Re: Debian boxes not replying to multicast and broadcast pings

[Urs Thuermann <urs@isnogud.escape.de>]

Jeff D <fixedored@gmail.com> writes:

> if you want it to reply to broadcast pings:
> echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

Ah, thanks.  This not only causes replies to broadcast pings to be
sent but also multicast to 224.0.0.1 (which is allhosts multicast and
essentially the same as broadcast).

> but, its turned off by default for security reasons, to avoid smurf
> attacks, which will try to flood a host with icmp ping requests.

When I looked yesterday, I've seen that file and I seem to remember it
already contained 0.  Today it was 1, so probably my memory on this is
wrong.

Also, I may have not looked that much at icmp_echo_ignore_broadcasts,
since I was actually more after multicast.  The ping to broadcast was
just a additional test.


urs