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Cisco - IP SLA Route flapping

Posted on 2009-07-16
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Last Modified: 2012-05-07
Hi,

I have set up IP SLA to monitor an Internet IP address (a DNS server that is always up) so I can change the default gateway on my router in the event of my primary internet dropping. The problem is that when the router changes its gateway to point to my other Internet connection, the IP SLA command now see's that IP address it's tracking as back up and flips back to the original route, which isn't there and so flips back again....and so on

here is the 'debug track' output

000706: 11:01:58: Track: 1 Change #94 rtr 1, reachability Up->Down
000707: .Jul 16 15:48:42: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000708: 11:02:03: Track: 1 Change #95 rtr 1, reachability Down->Up
000709: .Jul 16 15:48:47: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000710: 11:02:08: Track: 1 Change #96 rtr 1, reachability Up->Down
000711: .Jul 16 15:48:52: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000713: 11:02:13: Track: 1 Change #97 rtr 1, reachability Down->Up
000714: .Jul 16 15:48:57: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000715: 11:02:18: Track: 1 Change #98 rtr 1, reachability Up->Down
000716: .Jul 16 15:49:02: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000717: 11:02:23: Track: 1 Change #99 rtr 1, reachability Down->Up
000718: .Jul 16 15:49:07: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000719: 11:02:28: Track: 1 Change #100 rtr 1, reachability Up->Down
000720: .Jul 16 15:49:12: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000721: 11:02:33: Track: 1 Change #101 rtr 1, reachability Down->Up
000722: .Jul 16 15:49:17: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000723: 11:02:38: Track: 1 Change #102 rtr 1, reachability Up->Down
000724: .Jul 16 15:49:22: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000725: 11:02:43: Track: 1 Change #103 rtr 1, reachability Down->Up
000726: .Jul 16 15:49:27: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000727: 11:02:48: Track: 1 Change #104 rtr 1, reachability Up->Down
000728: .Jul 16 15:49:32: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000729: 11:02:53: Track: 1 Change #105 rtr 1, reachability Down->Up
000730: .Jul 16 15:49:37: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000731: 11:02:58: Track: 1 Change #106 rtr 1, reachability Up->Down
000732: .Jul 16 15:49:42: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down
000733: 11:03:03: Track: 1 Change #107 rtr 1, reachability Down->Up
000734: .Jul 16 15:49:47: %TRACKING-5-STATE: 1 rtr 1 reachability Down->Up
000735: 11:03:08: Track: 1 Change #108 rtr 1, reachability Up->Down
000736: .Jul 16 15:49:52: %TRACKING-5-STATE: 1 rtr 1 reachability Up->Down

Does anyone know a work around, as this seems a powerful tool?

Thanks,

Ally
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Question by:ally0000
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Expert Comment

by:clonga13
ID: 24871619
Don't ping something that can be found with either connection. I usually ping the other end of my ISP connection. If the line goes down, then the other would usually show down down and wouldn't ping.
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Author Comment

by:ally0000
ID: 24872067
Hi, thanks for the quick reply, so pinging something like my ISP-provided DSL modem's gateway? Or should I set it to ping the DSL modem?

Thanks
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clonga13 earned 500 total points
ID: 24872107
The DSL modem would probably always respond and never show a line failure. I would go with the DSL modem's gateway. If the line goes down, then it definetly won't ping.
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Author Comment

by:ally0000
ID: 24872118
cool, thanks a lot...I'll get this set up tomorrow
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