Hi there,
I run a SunFire v245 with solaris 10. I run a custom ERP on that. my clients are connecting via telnet and run the application...

my last "server" was a sun blade 100 with solaris 8, everything was running correctly.

Since I have the new server, I have many problem with my clients. A lot of them have their telnet session closed by themself. I have start trouble shooting this problem and on client that disconnect themself, I've saw I can't ping the server anymore for few second and it come back few second after.

during the time I can't ping, other client can work without problem....

any idea of what looking for ?

Well, maybe not directly what you want, but: Have you tried ssh? Why don't you use ssh? If it's a productive ERP users would maybe be highly disappointed if the knew their company's ressources can be sniffed out by everybody.

I am using SSH on Solaris 9 & 10 without any problems (never used telnet)

have you tried to patch the system? is it maybe a autoneg problem with your switch (try to use forced datarates...)?
and yes, ssh is a better solution anyway... but if it is a networkproblem (and the ping thing looks exactly something like this) this won't be the solution to you problem...

ssh hang also...

Welcome to the club.
I also have a Sunfire 245 with similar problem.
Telnet clients "hangup" from time to time - during the hang-up period I can
still ping their devices from the Server as well as print to networked printers
if attched to their terminals. The "snoop" command does not log any data
sent from the telnet session ( does log the ping session ) - the telnet session may wake-up after a while - normally the client powers the unit off/on.
Some clients have also reported telnet time-outs - may only happen after
x hours - most clients are fairly busy so still need to test.
Strangely I do not have problems with sessions connected directly on the Lan , only remote clients.
To overcome the problem I have made the clients telnet to my original Data General Server , then automatically rlogin them onto the Sun server.
This is only a temp solution till we can resolve the problem.
We also have a problem with delays in printing at times - have converted to CUPS which appears to have helped but not totally resolved the problem.
I think the "hang-up" and printing delays are related to the same problem.

Sun support have not offered any solutions as yet.
Best of luck - doogel