Seem to be having a bit of a problem with skype-probe.
I have a PA-500 in Vwire mode behind a PIX FW, the customer wishes to block Skype traffic.
1. On the ACC the ammount of skype-probe traffic far exceedes any other traffic in terms of sessions
2. The ammount of bytes of skype-probe traffic is roughly in relation to the amount of skype bytes
3. When enabling a skype only block rule (still allowing skype-probe) the active session count sky rockets
The sessions that increase dramatically are from skype-probe these sessions go from a current 4,000 sessions to 50,000+ in a matter of under a minute until the skype block rule is disabled.
Any help and insight will be greatly appreciated
attached is screen shots of skype-probe session count for last hour
Please reference the "Controlling Skype" document in knowledge point from the support.paloaltonetworks.com support portal.
My understanding is that you need to allow skype-probe traffic through to establish a connection, and then block the actual skype traffic once the Skype client believes it has connected. This prevents Skype from going evasive, but it does create a confusing situation on the client where it appears to be connected successfully, yet calling does not actually work.
skype-robe is allowed in a rule.
The rule set look like this:
|Source Zone||Dest Zone||Source||Dest||Source User||Application||Service||Action|
|Trust||Untrust||any||any||Known Users||Various Apps (Incl skype-probe)||any||allow|
Before skype is disabled the session count for skype-proble is high, as soon as you deny skype on the PA the skype-probe sessions go through the roof, as said earlier from about 4k sessions to 40k sessions in seconds.
try setting the allow skype-probe rule before the block skype rule, this may help decrease the number of probe connections
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