if it can be disabled.

You don't happen to be running "avahi" or one of the other Zeroconf/
Bonjour/Rendezvous/$P2P_BUZZWORD_OF_THE_WEEK local-network-discovery
daemons, do you? Most of those keep an eye out for new network
interfaces and automatically start pushing multicast packets down
them as soon as they appear, which is the most likely explanation for
what you are seeing; as opposed to a kernel issue.

Cheers,
Kyle Moffett

2007-08-07 13:15:35

by Adam McLaurin

Subject: Re: Creating virtual interface triggers an IGMPv3 Join to Multicast DNS

Hi Kyle,

Ah-hah, you nailed it right on the head. I unknowingly had Bonjour
running (must be installed by default on Fedora Core 3), which started a
process 'mDNSResponder'. I'm guessing that's the bugger that's fire off
these multicast joins.

Thanks for the tip!

-Adam


On Tue, 7 Aug 2007 00:30:36 -0400, "Kyle Moffett" <[email protected]>
said:
> On Aug 06, 2007, at 19:37:47, Adam M wrote:
> > Hi folks,
> >
> > For some reason, every time I create a virtual interface (using
> > tun), the interface immediately generates an IGMPv3 Join packet for
> > group 224.0.0.251, which (according to Google) is Multicast DNS.
> >
> > This packet is generated automatically and consistently. I'm
> > wondering why this should be the case, and if it can be disabled.
>
> You don't happen to be running "avahi" or one of the other Zeroconf/
> Bonjour/Rendezvous/$P2P_BUZZWORD_OF_THE_WEEK local-network-discovery
> daemons, do you? Most of those keep an eye out for new network
> interfaces and automatically start pushing multicast packets down
> them as soon as they appear, which is the most likely explanation for
> what you are seeing; as opposed to a kernel issue.
>
> Cheers,
> Kyle Moffett
>