How about iptables -A OUTPUT --destination ${GATEWAY_1} -j TTL --set-ttl 2 (or 1, I'm not sure if the ttl dec is done at all with output chains) So, after the next hop, if the IP address isn't GATEWAY_1, then the packet is dead in the water. Ming-Ching Tiew wrote: > I am also having some difficulty in doing dead gateway > detection using a shell script :- > > Basically I am using ping -c 1 ${GATEWAY_1} If it times > out, I supposed it got into error, so it is probably time for me to > change route. > > However, even if the ping comes back, it does not mean the > GATEWAY is alive as my nexthop; this is because I figured > that the packet could have made a U-turn via the one of the alive > links to come back to answer the ping request, ie the gateway is > alive for a packet on the external network, but the gateway > is still down from inside point of view, and this can happen > due to a faulty connection between by second link IP and the > second link gateway ! > > Without patching the kernel to do dead gateway detection, > how do I find out if a particular gateway is dead as my > NEXTHOP ? > > > > > > > _______________________________________________ > LARTC mailing list / LARTC@xxxxxxxxxxxxxxx > http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: > http://lartc.org/ _______________________________________________ LARTC mailing list / LARTC@xxxxxxxxxxxxxxx http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/