Dropped Telnet connections

[jim]

I have 30 users accessing a TS server with Wyse Winterms

(3235LE's and 3125SE's). Users use a terminal emulator

(Kermit 95) to access an RS/6000 with a telnet connection.

The problem is that sporadically, without any rhyme or

reason, they lose their telnet connection and the emulator

closes. Not all users, not all at one time. Some users

never, others as much as 5 times in a day.

I have tried other emulators, I have tried setting all

servers involved to fixed 100Mb Full duplex connections

(instead of auto-negotiate), all without success.

At the suggestion of the Software folks that maintain the

RS/6000, I replaced the Cisco 2900xl switch with another

switch (I picked up at Linksys 24-port 10/100 switch at

CompUSA) and the problem has resolved. This makes absolutely NO sense to me,

since the Cisco switch management reports no significant

errors, and I tried resetting the firmware before I

changed it out.

Is this just a "switch gone bad" or is there something about this switch I don't know and should have done? (I'll admit to being a IOS neophyte.)

Now, since we have a total of 47 ports in use between two 24 port switches, with a possibility of expanding another 12-16 devices, I'd like some suggestions as to what switch to buy as a permanent replacement. Everything is currently on one Class C subnet, and we've never used any of the advanced features of the 2900. Do I really need a *managed* switch?

Thanks for your reply!

Jim

[Georg Pauwen]

Hello Jim,

Catalyst switches have a number of compatibility issues with certain NICs, you might want to check this document, it might explain the dropped TELNET connections:

Troubleshooting Cisco Catalyst Switches to NIC Compatibility Issues

http://www.cisco.com/warp/public/473/46.html#intro

It might also be a bug in the Cisco software, which version are you running (can you post the output of the command ´show version´?).

Regards,

Georg

[jjbine245]

Georg, I have the same problem as mentioned. The switch we are using are the C3550. IOS is 12.1(14). The NIC on one of the PCs that constantly have problems is a Intel 100Pro. We replaced a 3Comm.

Any suggestions.

[n.titchener]

I've had experience of these NIC issues as well. Compaq servers running Gig NICs (sorry no part number) are unable to negotiate duplex/speed settings when connected to 3550-48 switches. I always set the NIC to auto and the swicth to 1000/full.

[erhoehne]

Hi Jim,

What do you have your nic card duplex/speed settings set to? Also, what are the switch port duplex/speed settings set to?

[jjbine245]

erhoehne;

The PC nic (Intel) is set at 100full. The C3550 switch is also set at 100full.

I've heard that there may be problems with Cisco switches, so this weekend we are moving some folks over to a different brand.

[erhoehne]

Sounds like your switchports are configured correctly as far as duplex/speed settings go. However, I notice that you said 3550 switch on your last post and 2900xl in your first post. Which kind of switch is it? If it's a 2900xl, when was it purchased?

Thanks!

[jjbine245]

We have 3550-48 switches.

Thanks

Jim

[erhoehne]

I know your switchport interface counters looked good off the 3550, but did you happen to try another known good ethernet cable?

[jjbine245]

Yes

[erhoehne]

This is strange. It sounds like a faulty switch. You should RMA it. I bet a new one would work stellar for you!

[johutchins]

I have a client that just started having telnet drops on a server and switch he's been using for a while without issue.

Last Friday he started getting ping and telnet drops to his SCO unix and Dec Alpha machines. Everything else is running great.

He is connected directly to a Cat6509. He has tried another card. Same problem...