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New Member

Intermittent internet connectivity- ?PIX

Hi there, I've got a bit of a problem, hoping someone can help with troubleshooting.

We have a site with 50 or 60 workstations, all connected via a PIX 515e to a DSL line, and thus to the web. Intermittently, and seemingly randomly, workstations lose the ability to web browse.

Sometimes, after a period of time, they regain their ability.

Checking I've managed to do thus far involves pinging the gateway address and doing some nslookups to see what the boxes can see. Ping works okay, nslookup always fails.

The workstations are all configured correctly. Nothing changes on them, they just lose browsing ability. I'm starting to wonder if its the PIX, although nothing has really changed on its configuration. (Alternately, its the new version of Panda antivirus, which quietly installs a scanning web proxy on each client, but Panda are denying any responsibility.)

Does anyone have any ideas what I could check on the PIX while the problem is happening? I've tried some 'show arp' stuff to see if there's arp resolution, and that's okay, the ip of the affected machine is listed.

The PIX has an unlimited licence, so I dont think it should be denying connectins for any reason I can see.

If anyone can help, I'd appreciate it.

thank you-


New Member

Re: Intermittent internet connectivity- ?PIX

As I said in another post, we saw a similar problem in the past. The PIX was not the culprit, but an ADSL router in front of it. The ADSL router did not let pass the packages with source port over 60000 or so. Is you have PAT configured on the PIX, this will be the case after some time running.

Check the traffic at the output interface in order to verify that the PIX is working fine. Then, check the traffic outside the router (trying to access a web server you possess) to see if the packets are transversing the DSL router.

Hope this helps. Regards.

New Member

Re: Intermittent internet connectivity- ?PIX

Jose, thats brillian, I'll have a look for your other post.

Yes, we are using PAT on the PIX, and there's a 1721 ADSL behind it. I take it that, after time, higher and higher port numbers are chosen, until eventually the 1721 cannot cope?

I've just found your other posts- how did you manage to resolve the issue? Clear xlate will knock the port counter back to zero, but wont the problem recur?

many thanks-


New Member

Re: Intermittent internet connectivity- ?PIX

Yes, the PIX uses higher and higher ports until it reach those that the router can not cope with.

We updated the software on the router. This behavoir is due to a software bug, but our router was not made by Cisco (it wes a SpeedStream by Efficient Networks).

Anyway, hope it helps.