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Community Member

1841 to 3030 IPSec tunnel, no connectivity

Hello everyone,

I have a Cisco 1841 router with Adv Sec package on it and need to set up a static IPSec tunnel to a Cisco 3030 concentrator. The trick is that the interesting traffic has to be NAT'd through a different IP than the interface IP.

So the peering must happen on x.x.x.34, but encrypted traffic from me must come from x.x.x.35. This is a requirement of the office that I am connecting to. I've set up tunnels before, but never with this type of requirement.

What is the best way to accomplish this?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: 1841 to 3030 IPSec tunnel, no connectivity

Hi Sean

local network at 1841 end: 192.168.5.0/24

remote network at 3030 end: 172.16.5.0/24

on 1841

int loopback10

ip address x.x.x.35

access-list 101 permit ip 192.168.5.0 0.0.0.255 172.16.5.0 0.0.0.255

ip nat inside source list 101 interface loopback10 overload

Obviously in your crypto map access-list you need to use the Natted address ie.

access-list 102 permit ip host x.x.x.35 172.16.5.0 0.0.0.255

HTH

Jon

4 REPLIES
Hall of Fame Super Blue

Re: 1841 to 3030 IPSec tunnel, no connectivity

Hi Sean

local network at 1841 end: 192.168.5.0/24

remote network at 3030 end: 172.16.5.0/24

on 1841

int loopback10

ip address x.x.x.35

access-list 101 permit ip 192.168.5.0 0.0.0.255 172.16.5.0 0.0.0.255

ip nat inside source list 101 interface loopback10 overload

Obviously in your crypto map access-list you need to use the Natted address ie.

access-list 102 permit ip host x.x.x.35 172.16.5.0 0.0.0.255

HTH

Jon

Community Member

Re: 1841 to 3030 IPSec tunnel, no connectivity

Jon, thanks very much for your post! The problem I run into (I tried creating a virtual interface before) is that the two interfaces are now on the same subnet, which the router doesn't like.

So Fast0/0 is xx.xx.xx.34 and Loopback10 is xx.xx.xx.35. Which clearly won't work. And I can't define a sub-interface on FE0/0 that isn't ISL or similar trunking.

Is there a way to get around the IP address conflict?

Hall of Fame Super Blue

Re: 1841 to 3030 IPSec tunnel, no connectivity

Hi

router(config)# ip nat pool NATPOOL prefix-length 32

router(config-ipnat-pool)# address x.x.x.35 x.x.x.35

ip nat inside source list 101 pool NATPOOL

HTH

Jon

Community Member

Re: 1841 to 3030 IPSec tunnel, no connectivity

Jon, thank you very much for your help. The tunnel is up and talking, I really appreciate your assistance.

-Sean

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