[LARTC] dual-isp incoming traffic problems

[David Boreham]

Daniel Wittenberg wrote:

>I have two ISP connections, and am having some issues.  I can connect to
>any services on the firewall, like the smtp gateway, but anything on the
>internal server only works from one connection. 
>
I think we do what you're trying to achieve, but before I spend
the time to dive into the details, let's confirm what you're looking to do:
You have two upstream connections and separate public IP
subnet allocations from each ISP, yes ? You're not running BGP, right ?
You have a single Linux router that has three physical interfaces :
one connects to ISP A, the next to ISP B and the third to the internal
network, correct ?

Let me know if I got all this right. If so then we run much the
same setup here and I can tell you how we configured it
(I do remember it took several days of reading kernel
source code and tcpdump'ing to get it all working).