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Here we have multiple servers which are running on different Operating systems, some are running on windows server 2003, red hat linux 4.0 and oracle unbreakable linux 4.

when we connect from client machine (which is running on windows XP) to servers running on linux using telnet it delays the connection for about 30 sec in showing login prompt.

But when we connect to servers which are running on windows, it connects immediatly .

this problem comes again and again and remains for about 10 to 15 days and then automatically get correct.

1 ) Why is this happening? 2 ) Is this a server problem or a network problem? 3 ) Explain in detail.

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1 Answer

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Could this be a DNS issue? Is there a reverse DNS record for the client machine? Servers commonly need to resolve the hostname of the connecting client machine to see if they're allowed to connect, as well as to log. Since the DNS lookup is synchronous, everything else will wait until the hostname is resolved, or it fails.

I suspect that the windows machines don't have the delay as they're resolving the reverse DNS of the clients either via WINS or Active Directory. Are the servers configured to resolve DNS from your Active Directory, if not, could you try configuring them to - otherwise, could you add a reverse DNS record for the client machines?

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we already have entered the ip and the hostname of server in client's host file. We don't use the active directory and DNS. and the configurations are same for all the servers. – Muahmmad Zeeshan Dec 31 '09 at 10:23
No, you need to enter the ip and hostname of the client in the servers hosts file. – petertonoli Dec 31 '09 at 11:17
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+1 - I agree. It sounds like the TELNET server isn't able to perform reliable reverse DNS lookups of the client IPs. – Evan Anderson Dec 31 '09 at 13:01
If you says that then why some times it works perfectly? – Muahmmad Zeeshan Jan 1 '10 at 5:44

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