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New Member

Load balance outgoing traffic on CISCO 1812

Hi all!

I am trying to achieve a round-robin destination based outgoing load balancing on my CISCO 1812 box (after I have realized that no OER support will be available on my modell...) to the Internet. I have two external ethernet ports: one is connected via PPOE DSL link to ISP1. Here we have only one IP address so I have to use NAT. The other is a routed connection to ISP2. ISP2's assigned IP range is segmented into two parts. The first is assigned to the external interface, the other is assigned to the internal interface (wich acts as a DMZ wiht Internet IP addresses).

So: connection 1 translates ISP2's IPs to ISP1 single IP via NAT when that is the outgoing direction, connection 2 simply routes the traffic. And that is where the problem comes in. I set up the connections, routing and NAT accordingly have added two equivalent routes to the Internet.

Now then if I enable only one connection at a time the Internet is reachable without problem. Direct routing works in one case and NAT works fine in the other. But when I have both outgoing connections enabled, the NAT seems to be non-functional, packets going out the DSL interface without source address translation and ISP1 sees ISP2-s IP as the source...

What could be the problem? Why doesn't NAT work when both connections are enabled?

Thanks for any help in forward!

Arnold Domschitz


Re: Load balance outgoing traffic on CISCO 1812


AFAIK SPs wont route other SPs ip block in their own nework also is it possible to post out the config with ip address supplier specifications like ip provided by SP1 or SP2 ??


New Member

Re: Load balance outgoing traffic on CISCO 1812


The relevant part of the configuration is attached.


ISP2's address range is: X.Y.Z.224/27 what is segmented as:

Fastethernet0 (external): X.Y.Z.241/28

Vlan1 (internal): X.Y.Z.224/28

ISP1's only IP is: K.L.M.49

There are some static translations and policy based routing in the config wich seem work fine. The only thing broken is the otugoing load balancing when both of the external interfaces are enabled (or I do no redirect the traffic to one gateway via policy)

Hope it helps lighten things up a bit...