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cisco asa 5505 vpn tunnel *from* dmz *to* inside

Posted on 2011-02-13
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Last Modified: 2012-05-11
Before getting into the what's and why's of this config, is it possible to have  VPN tunnel originate from the dmz interface to a destination on the INSIDE interface?

I set the security level on dmz to 100 and enabled same-security inter/intra.  I enabled the isakmp policy on the inside interface, and have a route from the inside interface to the router to which the vpn should connect.

It seems that the traffic from the dmz is not considered interesting enough for the tunnel, as I get no crypto isakmp/ipsec debug info when I ping from the dmz host to the remote host.

Interestingly enough, if I ping from the remote host (see below), it will build a tunnel from the remote router to the ASA - the ping fails though (probably because the return traffic is not getting back into the tunnel on the ASA for the response).

I *can* ping from the ASA to the outside interface (192.168.100.10) on the remote router, so I know I can get traffic to/from a subnet that is different from the subnet on the inside interface.

ASA5505
inside: 192.168.1.202
dmz: 172.16.1.1
route 192.168.100.0/24 via 192.168.1.201 (another router on the inside)
crypto peer 192.168.100.10
dmz host: 172.16.1.10 (server)

Router 192.168.1.201
fa0/0: 192.168.1.201
serial1: 192.168.100.9/30 (p2p t1)

Remote Router
s1: 192.168.100.10/30
dmz. 172.16.4.1
dmz host: 172.16.4.10 (server)
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Question by:snowdog_2112
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3 Comments
 

Author Comment

by:snowdog_2112
ID: 34884430
Update: i can confirm that traffic from dmz destined for remote host connected via the inside interface gets sent out the outside interface.  A packet-trace shows this:

packet-trace in dmz 172.16.1.10  tcp 172.6.1.10 139 172.16.4.10 139 det

.
.
.
Phase: 2
Type: ROUTE-LOOKUP
Subtype: input
Result: ALLOW
Config:
Additional Information:
in   0.0.0.0         0.0.0.0         outside


Running the same trace to a host directly connected to the inside subnet, I get:

Phase: 2
Type: ROUTE-LOOKUP
Subtype: input
Result: ALLOW
Config:
Additional Information:
in   192.168.1.0     255.255.255.0   inside

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Accepted Solution

by:
lrmoore earned 2000 total points
ID: 34885322
Do you have a route statement on the asa:

route inside 172.16.4.0 255.255.255.0 192.168.1.201

On the local router is there a route statement:
 ip route 172.16.1.0 255.255.255.0 192.168.1.202

On the remote router is there a route statement:
 ip route 172.16.1.0 255.255.255.0 192.168.100.9

Otherwise, can you post your asa config?
What you are trying to do should be possible, but is not a typical implementation scenario
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Author Closing Comment

by:snowdog_2112
ID: 34889403
I actually had a post open to update with my success - but your answer is the one I discovered on my own.  You can have the points though since I did not update with my solution.

It should be noted that I do *NOT* need a route on the 192.168.1.201 router for the 172.16.x.0 subnets - the ASA only needs the route to force the traffic to the inside interface where crypto finds it "interesting" enough to tunnel.

Thanks!
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