Cisco ASA IPSec tunnel how to find host using tunnel

jac1991
jac1991 used Ask the Experts™
on
Inherited a Cisco ASA and I have an IPSec tunnel configured and working great, however, I am trying to figure out which hosts are using this tunnel

Since the tunnel is encrypted, I can not seem to capture any packets

I see the peer ip for the tunnel, and the destination being the outside public ip of the ASA,  it need to the the host that is initiating this tunnel

Appreciate any insights, thanks
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Distinguished Expert 2017

Commented:
Check what the IPSec tunnel secures
Access on local side, what is it authorized to access on the remote side.
Look at the access list.
Show crypto IPSec sa
Show crypto iskmap

Interesting traffic, source,p/destination that will be permitted to enter the tunnel
Check the Nat rules presumably you are not excluding VPN traffic from being controlled by access-list (nonat) at which point, the only option you have is to debug the IPSec tunnel based on the remote destination to identify the source IPs/ports entering the tunnel
service ports represent responses, ports >1024 represent requests originating from your side.
Please note traffic entering the tunnel based on interesting traffic might not be allowed through on the other end.
You could reverse the filter to debug inbound based on source from the remote side.
Destination port >1024 is a response, service port a request.
Pete LongTechnical Consultant

Commented:
>>Since the tunnel is encrypted, I can not seem to capture any packets

If you capture the traffic 'incoming' into the inside interface, it wont be encrypted?
capture capout interface inside match tcp {inside LAN} {Peer-VPN LAN] 

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leave it running a while then
show capture capout

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Pete

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