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New Member

NAT problem

I am studying NAT configuration and have setup two routers for in/out NAT and redundancy. I want to setup the LAB likes this, if the R1(2509) wan link goes down, the floating route come up and the traffic are route through R2 (3700).

But I have a problem on R1 when the wan link is DOWN. The traffic does’t routes to R2 even the correct route shown in the routing table.

When I ping the remote host (, R1 just simply reply the icmp directly (it acts as the remote host), but the traffic does’t transmitted to the target host…

If I replaced the R1 with a Cisco 3700 then the fail over working well….

If I removed the “ip nat outside source” statement and access the remote host directly (, the fail over working too. .

Anyone tell me why the configuration does't work on the 2509 ?

R1 – 2509 12.1(27a)

R2 – 3700 12.3(15)

Here is the configuration of the R1.

interface Loopback1

ip address


interface Ethernet0

ip address

ip nat inside


interface Serial0

ip address

ip nat outside

encapsulation ppp

no ip mroute-cache


ip nat inside source static

ip nat inside source static

ip nat outside source static

ip classless

ip route Serial0

ip route 20

ip route

New Member

Re: NAT problem

very strange.... after rebooted the router, it works!