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ping and telnet - HP-UX

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# 1  
Old 08-06-2010
ping and telnet - HP-UX
Hi all,

I am not sure if my problem is specific to HP-UX or not. Hopefully someone can tell me what's wrong.

I have a server name server1 10.100.50.10 in the /etc/hosts file and if I do a ping server1, it shows the right IP address.

However, if I run telnet server1, it is not using 10.100.50.10 but the one that is on the DNS server. Can someone please advise if this is the "normal" or expected behavior of telnet? Is there something that I have to do to force telnet to resolve the name using the /etc/hosts file first instead of the DNS server?

FYI, I checked the /etc/nsswitch.conf and I do not have uncommented entries there which means it is not used. I have the /etc/resolv.conf file but I presume that the order of name resolution is the /etc/hosts first and then /etc/resolv.conf, is this a wrong assumption?

Any advise will be very much appreciated. Thanks in advance.
# 2  
Old 08-06-2010
/etc/nsswitch.conf determines the order that various datasources that map names and IPs are used. If you don't have any uncommented entries in that, I suppose that means that whatever the system default happens to be is in use. Often, the commented entries show you what that default is.

I would try editing nsswitch.conf to have a line like this:

Code:
hosts: files dns

That should cause /etc/hosts to be used before a DNS lookup is performed.
# 3  
Old 08-07-2010
The default values are:
Code:
nsswitch.conf
hosts:          files
aliases:        files

If your nsswitch.conf is like this, it was not using DNS.


Please post:
The contents of:
Code:
/etc/nsswitch.conf
/etc/resolv.conf

And the response to:
Code:
nslookup server1
nslookup 10.100.50.10
egrep "server1|10\.100\.50\.10" /etc/hosts

Last edited by methyl; 08-07-2010 at 06:05 PM.. Reason: Misplaced CODE tags (third attempt)
# 4  
Old 08-11-2010
Hi methyl,

Thanks for your response. Requested output is as below.

Note that there are two telnet attempts below. The first is using the hostname and the second is using the IP address. I was expecting both to behave the same, i.e., use the /etc/hosts file entry but that does not seem to be happening.

The first telnet using the hostname is connecting via the DNS and the second telnet using the IP address is connecting via the /etc/hosts file. This is my assumption. I can tell that the first telnet is using the one from the DNS server because I don't see the HP-UX banner while the second telnet attempt is showing the HP-UX banner. The HP-UX server is the one that am wanting to connect to.


Code:
root@server2:(root)> cat /etc/nsswitch.conf
#
# /etc/nsswitch.files:
#
# An example file that could be copied over to /etc/nsswitch.conf; it
# does not use any name services.
#
hosts: files [NOTFOUND=continue UNAVAIL=continue TRYAGAIN=continue] dns
root@server2:(root)> cat /etc/resolv.conf
domain dev1.com.ph
search dev1.com.ph dev1.com.cn
nameserver 10.100.3.105
root@server2:(root)> nslookup server1
Using /etc/hosts on:  server2

looking up FILES
Name:    server1.dev1.com.ph
Address:  10.100.50.10
Aliases:  server1, server1.dev1.com.ph

root@server2:(root)> nslookup 10.100.50.10
Using /etc/hosts on:  server2

looking up FILES
Name:    server1.dev1.com.ph
Address:  10.100.50.10
Aliases:  server1, server1.dev1.com.ph

root@server2:(root)> egrep "server1|10\.100\.50\.10" /etc/hosts
10.100.50.10     server1.dev1.com.ph server1


root@server2:(root)> telnet server1
Trying...
Connected to server1.dev1.com.ph.
Escape character is '^]'.
Local flow control off
login: root
Password:
Not on system console
Connection closed by foreign host.
root@server2:(root)> telnet 10.100.50.10
Trying...
Connected to 10.100.50.10.
Escape character is '^]'.
Local flow control on
Telnet TERMINAL-SPEED option ON

HP-UX server1 B.11.23 U ia64 (ta)

login:

# 5  
Old 08-11-2010
The nslookup on "server2" looks ok to me. It's using /etc/hosts and getting an answer.

The problem could be on "server1" not recognising "server2" as a valid server in a secure environment depending on whether the "telnet" is by name or by IP address. This can be a reverse DNS lookup issue on the client or an access control setting ... or something else.

1) Need to ensure that the nslookup by name and IP address for both "server1" and "server2" are totally consistent on both "server1" and "server2".
Also try "telnet" from "server1" to "server2" by name and IP address.

2) Check /etc/hosts.allow and /etc/hosts.deny on "server1" and "server2".

3) If this is not a secure enviroment it might be due to the contents of /etc/securetty (if present) on "server1" but I don't think you get the "not on system console" message from HP-UX.
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