2 or more Win XP (IPSec/L2TP) -> Cisco Router (PAT) -> Microsoft RRAS

Unanswered Question
Aug 3rd, 2007

Hi everyone,

I have a Cisco router (1710) to provide Internet access to guests and for testing.

The router is configured to do PAT:

ip nat inside source list 1 interface Ethernet0 overload

I also activated NAT-T (I think :) ):

access-list 120 permit esp any any

access-list 120 permit udp any any eq non500-isakmp

access-list 120 permit udp any any eq isakmp

On the other end I have a Microsoft RRAS Server for remote access (IPSec/L2TP).

If I connect a client (XP) behind my router and start the RAS connection, everything works.

If I connect a second client (XP) and try to connect to the same RRAS it does not work.

What do I have to configure on the router to get this working?

THX in advance.

Best regards,


I have this problem too.
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I think multiple pptp sessions are not supported from behind a single PAT device which could be the reason you are not able to connect two or more clients simultaneously. Also check if you have opened following ports needed for NAT-T.

Outbound - source udp any, destination udp 4500.

Inbound - source udp 4500, destination udp any.


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