Telnet Connection Refused

[Mike Adams_1]

I have a A500 server that I can ping and/or trace to, but I cannot telnet to it from other devices on the LAN or telnet from it to other devices on the LAN. I have check my services file and inetd.conf and see no restrictions on telnet. Any ideas?

[Steve Labar]

Mike,
Verify that telnet is not listed in your /var/adm/inetd.sec

[Sanjay_6]

Hi,

If other users are able to login into this box using telnet, check and see if the systems is behind a firewall. If so you will need your ip to pass through the firewall.

Are all users unable to login using telnet?.

Hope this helps.

Regds

[Mike Adams_1]

No users can telnet to this server. From the console I can ping the default gateway, but I am unable to telnet to any other device. From Console I can telnet the back to the server I am on.

Telnet is not disallowed in inetd.sec

[Michael Tully]

From another session i.e. the console, verify that the 'inetd' process is actually running.

[Mike Adams_1]

inetd is running

[Michael Tully]

Hi,

The 'inetd' process is the process
that starts child 'telnetd' processes.
It could be that 'inetd' itself,
although still running has a problem.
Suggest killing it off from the
console and restarting it.

# inetd -k
# /sbin/init.d/inetd start

-Michael

[Darrell Allen]

Hi Mike,

I'm not sure I read your post correctly. Can you telnet from the server to itself? If so, then inetd and telnetd are not the problem.

If you can't telnet from the server to itself then I'd suspect inetd.sec, inetd, or telnetd. You could try sending a HUP signal to inetd (kill -HUP inetd_pid).

Re-reading your post now I wonder if your subnet mask is correct? If you are on the same subnet you should be able to ping, rlogin, telnet, whatever assuming inetd.sec does not deny that and inetd.conf has those services enabled.

Have you verified you routes?

Just some things to consider.

Darrell

[Mike Adams_1]

I can telnet from the server to itself. I have run a netstat -rv and the default route for the lan is correctly configured. Ping works intermittently from the server to other hosts on the lan, roughly 1/3 to 2/3 attempts.

This is very strange problem and I am completely out of guesses. Any suggestions are greatly appreciated.

[Mike Adams_1]

Forgot to mention that we have soft and hard restarted and replaced the NIC, all with no effect.

[Bill Hassell]

Since telnet from the problem machine works to itself, the problem is likely networking, in this case it may be DNS. (I'll assume that the telent error is something like connection closed by remote host) Eliminate DNS by renaming the /etc/resolv.conf file and put the IP address and name of a remote machine into /etc/hosts.

If telnet now allows a remote connection from this machine, your DNS server likely does not provide reverse lookup, something that is very important for a secure network. Telnet does validate that the remote system name has an associated IP address to avoid spoofed addresses.

[Mike Adams_1]

Bill,

Thanks for the suggestion. It's not a public network and we are not running DNS. I too think this is a networking issue, but I can't put my finger on the cause.

Any other ideas?

[Manoj Kumar Sarangi]

There are few things which are to be tested.
1. First check the /etc/services file,it should have an entryas the following.

telnet 23/tcp # Virtual Terminal Protocol

2. next is to check /etc/inetd.conf
It should have an entry like

telnet stream tcp nowait root /usr/lbin/telnetd telnetd

3. Pl. check whether the telnetd file exist at /usr/lbin/ directory

4. If you give a command

netstat -a|grep telnet

a line like mentioned below should indicate the 23 port is open.

tcp 0 0 *.telnet *.* LISTEN

5.If all these are okay check /etc/nsswitch.conf
It should have a entry like.

services: files [NOTFOUND=continue] nis

pl. note that files should precede nis if nis is present.

Pl. check this and let me know..If all these are okay I don't see a reason why it should not work.

Manoj

[Justo Exposito]

Hello Mike,

Perhaps is a hardware error, to check you can use lanscan to know the ppa and lanadmin to check and reset your lan card. You can use like this:
HP4 #> lanscan
Hardware Station Crd Hdw Net-Interface NM MAC HP-DLPI DLPI
Path Address In# State NamePPA ID Type Support Mjr#
0/0/0/0 0x00306E038957 0 UP lan0 snap0 1 ETHER Yes 119
1/12/0/0 0x00306E04703D 3 UP lan3 snap3 2 ETHER Yes 119
0/4/0/0 0x001083FBF880 1 UP lan1 snap1 3 ETHER Yes 119
0/5/0/0 0x001083FBC90B 2 UP lan2 snap2 4 ETHER Yes 119
HP4 #> lanadmin


LOCAL AREA NETWORK ONLINE ADMINISTRATION, Version 1.0
Tue , Nov 27,2001 10:18:06

Copyright 1994 Hewlett Packard Company.
All rights are reserved.

Test Selection mode.

lan = LAN Interface Administration
menu = Display this menu
quit = Terminate the Administration
terse = Do not display command menu
verbose = Display command menu

Enter command: lan

LAN Interface test mode. LAN Interface PPA Number = 0

clear = Clear statistics registers
display = Display LAN Interface status and statistics registers
end = End LAN Interface Administration, return to Test Selection
menu = Display this menu
ppa = PPA Number of the LAN Interface
quit = Terminate the Administration, return to shell
reset = Reset LAN Interface to execute its selftest
specific = Go to Driver specific menu

Enter command: ppa
Enter PPA Number. Currently 0: 0

LAN Interface test mode. LAN Interface PPA Number = 0

clear = Clear statistics registers
display = Display LAN Interface status and statistics registers
end = End LAN Interface Administration, return to Test Selection
menu = Display this menu
ppa = PPA Number of the LAN Interface
quit = Terminate the Administration, return to shell
reset = Reset LAN Interface to execute its selftest
specific = Go to Driver specific menu

Enter command: display

LAN INTERFACE STATUS DISPLAY
Tue , Nov 27,2001 10:18:22

PPA Number = 0
Description = lan0 Hewlett-Packard 10/100 TX Half-Duplex TT
= 1500
Type (value) = ethernet-csmacd(6)
MTU Size = 1500
Speed = 100000000
Station Address = 0x306e038957
Administration Status (value) = up(1)
Operation Status (value) = down(2)
Last Change = 1734
Inbound Octets = 0
Inbound Unicast Packets = 0
Inbound Non-Unicast Packets = 0
Inbound Discards = 0
Inbound Errors = 0
Inbound Unknown Protocols = 0
Outbound Octets = 410
Outbound Unicast Packets = 10
Outbound Non-Unicast Packets = 0
Outbound Discards = 0
Outbound Errors = 0
Outbound Queue Length = 0
Specific = 655367

Press to continue

and for last you can reset the lan card by using the reset option in the menu.

Hope this help,
Justo.

[Darrell Allen]

Hi Mike,

Okay, it's not a network service problem. Nor is it name resolution.

The key is ping is showing a problem so it could be several things:

NIC set to the wrong interface type (BNC, rj45, etc). I'd check this first.

Mismatch duplex setting between the server and the switch. I doubt this one since ping is erratic. Generally you don't see a problem until sending a lot og data over the net.

NIC is flaky. Doubtful since you've replace it.

Switch port is flaky. Try a different port.

Network cabling is flaky. Try a different cable.

Darrell

[Steve Labar]

It really seems that your system is running correctly. If ping is only working intermittently I would start looking at your network layer 1. Try pinging "localhost" and verify no packets get dropped. If localhost is dropping packets, the NIC could still be a problem. If localhost does not drop packets, then I would check cabling, hubs, switches, etc.

Steve

[Mike Adams_1]

Thank you all for your suggestions.

To close the loop I will share the story.

After much trial, we finally identified a duplicated IP address on the LAN. We still cannot identify the source, but we were able to re-address the nic on the server in question and all is now fine.

Thank you all.