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ISP Blocking Some VPN Traffic

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ISP Blocking Some VPN Traffic

Hi Everyone,

We are using an SA-4000 and recently upgraded fromNetwork Connect 5.3 to 6.1. Since the change one of our third party's can connect to the VPN OK but can no longer download certain binary files from the intranet, or access some secure internal sites. After a lot of investigation (connecting with different modem/router, from multiple machines and from other ISP's) we have found the issue is caused by the ISP he is using. The ISP have been able to replicate the issue and are investigating but don't seem to know what could be causing this.

When he is trying to connect to one particular site that always fails his NC.Service log starts repeating the following messages 

2008/05/28 17:43:09.256 dsNcService: t820 "DebugId" 'ipsec' [Debug] ipsec: Sending 212 bytes UDP to 202.14.181.123:4500
2008/05/28 17:43:09.256 dsNcService: t820 "DebugId" 'dsxp' [Debug] dsxp: WaitForMultipleObjects 6 handles for 5 secs
2008/05/28 17:43:09.364 dsNcService: t820 "DebugId" 'ipsec' [Debug] ipsec: Received 84 bytes UDP from 202.14.181.123:4500
2008/05/28 17:43:09.364 dsNcService: t820 "DebugId" 'ipsec' [Debug] ipsec: replay protection disabled
2008/05/28 17:43:09.364 dsNcService: t820 "DebugId" 'ipsec' [Debug] ipsec: replay protection disabled
2008/05/28 17:43:09.364 dsNcService: t820 "DebugId" 'adapter' [Debug] adapter: tun write IP packet len:40, ttl:126, prot:6, src:160.222.152.136, dst:160.222.251.18

This repeats about 20 times a second. We haven't noticed this on any of the clients that are successfully connecting. Does anyone have any idea what the ISP could be doing to cause this issue?

Thanks for any help!