How to monitor the traffic and systems in a site to site vpn

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Mar 16th, 2006
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I have a site to site vpn established between branch office and central office using Cisco PIX 515E at both ends

We have a dedicated link between offices, with vpn traffic routed to the dedicated link .

I see a high bandwidth usage in (both incoming and outgoing) in the link. how could I pin point which systems are sending and receiving traffic in VPN.

I have to identify the systems which are sending the traffic to the VPN



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Overall Rating: 4 (1 ratings)
jackko Thu, 03/16/2006 - 15:21
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in order to analyse the traffic within a vpn, the only way is to "get in" after the packets are decrypted.

one way i can think of is to use a sniffer straight connects to the pix inside interface.

another way is to do the sniffer on the pix, which involves a little bit complicated configuration.

in brief:

disable the command "sysopt connection permit-ipsec";

divide the subnet up to several sub-groups, configure inbound acl for individual sub-group in order to permit vpn traffic;

study the hit count of the acl;

re-create sub-groups based on the number of hit count e.g. a particular sub-group may be further divided providing most of the traffic are generated in this group; on the other hand, several sub-groups may be combined into a single sub-group providing not much traffic are generated by these groups;

repeat the re-group until the most "heavy" user/host/ip is identified.

jackko Fri, 03/17/2006 - 07:52
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it's good to learn that the information provided is valuable.

according to cisco,

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csaravanan Fri, 03/17/2006 - 10:53
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Hi Jackko,

Thanks for reminding me. I have rated your previous post



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