2811 Router Connection

Unanswered Question
Jul 30th, 2007

If I wanted to add a backup Cable modem internet connection to my 2811 router that is currently running a 10 megabit ethernet handoff on its Ethernet WAN card, can I just add it to one of my ethernet ports?

One of the ethernet ports is used for the inside network. Can I make the 2nd ethernet port connect to the cable modem and use it as a backup Internet connection?

I wanted to setup policy-based routing and split certain traffic to go through the cable modem.

Can anyone advise?

I have this problem too.
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mohammedmahmoud Mon, 07/30/2007 - 12:39


As for using the link as backup internet, it can be easily done via a floating default static route (default route with higher AD), and yes you can use PBR at the inbound of the LAN port in order to route certain traffic out the cable modem, please check the following for PBR:

Policy-Based Routing


Configuring Policy-Based Routing



Mohammed Mahmoud.

the best way to go here is to use a recent IOS (something in 12.4 should work fine!) and implement two default routes with different AD (higher AD for cablemodem connection).

second, implement sla tracking or route tracking.

this allows for you to track any IP address of the primary internet connection (e.g. the IP of your Internet router) via ICMP. if this router ever goes down, the router will remove this route from its routing table (having been marked unreachable / invalid) and your backup route will be automatically installed.

you can tune this such that it fails over quickly or slowly, based on your needs.

also can use PBR for granular traffic engineering requirements (e.g. send SMTP traffic out backup connection so it does not "clog" primary connection). works great on ASA/PIX 7.2.2+ firewalls as well!


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