Linux ICMP redirects

It seems that Ubuntu 11.10 ships with a sample /etc/sysctl.conf which contains the following statement, intended to tell the system not to originate ICMP redirects when acting as a router:

# Do not send ICMP redirects (we are not a router)
net.ipv4.conf.all.send_redirects = 0

Unfortunately, (at least) with kernel 3.0 as shipped with Oneiric, even after setting this and activating with 'sysctl -p', it doesn't work.  Symptoms are noisy kernel log records such as:

[611513.083432] host 192.168.0.100/if2 ignores redirects for 8.8.8.8 to 192.168.0.1.

If you actually want to disable sending ICMP redirects, you have to explicitly set this per interface in /etc/sysctl.conf, by doing:

# Do not send ICMP redirects (we are not a router)

net.ipv4.conf.eth0.send_redirects = 0

net.ipv4.conf.eth1.send_redirects = 0

net.ipv4.conf.eth2.send_redirects = 0

etc.