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 ?
>
>
>
>
>
>
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