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slimbls
2005-08-03, 19:53
Hi, slimserver newbie here...I have a suse 9.2 linux system that's my firewall and media server (please, no bottle tossing this way).

After I installed slimserver (6.1.1) I asked it very nicely to only use my internal ethernet, but I'm still seeing UDP packets from myself on port 5353 to 224.0.0.251.

How can I nicely tell mDNS to not broadcast on my external ethernet adapter besides a couple of lines in iptables?

Thanks!

Benn

Triode
2005-08-04, 10:22
> How can I nicely tell mDNS to not broadcast on my external ethernet
> adapter besides a couple of lines in iptables?
>
Do you use mDNS? You can stop it completely and the associated process by setting the Rendezous name to blank.

Other than that I don't think you can specify a port to multicast on as it is really the OS which is deciding how to send the
packets. They are from 224.0.0/24 so should not be forwarded by any routers.

slimbls
2005-08-04, 16:37
Thanks! I'll have to check and see what happens if I turn it off...

Phil Karn
2005-08-14, 23:06
slimbls wrote:
> Hi, slimserver newbie here...I have a suse 9.2 linux system that's my
> firewall and media server (please, no bottle tossing this way).
>
> After I installed slimserver (6.1.1) I asked it very nicely to only use
> my internal ethernet, but I'm still seeing UDP packets from myself on
> port 5353 to 224.0.0.251.
>
> How can I nicely tell mDNS to not broadcast on my external ethernet
> adapter besides a couple of lines in iptables?

mDNS stands for "multicast DNS" and that's how it works. Multicasting is
a lot like broadcasting, but scales much better because you can be
selective about who receives your packets.

mDNS is designed to let you find services and hosts on your local LAN
without needing a server on your local network. Requests for IP
addresses and services are multicast on the local LAN. Whichever machine
has the requested information will respond, and the others will ignore
it. mDNS is currently used most heavily by Mac OS X, which calls it
either "Rendezvous" or "Bonjour", and there are ports of mDNS to Linux.

224.0.0.251 is the standard multicast destination address for a mDNS
packet. Your router won't forward multicast packets unless it's
specifically designed and configured to be a multicast router, which it
almost certainly won't. Otherwise it'll just ignore them, and they'll
stay on your local network. So there's nothing to worry about.

Phil