Unable to telnet

Hi guys,

After changing my workstation from domain rsm.renesas.com to my.renesas.local, I was unable to telnet to 1 of our Sun Solaris servers.

There r errors in the messages file:
Aug 15 17:35:26 rsmsso1.svc.rsm.renesas.com inetd[24447]: [ID 140027 daemon.erro
r] warning: can't verify hostname: gethostbyname(vc00235.my.renesas.local) faile
d
Aug 15 17:35:26 rsmsso1.svc.rsm.renesas.com inetd[24447]: [ID 913506 daemon.warn
ing] refused connect from 172.16.101.120 (name/address mismatch)

Any ideas what it is? Thanks!

When you are logged onto the server, do an

nslookup 172.16.101.120 

to see what name it expects you to have. I am assuming your IP is 172.16.101.120.

What machine is this error log from?

Hi, thanks for the reply.

This error is from /var/adm/messages on the problematic sun solaris server.

root@rsmsso1.svc.rsm.renesas.com # nslookup 172.16.101.120
Server: w2ksrv30.rsm.renesas.com
Address: 172.16.101.240

Name: vc00235.my.renesas.local
Address: 172.16.101.120

Is that the same as your machine think it itself is?

Hi,

Previously, our workstation name is vc00235.rsm.renesas.com. However, our administrator changed the domain to vc00235.my.renesas.local. We r able to telnet to other sun servers, but only this 1.

We do not know why a domain changed in my workstation affects the telnet...

It looks like your system is setup so that telnet will refused the connection if it cannot validate the name.

What does /etc/nsswitch.conf say? It looks like gethostbyname() is not using DNS.

/etc/resolv.conf should be right otherwise nslookup would have failed.

Yea, really dun understand y..The resolv.conf n nsswitch.conf seems correct, they r the same as those telnet-able sun solaris server.

passwd: files
group: files
hosts: files dns
ipnodes: files
networks: files
protocols: files
rpc: files
ethers: files
netmasks: files
bootparams: files
publickey: files
# At present there isn't a 'files' backend for netgroup; the system will
# figure it out pretty quickly, and won't use netgroups at all.
netgroup: files
automount: files
aliases: files
services: files
sendmailvars: files
printers: user files

auth_attr: files
prof_attr: files
project: files

Thanks!

Not sure, have you solved it or not?

Is your IP or name listed in /etc/hosts?

You might have to try writing a small C program to call "gethostbyname" and "gethostbyaddr" to track this down to see why telnet is failing.

Problem is not solved yet. Still checking why it fails.

Can you ftp in?

Do you have a filter setup for telnet in /etc/inetd.conf?

telnet  stream  tcp6    nowait  root    /usr/sbin/in.telnetd    in.telnetd

Hi, we r unable to telnet n also ftp.

/etc/inetd.conf seems correct.

hi. this is behaviour by design in the server machine. What's happening is that the sun server that is not letting you in has a /etc/hosts.allow (and/or a /etc/hosts.deny) file that specifies rules telling it whether it should let a connection in depending on the connecting user/hosts/domain/network etc...

Normally, hosts.allow and hosts.deny are only checked when a program calls hosts_access(). By default, sshd and other programs do check the files, but not daemons like in.telnetd and ftpd, because these are services handled by inetd and by default inetd doesn't have tcp_wrappers on. The sysadmin must have enabled tcp_wrappers to telnet or to the whole of inetd, and thus each connection gets run through the /etc/hosts.allow and /etc/hosts.deny ruleset.

If you have a domain name change, maybe you are no longer making it through the rules in /etc/hosts.allow and /etc/hosts.deny so just update those.

Are you try to

nslookup 172.16.101.120
nslookup vc00235.my.renesas.local

on your server 1 ?

arm_naja