What is solution of nat failover with 2 ISPs?

[weerapatr]

Now I have lease line links to 2 ISPs for internet connection. I separate packets of users by accesslist such as www go to ISP1 and mail or other protocol go to ISP2 . Let's say link go to ISP1 down I need www traffics failover to ISP2 and vice versa.

Problem is acl on nat statement?

If you config about this.

access-l 101 permit tcp any any www -->www traffic to ISP1

access-l 101 permit tcp any any mail --> back up for mail packet to ISP2 down

----------------

access-l 102 permit tcp any any mail -->mail packet to ISP2

access-l 102 permit tcp any any www --> back up for www traffic go to ISP2

ip nat inside source list 101 interface s0 overload

ip nat inside source list 102 interface s1 overload

In this case is links of ISP1 and ISP2 are UP.

when you apply this acl on nat statement then nat will process each statement in order( if I incorrect please correct me) so mail traffics will match in this acl and then nat with ip of ISP1 only.

please advice solution about this

TIA

[tdrais]

You best bet is to use routemaps on the nat statements to do this rather than the access lists.

You match the nexthop and use that to select the proper nat. In effect with a interface overload configuration you say use the interface that that traffic is going out of as the nat address for this traffic.

You control which path to select either by policy routing or normal routing.