Rotary NAT - TCP Load Distribution

Unanswered Question
Jan 14th, 2008

I'm using rotary NAT on a pair of 2600 Routers to translate the same IP to two different destinations using TCP load distribution.

Everything works fine except when you fail one of the physical servers. The Router will still try and NAT you to an IP that is no longer available basically blackholing your data.

Has anyone found a way round this or used another NAT feature? I'm not after any load distribution but more a redundancy approach using one IP to two physical devices. I will also be looking at configuring Stateful NAT across the two routers as well.

Any help is appreciated.



I have this problem too.
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Jon Marshall Mon, 01/14/2008 - 10:15

Hi Wayne

As far as i know what you are trying to do is not possible. The problem is that the 2600 router is not checking whether or not the server is alive before using the NAT translation.

To do what you are trying to do requires a device that can send probes to the servers to establish their availability. Some of the Catalyst switches support SLB (Server Load Balancing) but i don't believe the 2600'S do.

Even though i appreciate you only want resiliency if you want to do this at the network level you would need something along the lines of a loadbalancer because it has the extra intelligence needed.



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