On Tue, 17 Apr 2007, Urs Thuermann wrote:
I have currently 4 Linux machines in my network, one embedded system
running Linux-2.4.20, a system build from scractch over the last 13
years running 2.4.34.2 and two Debian boxes, both running Debian's
Linux kernel 2.6.18-4-686.
When I ping to the broacast address or the allhosts multicast address
I get replies from the embedded and the self-built sysem, but not from
the two Debian boxes:
<snip ping tests>
Also, I have written two small test programs, udp-ping and udp-echo,
which send short packets two a specified UDP port and echo all packets
to a certain UDP port, respectively. If I send UDP packets to the
multicast address, udp-echo will answer, also on the Debian machines.
This shows that the Debian machines are able to receive multicast.
So what is the reason, that the 2.6.18-4-686 kernel does not reply to
ICMP echo request to broadcast and multicast address? I've looked
through /proc/net and /proc/sys/net but haven't found anything which
looked relevant.
urs
if you want it to reply to broadcast pings:
echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
but, its turned off by default for security reasons, to avoid smurf
attacks, which will try to flood a host with icmp ping requests.
hth,
jeff
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