Need help with 1811

Unanswered Question
Mar 7th, 2008


I am trying to configure 1811 to do load balance and failover. I added track on static rout and DHCP but as soon as i do that i lose internet connectivity, when I checi fastethernet0 connection in SDm it says no exit interface found please help.

I have this problem too.
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Edison Ortiz Sat, 03/08/2008 - 09:32

Hi Sergiy,

I don't see any NAT configuration on the file you posted. You have the NAT inside at the ingress interface and NAT outside on both egress interfaces but I don't see the source-list for this translation.

On that note, It's very hard to perform load-balancing when NAT is involved.

As the packet enters the router, the source IP will match the ACL from the NAT and a corresponding external IP will be given.

If this external IP belongs to ISP A but the routing decision is made to go via ISP B, then the packet will die as it leaves the router because ISP B isn't allowing IPs from ISP A as transit. The same concept can be seen when packets leave out of ISP A but with source IP belonging from ISP B.

At best, you can configure this router for failover. In the past, I worked in a similar scenario with another forum member, please see detail here:




sryzhykov Mon, 03/10/2008 - 06:39

Thanks for the reply Edison,

I had thouse 2 lines in the original config

ip nat inside source route-map dhcp-nat interface FastEthernet1 overload

ip nat inside source route-map fixed-nat interface overload

but for some reason they dissapeared when i was trying to add OER :-(. I added them back but still unable to browse internet, when checking fastethernet0 connection with SDM it errors out saying that exit interface is not found. The only one way to get it working id to delete tracjk 123 from the static route any suggestions?

As per load balancing goes is it totaly imposible to do it on NAT?

Edison Ortiz Mon, 03/10/2008 - 17:36

Hi Sergiy,

I don't understand how OER would delete an IP NAT. Anyway, please follow the link I posted and try to mirror that configuration to your network. It should work and if it doesn't tell me where it breaks. You should also be running a 12.4(x) code since OER features are pretty new.

You can load balance with NAT if you split the source network into half. You can have a source list pointing to an ISP that serve hosts from .1 .127 and another source list from .128 to .254 pointing to the other ISP.

That's some sort of load balance.





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