PBR using URL

snarayanaraju · ‎10-13-2009

Hi Experts,

I have a basic requirement in my network. I have 2 ISPs connected to Cisco Router. NAT is configured with per destination load balancing.

My customer wants when he access site www.abc.com It should always prefer ISP-1 and when ISP-1 is down, only then it should go to ISP-2.

The catch is I donot have any information on the IP address of www.abc.com & since the IP will be changing it is not feasible to determine the IP address too and configure manually using POLICY ROUTE-MAP.

My understanding is I can match only IP address inside the route-map & apply it in interface using command policy route-map Command

Kindly help me how to achieve this

Thanks in advance

Sairam

Giuseppe Larosa · ‎10-13-2009

Hello Sairam,

a possible approximate solution is that you need to resolve the URL with a DNS and to update the ACL accordingly.

the ip address can change over time but not every few minutes.

However, if some forms of DNS load balancing are used using multiple DNS queries may be a way to find out if you need to consider multiple IP addresses at the same time.

Another approach is that of finding out current DNS resolution and then using looking glass you can find what AS number owns the ip address.

Then you look for IP subnets of that ASN.

The reasoning is that the site can be hosted in multiple servers but all ip addresses may belong to the same provider/ organization.

Hope to help

Giuseppe