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Using Windows XP and Cisco VPN client version 5.0.4.xxx to connect to a remote customer site. We are able to establish the connection and start an RDP session, but within 1-2 minutes the connection drops and the VPN connection disconnects. The PC making the connection is on a DMZ which is NATed to a public IP address.

If we move the PC directly onto the internet without being on the DMZ the connection works and we don't encounter any disconnects. We use a PIX 515E running 7.2.4 and don't have any problems with similar setups connecting to other customer sites from the DMZ.

The VPN setup on the client side is pretty basic, using IPSec over TCP port 10000. Not sure what device they are using on the peer, but my guess would be an ASA.

Any idea as to what the problem would be? Below is the logs from the VPN client when the problem occurs. The real IP address has been changed to: RemotePeerIP.

4 14:39:30.593 09/23/09 Sev=Info/4 CM/0x63100024 Attempt connection with server "RemotePeerIP"

5 14:39:30.593 09/23/09 Sev=Info/6 CM/0x6310002F Allocated local TCP port 1942 for TCP connection.

6 14:39:30.796 09/23/09 Sev=Info/4 IPSEC/0x63700008 IPSec driver successfully started

7 14:39:30.796 09/23/09 Sev=Info/4 IPSEC/0x63700014 Deleted all keys

8 14:39:30.796 09/23/09 Sev=Info/6 IPSEC/0x6370002C Sent 256 packets, 0 were fragmented.

9 14:39:30.796 09/23/09 Sev=Info/6 IPSEC/0x63700020 TCP SYN sent to RemotePeerIP, src port 1942, dst port 10000

10 14:39:30.796 09/23/09 Sev=Info/6 IPSEC/0x6370001C TCP SYN-ACK received from RemotePeerIP, src port 10000, dst port 1942

11 14:39:30.796 09/23/09 Sev=Info/6 IPSEC/0x63700021 TCP ACK sent to RemotePeerIP, src port 1942, dst port 10000

12 14:39:30.796 09/23/09 Sev=Warning/3 IPSEC/0xA370001C Bad cTCP trailer, Rsvd 26984, Magic# 63697672h, trailer len 101, MajorVer 13, MinorVer 10

13 14:39:30.796 09/23/09 Sev=Info/4 CM/0x63100029 TCP connection established on port 10000 with server "RemotePeerIP"

14 14:39:31.296 09/23/09 Sev=Info/4 CM/0x63100024 Attempt connection with server "RemotePeerIP"

15 14:39:31.296 09/23/09 Sev=Info/6 IKE/0x6300003B Attempting to establish a connection with RemotePeerIP.

16 14:39:31.296 09/23/09 Sev=Info/4 IKE/0x63000013 SENDING >>> ISAKMP OAK AG (SA, KE, NON, ID, VID(Xauth), VID(dpd), VID(Frag), VID(Unity)) to RemotePeerIP

17 14:39:36.296 09/23/09 Sev=Info/4 IKE/0x63000021 Retransmitting last packet!

18 14:39:36.296 09/23/09 Sev=Info/4 IKE/0x63000013 SENDING >>> ISAKMP OAK AG (Retransmission) to RemotePeerIP

19 14:39:41.296 09/23/09 Sev=Info/4 IKE/0x63000021 Retransmitting last packet!

20 14:39:41.296 09/23/09 Sev=Info/4 IKE/0x63000013 SENDING >>> ISAKMP OAK AG (Retransmission) to RemotePeerIP

21 14:39:46.296 09/23/09 Sev=Info/4 IKE/0x63000021 Retransmitting last packet!

22 14:39:46.296 09/23/09 Sev=Info/4 IKE/0x63000013 SENDING >>> ISAKMP OAK AG (Retransmission) to RemotePeerIP

23 14:39:51.328 09/23/09 Sev=Info/4 IKE/0x63000017 Marking IKE SA for deletion (I_Cookie=AEFC3FFF0405BBD6 R_Cookie=0000000000000000) reason = DEL_REASON_PEER_NOT_RESPONDING

24 14:39:51.828 09/23/09 Sev=Info/4 IKE/0x6300004B Discarding IKE SA negotiation (I_Cookie=AEFC3FFF0405BBD6 R_Cookie=0000000000000000) reason = DEL_REASON_PEER_NOT_RESPONDING

25 14:39:51.828 09/23/09 Sev=Info/4 CM/0x63100014 Unable to establish Phase 1 SA with server "RemotePeerIP" because of "DEL_REASON_PEER_NOT_RESPONDING"

26 14:39:51.828 09/23/09 Sev=Info/5 CM/0x63100025 Initializing CVPNDrv

27 14:39:51.828 09/23/09 Sev=Info/4 CM/0x6310002D Resetting TCP connection on port 10000

28 14:39:51.828 09/23/09 Sev=Info/6 CM/0x63100030 Removed local TCP port 1942 for TCP connection.

29 14:39:51.828 09/23/09 Sev=Info/6 CM/0x63100046 Set tunnel established flag in registry to 0.

30 14:39:51.828 09/23/09 Sev=Info/4 IKE/0x63000001 IKE received signal to terminate VPN connection

31 14:39:52.328 09/23/09 Sev=Info/6 IPSEC/0x63700023 TCP RST sent to RemotePeerIP, src port 1942, dst port 10000

32 14:39:52.328 09/23/09 Sev=Info/4 IPSEC/0x63700014 Deleted all keys

33 14:39:52.328 09/23/09 Sev=Info/4 IPSEC/0x63700014 Deleted all keys

34 14:39:52.328 09/23/09 Sev=Info/4 IPSEC/0x63700014 Deleted all keys

35 14:39:52.328 09/23/09 Sev=Info/4 IPSEC/0x6370000A IPSec driver successfully stopped

Thank you for any help you can provide.

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Are you seeing any drops in your firewall log the corresponds to the time that this connection drops? –  Zypher Nov 12 '09 at 17:52
    
Nope, nothing in the firewall log on our end that indicates a problem. –  IT Team Nov 18 '09 at 14:06
    
we have the same issue with my employer. and worse, the vpn will drop and not reconnect automatically! what we are doing now is testing a few units with openvpn, which has been a much better experience thus far. –  Peter Carrero Jun 3 '10 at 11:44
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2 Answers

I know this isn't much about explaining why, but I and (IT Helpdesk of the company) have found 4.x version much better what comes to Cisco VPN disconnections (especially if you use F-Secure firewall). So we always recommend people to change to older version. If someone knows the real reason why and how to configure the firewall with 5.x version, would like to hear the solution.

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Check your firewall logs, and also it's resource usage, it it's overloaded it won't be able to route traffic. Causing the timeouts your are experiencing. Also check the interface stats on the firewall and switches that connect you to firewall/internet. If you loosing packets because of bad cable, you'll have problems.

This really does look the firewall is closing ports, look for timeout setting on the firewall.

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