route-map case

There is a someone wants to configure such scenario.
if the router see some port then use a gateway, the solution is using route-map and apply it to the interface.

conf t
route-map port80
match ip address matchport80
set ip next-hop xxx.xxx.xxx.xxx <----------- the gateway ip you set for next-hop for the http traffic


ip access-list extended matchport80
 permit tcp any any eq www

interface FastEthernet0/0
 ip policy route-map port80