Telnet sessions keep dropping

[Travis Paakki_1]

I know that a problem like this has a million possible causes, but I'm hoping somebody has had something similar so I can work from that.

I have a site that uses 900 Mhz RF Scanner guns via a Teklogix controller to log in via telnet to my server. At random points, these sessions seem to drop. At first I thought is was RF interferrance. But the same thing was happening to my LAN terminals running emulation.

The Teklogix controller was configured to hold the session open in the event of a loss of contact in case the gun went momentarily out of range a user would not loose their session, however, we only allow 1 login per id, so the glitch would resolve and the user could not get back in. I changed those settings but, as you would suspect, the problem keeps occuring. At least now the users can start from scratch after they get back on.

So here is where I'm stuck: What is causing these sessions to drop? I keep thinking it's a fault in the network (bad cable, switch, etc) although I can't find any records on the switches to indicate that. Others seem to want to blame the application that is running, but I don't see how an application could force a logout.

Any help in troubleshooting the issue would be greatly appreciated.

Thanks

[Steven E. Protter]

Check network connectivity and go from there.

On both sides run pings, and watch for large variances in response times.

In a good network you should not see that. Gradually rising ping times on HP NIC cards can indicate hardware trouble.

Next, run traceroute and see if there are any long delays on the route.

On the devices you are working with there is a possiblity of driver problems on the device.

If there is a router between you and the devices, it might need an ios upgrade.

Lastly, do you set TMEOUT and what do you set it to. That can shut inactive telnet sessoins.
P

[Niraj Kumar Verma]

try

# export TMOUT=0

-Niraj

[Steve Steel · Accepted solution]

Hi


TMOUT=0 is good


Also look at


ndd(1M) ndd(1M)

NAME
ndd - network tuning

SYNOPSIS
ndd -get network_device parameter

ndd -set network_device parameter value

ndd -h sup[ported]

ndd -h unsup[ported]

ndd -h [parameter]

ndd -c

DESCRIPTION
The ndd command allows the examination and modification of several
tunable parameters that affect networking operation and behavior. It
accepts arguments on the command line or may be run interactively.



For fine tuning


steve Steel

[rick jones]

If network problems are causing the telnet connections to drop, there will be "interesting" stats in the output of netstat -p tcp (ftp://ftp.cup.hp.com/dist/networking/briefs/annotated_netstat.txt)

If the cable connected to the NIC in the server is bad, you will see interesting things in the output of lanadmin -g mibstats for that link.

If the application quits, the session should still be there - of course, if the shell receives a ^D (aka EOF) over the telnet connection, the shell will go away - at least some shells that is. Unlikely, but a remote possibility I suppose.

[Travis Paakki_1]

OK,

After some extreme convincing (3 levels of mgmt involved) I was able to get a little further data and say the this was RFI. Cordless phones within the same band were stomping all over the telnet traffic.
The issue with the LAN terminals also "dropping" was actually more like they stopped responding. Reason: They were contending with a huge spike in network traffic as the RF guns tried to reconnect with the server.

Thanks so much for all of your efforts to assist.