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New Member

NAT with multiple ISP's ?

Hello,

can someone explain to me how to configure a NAT scenario that will cause the router to switch to the second ISP interface for translation if the primary fails. There is no BGP failover involved, just floating static routes. I think I know part of the solution below, I just don't know the rest. thanks..

e0 is ISP 1 (primary) with NAT outside

e1 is ISP 2 (secondary) with NAT outside

e2 is LAN with NAT inside

default route to ISP1 AD is 1

default route to ISP2 AD is 2

ip nat inside source route-map ISP1 interface ethernet 0 overload

ip nat inside source route-map lSP2 interface ethernet 1 overload

route-map ISP1 permit 10

match interface ethernet 0

route-map ISP2 permit 10

match interface ethernet 1

use of the route map statements will cause nat to consult the routing table to see if the lowest AD route is there for the trans, right ? will this do what I want ????

2 REPLIES
Bronze

Re: NAT with multiple ISP's ?

Yes this scenario will work. You will also want to add an acl for NAT and put it under both route-maps:

access-list 1 permit x.x.x.x 0.0.0.255

route-map ISP1 permit 10

match interface ethernet 0

match ip address 1

!

route-map ISP2 permit 10

match interface ethernet 1

match ip address 1

When going from an inside interface to an outside interface (e2 -> e0, e2 -> e1) routing occurs before the translation takes place. So if the default route is pointing out e0, the routing decision is made, then the local to global translation is made accordingly.

New Member

Re: NAT with multiple ISP's ?

thanks, I will add the ACL...

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