Hi,
I would never suggest to run default routes in the situation when you have 2 different ISP's feeding the internet to you.I would rather look for more controlled and filtered way for sending the traffic from 2 different ISP's.The idea behind this is that with default routes you dont know that traffic will hit which router and will use which link to go out forexample if you have a slow wan link and a high speed wan link, with default routes you dont have control over sending a majority of traffic thorugh high speed wan link and a little low traffic over the slow speed wan link. Another problem here would be of Assysmteric routing in which tarrfic for internet might use one ISP link and the return traffic will come all the way via internet traffic through the second ISP.This is where the slowness comes into the picture.
If I were you, I would have thought of using NAT and PBR (policy based routing).I would first look at the kind of traffic, users, applications that I have to go the outisde world. Once the traffic is determined I would see the traffic distribution of the users over the two links. I would use my application, mail traffic to go thorough one link and internet and other traffic to use another link.I will make both the links as back up of each other.In case of one of the link goes my all the traffic will use the other link. I would suggest to implement proper QOS and rate limiting to drop the unwanted traffic.
NAT:
http://www.cisco.com/warp/public/556/12.html
Policy Based Routing:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/qos_c/qcpart1/qcpolicy.htm
www.cisco.com/warp/public/732/Tech/plicy_wp.htm
QOS:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/qchintro.htm
HTH,Please rate if it does.
-amit singh
