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Telnet, DHCP and static

Tapas Jha
Valued Contributor

Telnet, DHCP and static

Dear All,

I am facing one peculiar problem on Telnet from client PC.
We have DHCP and client gets IP from DHCP server. Users telnet to different server for differenet applications.

Suddenly strange problem started with few of PCs while telnet'ing to server. I have checked DNS, DHCP. I can ping, traceroute servers, gateways. Everythings seems fine.

Few PCs are not getting telnet connection. I have checked from netstat -a command and found that "connection established" is showing for that server on the PC, but no login prompt is coming and it is getting disconnected.

Below are few scenarios where telnet is happenning on same PC.

If i make that DHCP IP as static IP (same IP) then also telnet is not happenning.

If I give another static IP then it can able to telnet to server.

Even if I change that DHCP IP to another IP of same DHCP range(different IP not used by anyone)manually giving as static then it can telnet to server.

If I once again change the above as DHCP (then it will take the same IP which i have done as static) then also it can telnet to server.

Do you have any idea how to resolve this?

Regards
Tapas Jha
Tapas Jha
2 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: Telnet, DHCP and static

Hi

You said "If I give another static IP then it can able to telnet to server. "

So i would check if the Server has ALREADY a telnet session established and for some reason hanged and not ended properly, so terminating it would resolve your problem.

Or

Since changing the IP will resolve the problem, then check why these IPs has a problem in the server, maybe its been blocked .... or try to restart the server.

Good Luck !!!
Science for Everyone
Pieter 't Hart
Honored Contributor

Re: Telnet, DHCP and static

Does this occur with selected clients or selected servers?

The telnet server could be at it's maximum telnet connections (or maximum processes at all).
It could be a wrong subnet mask on the server.

Is it all clients then the dhcp-server scope may have accidentally been changed.
check scope, and dhcp options.

It may be that the telnet server does a reverse dns-lookup wich fails.
If using W2K3 dhcp server and active directory check who registers the client name in DNS. Is this the client or the dhcp server (check the security tab of the DNS entry).

DHCP behaves differently between different OS'es of the the clients, the telnet-server and the DHCP-server.
So please specify.