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Telnet through VPN connection keeps dropping

Posted on 2006-11-07
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Last Modified: 2013-11-16
We use a program called Tiny Term from Century Software, which uses Telnet through a VPN connection to connect to corporate servers in another state.  After users login using their account information, the connection is dropped after 2-5 minutes.  The time varies, and when it happens, ALL connections for this program stop.  By that, I mean each workstation running this program stops responding on every machine.

But not the Internet.  If I run a continuous ping from one station, login to Tiny Term, and monitor the progress of the ping, it never drops while the Telnet connection does.  This is a small store, and it is setup with the following:

DSL provided modem/router>Cisco Secure Pix 506>SMC Switch>Workstations (all running XP Pro)

This all started last week, and I have done the following:  Confirmed that network connectivity during this to the Internet does NOT go down.  Ran spyware scans and anti-virus scans.  Called corporate to check the firewall out, and was told traffic looked good.  Called the ISP to check their side out, and was told their side good.  Removed the SMC switch and replaced with another, left all workstations unplugged from new switch, and plugged in a newly setup workstation, never before on this network, with a fresh install of Tiny Term.

And still, it did the same thing.  Removing the switch and workstations would seem to me, to remove our internal network from the equation.  To me, it would seem to be some sort of setting within either the firewall or modem/router.  But what?

How would I monitor this type of program and the traffic that it generates, bearing in mind I do not have access to the firewall?  How would I monitor the connection when it drops?  What would I look for?  Any help would be greatly appreciated, as users are tired of constantly signing back in.

Thanks

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Question by:lloydr1l
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17 Comments
 
LVL 12

Expert Comment

by:Freya28
ID: 17890424
check all your timeouts on teh pix and especially the vpngroup idle-timeout
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Author Comment

by:lloydr1l
ID: 17890607
I will pass that along to corporate, as I can't personally check it.  
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Expert Comment

by:Freya28
ID: 17890652
i would most definitley say it is a timeout setting too low on the pix
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Author Comment

by:lloydr1l
ID: 17891347
I started thinking about your suggestion.  One of the things the ISP tech stated was that he connected to his office using VPN and the connection never dropped.  So wouldn't that then imply that any setting too low for vpngroup idle-timeout could be eliminated?  If it were to low, wouldn't it have effected his connection?
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Author Comment

by:lloydr1l
ID: 17891354
Just remembered him telling me he went around the firewall, so forget that.
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LVL 12

Expert Comment

by:Freya28
ID: 17891654
what about the actual program?  does that have a timeout?  or the application?
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Author Comment

by:lloydr1l
ID: 17891669
Nope.  There are no settings for this.
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LVL 12

Expert Comment

by:Freya28
ID: 17891736
i would also check the wan link.  see if it is hiccupping at all.  telnet is the simplest traffic to traverse, but if any type of break in the line occurs, then all connections will be dropped.
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Author Comment

by:lloydr1l
ID: 17893127
Freya28
Agreed, but how to check?  ISP claims the connection is fine.  Corporate claims the firewall is fine.  How do I monitor the WAN link and see if it is hiccupping?  
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LVL 12

Accepted Solution

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Freya28 earned 500 total points
ID: 17898121
There are many tools out there, but for a price.  you can sniff the network also with freeware such as etherreal or wireshark to see where packets are dropping.  i would try that.  sniff the network usign etherreal and identify the source IP and destination IP and follow the tcp stream.  it might give you a clue as to where it is dropping, then you can take it from there.
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Author Comment

by:lloydr1l
ID: 17899669
Thanks.  In fact, that is what I have been doing.  I've been looking into Wireshark for the last couple of hours.  As soon as I get comfortable with it, I will try it out.
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Expert Comment

by:Freya28
ID: 17899715
good,  let me know
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Author Comment

by:lloydr1l
ID: 17907594
I know how to read a lot of the captured output, but there are things I don't understand.  So do you know of a place where previous output has been analized?  With explainations of the results?
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LVL 12

Expert Comment

by:Freya28
ID: 17907713
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Author Comment

by:lloydr1l
ID: 17907749
Thanks.  I'll check it out.
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Author Comment

by:lloydr1l
ID: 18093787
Thanks for the help and sorry for the delay in rewarding points.  I never had a chance to follow through on this because I was redirected.  But I'm sure the suggestion you offered is the answer to finding a solution.
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Expert Comment

by:Freya28
ID: 18093811
thank you and good luck
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