2 wan on a single router

Unanswered Question
Mar 18th, 2008


i have a single 2811 with 2 wan links first one is E1 on E1 controller and the second links is through a DSL modem to one of the ethernet ports on 2811. these 2 wan links are from 2 different ISPs. i have a webserver on my private network. what i want to acheieve is traffic for the webserver entering 2811 using E1 should be responded using the E1. And traffic entering 2811 through dsl for webserver should be responded by the same DSL link. this is something called symmetric routing. can anyone help? thnaks in advance


I have this problem too.
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Paolo Bevilacqua Tue, 03/18/2008 - 03:54

Hi, the configuration changes a little if you're using nat or not. If using nat, no worries nat takes care of making routing symmetric.

If not, you need to setup policy routing so that packet source from the webserver alwasy go out the E1 circuit.

As improvement you could get an HWIC-1ADSL so that you can eliminate the external modem and have control for the circuit directly on the router.

srmumtaz01 Tue, 03/18/2008 - 05:05

thanks for replying.

but the problem persist as i cannot nat between 2 wan interface ip addresses to a single web server.i am using the following command for natting.

ip nat inside source static tcp ( web server private ip) 80 int serial 0/0/0:2 80

i cannot establish another nat with different wan link to the same web server.

another problem that i am experiencing is that the wan link to which default gateway is pointing to ; only works. the other one does not.

please help.



Paolo Bevilacqua Tue, 03/18/2008 - 05:48

Have you disable router local web server "no ip http server" ? What error do you receive when trying to enter the second nat command ?

Also what it means the other one doesn;t work ?

srmumtaz01 Tue, 03/18/2008 - 23:20


i will look into disabling ip http server.

when i try to issue another nat command for the same web server but from the 2nd wan link the first nat gets replaced.

if a client is accessing the webserver uding the ip from wan link A and my default gateway is set to wan link B. the web page is not displayed to client.

I have a very basic issue that i am experiencing these days. i have studied that tcp connection are end to end ::::meaning that tcp connection are between end systems and they do not rely/depend on the intermediate routes and links. but this is not happening. if a tcp connection request is coming from wan link A and my default gateway is set to wan link B, tcp connection does not form.

any ideas what i may be missing here.

PLz help. thanks


Paolo Bevilacqua Wed, 03/19/2008 - 03:17

Hi, end systems have default gateway, routers have routes and default route. Your router with two internet circuits will need to have two default routes, eg:

ip route serial0/1:0


ip route z.z.z.z

And two nat statements as well.


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