unable to telnet

[DuKul]

Hi all,

I am facing strange situation - I cannot telnet to one HP-UX 11.23 system although:
1. I can login there by ssh or ftp with the same user
2. I can su -, or su to that user.

The telnet entry in inetd.conf is traditionally as follows:

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

When I am trying to seek inside of syslog on the target server during the telnet attempts I do not see nothing except that some telnet connection is trying to start:

Sep 24 15:10:50 saptest inetd[1041]: telnet/tcp: Connection from sapdbs1 (10.20.19.26) at Wed Sep 24 15:10:50 2008

Could you please give me some hints or guidlines what to check?

Thanks a lot.
Dukul

[J.G.D. van Zonneveld]

Hi,

Check de /etc/services file
telnet 23/tcp
and also check the /etc/hosts.allow and hosts.deney

[SKR_1]

Check for the following commands

1. more /etc/rc.config.d/netconf ( For default gateway )

2. /etc/resolv.conf

3. /etc/nsswitch.conf

4. nslookup server

Thanks

SKR

[DuKul]

Hi,

thanks for hints but:
1) I am not using hosts.allow, hosts.deny - i.e. if the daemon cannot find any of those files the access should be granted.
2) both servers have the same default gateway (they are on the same subnet)
3) nslookup works fine.

any other hints?

Dukul

[sreekanthtm]

Whats the error msg ur getting?
Is this an NIS user?
If the telnet prompt is getting hung for quiet long time then the issue could be with the DNS server. Check the /etc/resolv.conf and nsswitch. If u can post the content of these file.

[Ganesan R]

Hi,

You have not mentioned that the session seems to be hung or getting some errors. If the session looks hung or sometime takes very long time to give login prompt then it could be name resolution issue.

When we do the telnet to the server A from a client, Server A will do a reverse lookup(given an ip and find the host name) . This is a security protocol to make sure that the device trying to gain access is authorized.
There is no way to disable this feature. Sometime server will not be able to do reverse lookup. For example server is configured as DNS client and will not be able to access DNS server for some reasons(like DNS server down, Firewall inbetween, QZ zones, etc).Then there will be noticable delay to give the login prompt.

Resolution:

There are two ways we can resolve this issue. First one is we can include the clients in server hosts file. So that reverse lookup will happen locally. Make sure hosts is first lookup in /etc/nsswitch.conf.
Sometime it is very difficult to include all the clients in hosts file because we donâ t know from which clients the request will come. In that case include the following entries in /etc/resolv.conf file to sort out this issue like below. (retrans 500 and retry 2 )

# more /etc/resolv.conf
search
nameserver 10.176.0.3
nameserver 10.176.0.131
retrans 500
retry 2


Hope this helps you.

[Steven Schweda]

> [...] I cannot telnet [...]

> Whats the error msg ur getting?

> You have not mentioned that the session
> seems to be hung or getting some errors.

I assumed that his "L" key was broken. This
would explain why "ssh" and "su" both worked,
but "telnet" did not.

> Could you please give me some hints or
> guidlines what to check?

If you expect help from non-psychics, you
might explain what "I cannot telnet" actually
means.

[Gokul Chandola]

Dear Dukul,
Please use root user for login.
Try it, will work.

Regards,
Gokul Chandola

[DuKul]

Hi all,

sorry I did not specify that I don't get any error messages within the syslog; the only message I am getting is

login: d46adm
Password:
Login incorrect

and in syslog on the target:

Sep 25 09:09:35 saptest inetd[14600]: telnet/tcp: Connection from sapdbs1 (10.20.19.26) at Thu Sep 25 09:09:35 2008

and nothing more.

The names entries of both machines are same within hosts files on both servers, nslookup works fine, as I have already written.

The nsswitch.conf is setup as follows (and as needed for such case):

hosts: files [NOTFOUND=continue] dns

[Sushil Srivastava]

Kindly check with this way login to the server

#telnet localhost

and try to login by the same user name and password on both the servers.

Let me know waht error message comes