23 Jan
2013
23 Jan
'13
5:18 a.m.
On Wed, 23 Jan 2013, Marius Petrescu wrote:
@Lynwood: RIP44, is a UDP communication, using src and
dest port 520,
multicast address 224.0.0.9 as destination and source is 44.0.0.1.
Before receiving these broadcasts the user have to join a multicast group
and enable multicast on the receiving interface.
This is why you need a route to 44.0.0.1 on the tunnel interface, so that
the group subscribe message gets sent to 44.0.0.1.
Feel fre to use a network sniffer like wireshark and see for yourself.
This is a little bit inaccurate too. UDP yes, and addresses are right, and
yes, it is multicast.
The 44.0.0.1 gateway is a bit simplistic implementation of RIP and
multicast. It transmits the RIP packets, encapsulated in ipip packets,
even if you do *not* transmit the IGMP "join multicast group" packet. You
do not need to have a route to 44.0.0.1 on the tunnel. As soon as your
gateway is in the encap file, the 44.0.0.1 gateway will start transmitting
the RIP packets towards your gateway, even if it's offline.
My whole rip44d startup goes like this, and works fine:
/sbin/ip route add blackhole 44.my.net.0/24
/sbin/ifconfig tunl0 44.139.my.gwaddr up || exit 2
/usr/local/sbin/rip44d -p passwordhere < /dev/null &
If you run tcpdump/wireshark on your gateway which does not run RIP,
you'll still see the RIP packets coming in. No need to send IGMP JOIN
packets. Linux might transmit it when you fire up rip44d, though, but
44.0.0.1 won't care much.
- Hessu