what may be the causes, what should i do to telnet with a specific port.

well first you need to install a telnet server, in your telnet server configuration you tell the telnet server to listen to a specific port.

The easiest way to do things like this just for testing purposes is to use an realy old program called Netcat.

Then we have the small problem of firewalls, if the host has a software firewall you would need to configure it to let the desired ports through.

And of course all routing and firewall/nat issues. but that is a different question.

Are you performing any PAT or NAT between the switch and the remote devices?

What happens when you try and use port 23?

when i m trying with 23/80 it is ok, telnet is getting fine. but when i m trying with other ports its not happening..

OK - if 23/80 is working for your telnet, why are you trying different ports?

Are the devices you are trying to connect to using different ports actually "listening" for a telnet connection using that port?

yes, some application needs to connect through different ports, so I need to check the port is open or not.

The I would suggest that you check on the server itself if it is "listening" on that specific port number.

The "netstat" command works on Windows and Linux.

HTH.

there is a ping utility called slping.

It will ping on any port you specify. I uploaded the program once before, it is a .exe program.

Here is the link with instructions too.

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Service%20Providers&topic=VPN%20Service%20Architectures&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.2cbeb94e/7#selected_message

This will tell you if the device is open for any port number. If not then you will need to go to the server and do a netstat -a to see if the port is listening or established.