[XCSSA] Multicast routes

[xcssa@xcssa.org]

I have a computer with 2 NICs, one inside, one outside facing. I want
to route all Multicast traffic to the outside NIC. So I bring up the
interface:

ifconfig eth1 up

Then run route for my Multicast address space:

/sbin/route add -net 224.0.0.0 netmask 240.0.0.0 dev eth1

and I get:

SIOCADDR: no such device

I can only route the Multicast traffic if I assign the NIC and IP. I
thought you didn't need an IP address assigned to the outside NIC
because all its handling is Multicast traffic.

One problem with assigning an IP address is that I have to iptables
the interface to protect it. So I have a small script that blocks all
tcp and allows all UDP to eth1:

/usr/sbin/iptables -F

/usr/sbin/iptables -N FIREWALL
/usr/sbin/iptables -A FIREWALL -i eth1 -s 224.0.0.0/4 -p udp -j ACCEPT
/usr/sbin/iptables -A FIREWALL -i eth1 -p tcp -j DROP
/usr/sbin/iptables -A INPUT -j FIREWALL

The second problem is after running the iptables script is that for
some reason the computer wants to route DNS lookups to eth1 instead of
eth0. I did not set a gateway route for eth1, only an IP address, so I
don't understand why it insists on using eth1 for DNS lookups.

Can anybody shed some light on this???


-- 
Jeremy