Unable to telnet to a switch.

[shreecisco]

Hi to all...i'm a newcomer to this forum,

From PC, able to telnet to standby switch but unable to telnet to primary switch. Primary and standby switches are connected through uplink.

Ping response is positive from primary switch.Was able to telnet before. Suddenly, facing the said problem.

What could be the reasons?

Thanks,

Shreedhar.

[Richard Burts]

Shreedhar

If you can tell us a little more about the situation we might be better able to find an answer to your situation.

When you attempt to telnet do you get a prompt for username and/or password? If you do not get a prompt and the request is immediately denied then there are a couple of potential issues: perhaps the permit list on the switch has been changed and your address is no longer permitted.

Are other people able to telnet to the switch and just you are not able or is no one able to telnet to the switch? If no one is able then it would point to a different kind of problem on the switch.

What kind of error message do you get when you attempt to telnet? If the error is something about authentication failed then it indicates one kind of issue. But if the error message is something like connection refused by remote host it points to a different kind of issue.

Tell us a little more and we will see what we can find.

HTH

Rick

[peterledwidge]

Has any ACL been changed?

Did the switch reload and perhaps has lost part of it's configuration?

[shreecisco]

Hi,

When i try to access from PC,the message displayed is as follows:

Connecting To x.x.x.x...Could not open connection to the host, on port 23: Connect failed

From standby switch, when i telnet, this is the message displayed:

Trying x.x.x.x ...

% Connection refused by remote host

Only i have access to the L3 switches. And, i have not made any changes.

I hope i have made myself clear.

[Richard Burts]

Shreedhar

Is the switch in a situation where you could reboot the switch? If the switch reboots, do you still have the problem or does the reboot clear it up?

Do you have console access to the switch? If someone does have console access looking into the log file may have some clue as to what is going on.

What kind of switch is this?

HTH

Rick

[amit-singh]

Shree,

As been already pointed out by Kevin, there can be only 2 problems:

1 Switch has lost its config

2.Someone has changed the config or has applied ACL.

for 1, please do a show version and check the switchuptime.This will make sure if some has recently rebooted the switch and it has lost its config.

For 2, You have to consoled into switch just to see if its IP has been changed, its has lost its config or some one has applied the ACL's.

regards,

-amit singh

[peterledwidge]

Who's Kevin?

[b.orth]

Maybe all of the vty ports are hung.

Do you logout when you leave the switch?

HTH

[Josef Oduwo]

Peter,

Kevin is one of our resident gurus: http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Ddisplay_user_info%26location%3D.ee702b1&author=Kevin.Dorrell

Josef.

[sudeesh12]

......

[shreecisco]

Hi,

Thx guys for the inputs being given.But the problem persists.

On connecting to switch thru console, there is a debug arp command output being continously generated. Tried stopping it using 'undebug all' but unsuccessful.

Only i hv access to the L3 switch and i did not run the command.

Can it be a virus attack or some LAN card faulty?

Is there any other alternative other than rebooting the switch as it is a very critical one?

.

[stephenshaw]

Hi,

it's possible that the debug arp has driven up the CPU on the switch - if CPU gets too high it will prevent you from having telnet access.

Two things I would do ....

1. reboot the switch

2. find out who else has access to that switch and why debug was turned on and left on.

As previously suggested, someone may have changed the config on the switch.

Steve

[sebastian.wiegand]

Hi shree,

When u tried to turn off that debug.... where u in privileged mode? If not....Maybe it work this way... create a textfile with this contens:

en

"yourpassword"

un all

(2blank lines)

copy all of that to your clipboard(including the thwo blank lines) and when u are logged in, copy all of that to your Terminal application.

It might take a while until all messages are generated and the device is "silent".

And a little advice. Turn of the console logging on your machines by default. Use a Syslogserver or at least buffer the messages... So u are always able to log in(especially via con0), if sth like that happen again.

[noumanali26]

problem solved