Static NAT on one ISP with default route on different ISP

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Nov 12th, 2009
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We have one router with connections to two different ISPs. Static NATs are configured to servers using IPs from ISP A. The customer is migrating everything eventually to ISP B. At this moment, we want to make all outbound traffic flow through ISP B but keep the static NATs to the servers on ISP A.


default route - ISP B

server 1 static NAT ISP A

server 2 static NAT ISP A

server 3 static NAT ISP A


The problem is that once ISP B is the default route, the static NATs break. How do we get traffic meant for the servers that comes in ISP A to return through ISP A?

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Jon Marshall Thu, 11/12/2009 - 09:14
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Jason


You can use PBR for this ie. traffic with a source address of one of the servers is sent to the ISP A next hop eg.


access-list 101 permit ip host any

access-list 101 permit ip host any

access-list 101 permit ip host any


note the server addresses would need to be the real address ie. not the natted ones.


route-map PBR permit 10

match ip address 101

set ip next-hop


then on the LAN interface of your router


int fa0/0

ip policy route-map PBR


Jon

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