Multicast forwarding

[ah6511]

Hi,

I have a Ubuntu 7.1 box with 2 ethernet interface. I want to enable multicast forwarding. So I tried following with root account:
echo 1 > /proc/sys/net/ipv4/conf/all/mc_forwarding
echo 1 > /proc/sys/net/ipv4/conf/eth0/mc_forwarding
echo 1 > /proc/sys/net/ipv4/conf/eth1/mc_forwarding

But always gor permission denied.
I also tried with sysctl and got same thing.

I was able to do the following though:
echo 1 > /proc/sys/net/ipv4/ip_forwarding

Any reason? TIA

[ah6511]

I just noticed /proc/sys/net/ipv4/conf/all/mc_forwarding is read only. But adding write privilieage under root still failed with permission denied.