From: Denis Fedorishenko <nuclearcat@nuclearcat.com>
To: lartc@vger.kernel.org
Subject: Re[2]: [LARTC] script to perform dead gateway detection
Date: Thu, 11 Mar 2004 07:39:11 +0000 [thread overview]
Message-ID: <277287922.20040311093911@nuclearcat.com> (raw)
Hello Daniel,
Thursday, March 11, 2004, 4:55:15 AM, you wrote:
Maybe better just to use
ping -t 2 anyhost
:)
DC> How about iptables -A OUTPUT --destination ${GATEWAY_1} -j TTL --set-ttl
DC> 2 (or 1, I'm not sure if the ttl dec is done at all with output chains)
DC> So, after the next hop, if the IP address isn't GATEWAY_1, then the
DC> packet is dead in the water.
DC> 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@mailman.ds9a.nl
>> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO:
>> http://lartc.org/
DC> _______________________________________________
DC> LARTC mailing list / LARTC@mailman.ds9a.nl
DC> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
--
Best regards,
Denis mailto:nuclearcat@nuclearcat.com
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/
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