Dynamic re-routing when a VIP goes down?

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Aug 5th, 2009
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Is there a handle/mechanism on a VIP so that when a primary VIP load balancing on an ACE appliance connected to a 3750 and then a 2821 goes down so that the 2821 will then advertise a new route to the a remote location acting as the backup?

Currently this is done manuualy to chnage the routes, but want to see if there is a way to detect the primary VIP going down so the 2821 will drop the route to primary VIP and re-route to the backup VIP via EIGRP or OSPF?

Theo Van Dyne

Cisco network Engineer

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Jon Marshall Wed, 08/05/2009 - 11:00
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Not sure if there is anything built into the ACE but you should be able to achieve what you want by using IP SLA on the 2821 and tracking the availability of the VIP using ICMP.

Could you perhaps knock up a quick topology showing addressing etc.


theovandyne Thu, 08/06/2009 - 13:41
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I did some more research on the net (bing.com) and found how to install a static route when the ip sla fails for the primary VIP.

See if this is what you were thinking? I think it will work for us, though we may have to manually take out the route to to to the backup VIP when the primary VIP comes back up.

When I have the new route installed, I wuld install it with a smaller administrative distance so it would prefer it over the same static route to the primary VIP, but with a higher administrative distance.


Theo Van Dyne



Install a static route when an IP address is NOT reachable

In my February IP corner article, Small Site Multihoming, I've described how to install a static route based on reachability of a remote IP address (as measured with the IP SLA feature of Cisco IOS) and one of my readers recently asked an interesting question: “How do you install a static route when an IP address is not reachable?”

Without going into the design reasons that prompted the question, you can actually track when IP SLA measurement fails with an obscure configuration syntax of the track objects.

In my example, the route to would be inserted in the IP routing table when the ping to fails:


! Define and start the IP SLA probe


ip sla 53


timeout 500

frequency 3

ip sla schedule 53 life forever start-time now


! Define an object that tracks the SLA probe


track 13 rtr 53 reachability


! Define another object that is the negation of the previous object


track 14 list boolean and

object 13 not


! Insert a static route if the second object is UP (thus the

! IP SLA probe failed)


ip route Null0 track 14

Note: This article is part of You've asked for it series.



Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or visit his page on Facebook.


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