What does this IPTABLE entry mean?

I know nothing about IPTABLES.
Playing around, I ran "# iptables -L" and found something weird.
In /etc.sysconfig/iptables there's this line:

-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT

What does that mean? I get that it has something to do with incoming
UDP packets on port 5353 from IP 224.0.0.251 are always accepted, yes?
Do I have that right?

I know nothing of that IP address. It's not familiar to me.

A whois on it gives me an error... so, I'm really hoping that it's one
of those reserved IP's like 127.0.0.1 that's a loopback, and some
service or something has a legitimate use for it.

Any feedback, much appreciated!
Liam

Edward Leiper wrote:
> That IP address is a multicast one used by mDNS - which Apple calls
> Rendezvous. I'd say that this rule is to allow your machine to
> receive query packets asking what services it is running. Have a look
> for a process called mDNSresponder or similar.
>
> ~Ed

Thanks for the reply!
I grepped a "ps aux" and found:

nobody 3473 0.0 0.0 13384 456 ? Ssl Oct28 0:00
mDNSResponder

Odd. Is that a good, bad, or indifferent thing? ("Apple?" This is a
Fedora 3 box. Weird.)

Well, I'll look into it.
Thanks again for the help!
-Liam

That IP address is a multicast one used by mDNS - which Apple calls
Rendezvous. I'd say that this rule is to allow your machine to
receive query packets asking what services it is running. Have a look
for a process called mDNSresponder or similar.

~Ed

If you want to serve mDNS for people in the internet then keep the entry.
If not delete it.
For you it doesn't make any difference.



(E-Mail Removed) wrote:
>
> Edward Leiper wrote:
>> That IP address is a multicast one used by mDNS - which Apple calls
>> Rendezvous. I'd say that this rule is to allow your machine to
>> receive query packets asking what services it is running. Have a look
>> for a process called mDNSresponder or similar.
>>
>> ~Ed
>
> Thanks for the reply!
> I grepped a "ps aux" and found:
>
> nobody 3473 0.0 0.0 13384 456 ? Ssl Oct28 0:00
> mDNSResponder
>
> Odd. Is that a good, bad, or indifferent thing? ("Apple?" This is a
> Fedora 3 box. Weird.)
>
> Well, I'll look into it.
> Thanks again for the help!
> -Liam