Can't telnet any longer to router via port 23 once again

[John Cheetley]

Evening techs,

Can no longer telnet to router again from windows server 192.168.0.102. Was connected 4 days ago OK no problem

C:\Users\Administrator>telnet 192.168.0.12

Can telnet to switch OK on ip of 192.168.0.2

Error of :
Connecting To 192.168.0.12...Could not open connection to the host, on port 23:
Connect failed

Troubleshooting done

Have disabled and re-enabled telnet via services.msc

Have un-installed/re-installed telnet client/server

Firewall is off.

C:\Users\Administrator>tlntadmn \\thebeast config port=23
The settings were successfully updated.

C:\Users\Administrator>ping 192.168.0.12

Pinging 192.168.0.12 with 32 bytes of data:
Reply from 192.168.0.12: bytes=32 time<1ms TTL=64
Reply from 192.168.0.12: bytes=32 time<1ms TTL=64
Reply from 192.168.0.12: bytes=32 time<1ms TTL=64
Reply from 192.168.0.12: bytes=32 time<1ms TTL=64

Ping statistics for 192.168.0.12:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

C:\Users\Administrator>tracert 192.168.0.12

Tracing route to 192.168.0.12 over a maximum of 30 hops

1 <1 ms <1 ms <1 ms 192.168.0.12

Trace complete.

netstat -a

Active Connections

Proto Local Address Foreign Address State
TCP 0.0.0.0:23 TheBeast:0 LISTENING

Is there a way that we can see what telnet is doing?

[John Cheetley]

Thanks Deepak, 

Will do this tonight. 

[John Cheetley]

Hi Deepak,

Sorry for my delay in getting back to you for this issue.

At the moment I can't telnet to 192.168.0.12 from 192.168.0.102

Can ping and tracert OK

netstat -ab | more shows listening on port 23 and firewall is off.

On the switch side. 192.168.0.2. (trunkport via port 24)

These are the results..

Switch#traceroute 192.168.0.12

Type escape sequence to abort.
Tracing the route to 192.168.0.12

1 192.168.0.102 1002 msec
192.168.0.12 5 msec 5 msec
Switch#ping 192.168.0.12

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.12, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/812/1049 ms
Switch#telnet 192.168.0.12
Trying 192.168.0.12 ...
% Connection timed out; remote host not responding

Switch#

Switch#show ip arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.0.0.1 - 0002.4b5d.01c0 ARPA VLAN2
Internet 192.168.0.102 0 fcaa.14af.197f ARPA VLAN1
Internet 192.168.0.2 - 0002.4b5d.01c0 ARPA VLAN1
Switch#

I'm am really no longer liking telnet.. It is so finnicky..

Thanks again for your help Deepak. I will soon be implementing ahmedshoaibs comments once I can reconnect to the router..

[Richard Burts]

Your results show very clearly that the problem is not lack of connectivity. So there is something on the device that sometimes does allow telnet and sometimes does not. I do not see any response to my suggestion that the problem is that the vty sessions all become busy and will not accept a new connection until the sessions are cleared (either by a timeout of the session, or by clearing some sessions, or by rebooting). Or any response to my suggestion that you configure a reasonable exec-timeout on the vty ports.

In this case it is not telnet being finicky. If you enable SSH you would have exactly the same issue.

HTH

Rick

[John Cheetley]

Hi Richard, 

Thanks for your response. I let my router alone for 4 days to let the exec-timeout command die out. I got access again last night. Followed your suggestions to reduce the timeout time frame..and nulled out other vty's that weren't necessary to make things simple.

Thanks again for your help. Much appreciated. Cisco is challenging at times

When I get home tonight will be putting amhedshoaibs feedback into action..

[Richard Burts]

Thanks for the update. I am glad to know that after 4 days that you were able to gain access again. That does seem to indicate that the fundamental problem was the exec timeout.

While there are reasons why most of us now prefer SSH over telnet, actions in this situation would be exactly the same.

HTH

Rick 

[John Cheetley]

Hi Richard,

I seem to be having the same trouble again with telnet.

Had access to router for 1 week but have now lost it again.

Error message is ..

Switch#telnet 192.168.0.12
Trying 192.168.0.12 ...
% Connection timed out; remote host not responding

Am attempting to connect from switch (192.168.0.2) to 192.168.0.12. Router on a stick setup

Can ping and traceroute to 192.168.0.12 OK

Firewall is off and router has port 23 enabled. 

Thanks in advance again...:) :) 

[John Cheetley]

Hi Richard,

This is output from switch ...

C:\Users\Administrator>netstat -abnop TCP

Active Connections

Proto Local Address Foreign Address State PID
TCP 0.0.0.0:21 0.0.0.0:0 LISTENING 1608
[FileZilla Server.exe]
TCP 0.0.0.0:23 0.0.0.0:0 LISTENING 1172
[tlntsvr.exe]
TCP 0.0.0.0:88 0.0.0.0:0 LISTENING 496

I have enabled port forwarding on gateway for port 23 to router

Below is output from switch command line

Switch#sh ip arp
ProtocolAddress Age (min) Hardware Addr Type Interface
Internet 10.0.0.1 - 0002.4b5d.01c0 ARPA VLAN2
Internet 192.168.0.102 0 fcaa.14af.197f ARPA VLAN1
Internet 192.168.0.12 0 000c.2915.4054 ARPA VLAN1 (router address)
Internet 192.168.0.2 - 0002.4b5d.01c0 ARPA VLAN1
Switch#telnet 192.168.0.12
Trying 192.168.0.12 ...
% Connection timed out; remote host not responding

Switch#

HTH.. 

[Richard Burts]

Sorry to hear that the problem has come back. My guess is that it is still an issue with configuration of the inactivity timer (or of disabling the inactivity timer) on the router. Can you post the section of the router config for line vry? Also please post from the router the output of the command show line

HTH

Rick

[John Cheetley]

Hi Richard,

line con 0
exec-timeout 15 0
password xxxxxxxxxx
login local
line aux 0
password xxxxxx
login local
line vty 0 4
exec-timeout 1440 0
password xxxxxxxxx
login local
transport input telnet ssh

And sh line attached..

HTH...

[Richard Burts]

Thanks for posting the information. I am a bit puzzled. Earlier posts in this thread show vty to be from 0 to 15 but now vty are 0 to 4. Has something changed? Is this the same router or a different one?

The output of show line is surprising. Previous posts in this thread had pretty clearly been an issue with inactivity timeout and I expected to find that the vty lines were busy. But this output indicates that there have been no successful access to the vty since the router booted. Can you post the output of show version so we can see how long a period that has been?

If there have been no successful access to the vty then it suggests that either something in the configuration or something in the operation of the router may be preventing the attempts at remote access. Is logging buffered enabled on this router? Is so would you check in the logs and see if there are any unexpected log messages?

Perhaps a more complete post of the router config might show us some issue.

HTH

Rick

[John Cheetley]

Thanks Richard for the reply.

Yes. Thats the only change. Same router as before.

Logging buffered not enabled

I can send router config tonight.

[Richard Burts]

Thanks for the response. Interesting that it is the same router. I am curious about how you got that router to go from vty 0 through 15 to vty 0 through 4. Seeing the config may help me to understand that.

Unfortunate that logging buffered is not enabled. I suggest that you enable it and then attempt remote access and then check what may show up in the logs.

HTH

Rick

[John Cheetley]

Will enable logging buffered and post config tonight..

[John Cheetley]

Hi Richard,

I now have telnet access to router

I got access via console cable to aux port and HT. Then telnetted to router via CLI.

That was yesterday.

Tried to connect directly via CLI using telnet and connection timed out. remote host not responding. Checked logs and nothing re telnet connection errors. 

But also shows 11 messages dropped. Maybe the memory isn't big enough.

I have connection again via console then opened telnet connection again.

I have checked the 192.168.0.1 internet g/w to ISP and it does have the port 23 open for telnet. Same for TFTP port once I get that setup.Further update coming..

Thanks again :) :) 

[Richard Burts]

I am glad that you have console/aux port access to the router. If I am understanding correctly you are successful in attempts to telnet to the router from the console session (which I would expect to work) but still not able to telnet to the router from the switch. Please post the output of show interface from the router and post the output of show arp from the switch.

HTH

Rick