My PC's IP address on Unix Server Appears Different with My Real IP

[morganelan]

Hi Unix Gurus,
My client Ip address is 10.213.2.107 but why on my Unix Server, it appears as 10.213.1.129.This ip is given by our windows dhcp server and on our Unix Server we do not configure dhcp but we have bootptab for jet direct configurations.How to find out which dhcp server that give this 10.234.1.129 ip address?But this is very strange if I login again it appears the correct ip again as 10.213.2.107.Any replies will be appreciated....

[RAC_1]

nslookup 10.234.1.129
nslookup "client_name"

Is it same?? How does hp-ux resolve the host names?? What it uses first?? Check /etc/nsswitch.conf file.

[morganelan]

Yes nslookup 10.213.1.129 return the same with nslookup Client-Name.This is my /etc/nsswitch.conf :

# more /etc/nsswitch.conf
# /etc/nsswitch.conf:
#
#hosts: files [NOTFOUND=continue] dns [NOTFOUND=return]
hosts: dns files

[Torsten.]

If your client is running windows, do a

ipconfig /all

(on the client)

for detailed information about DHCP.

[Arunvijai_4]

Do you have any IP masquerading software installed on client's machine ?

-Arun

[Nemer_1]

Hi,

this sounds like an incorrect entry in your DNS server. you need to remove this record from the DNS.

try to ping 10.213.2.107
is it reachable from the unix machine?

[Muthukumar_5]

what is in /etc/nsswitch.conf file for hosts: entry. Is there any entries in /etc/hosts file?

That may be a problem too. Check from unix machine as,

# nslookup 10.213.2.107
# nslookup 10.213.1.129

Post results.

hth.

[morganelan]

# nslookup 10.213.2.107
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.2.107"
#
# nslookup 10.213.1.129
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.1.129"

[Borislav Perkov]

Hi Morganelan,

Your PC DNS record is not accurate for both addresses or there is an old record of the current MAC address of your PC network card in DNS server or maybe in DHCP server database. You need to make changes on DNS server, maybe rebuilding the records or something like.

Regards,
Borislav

[VEL_1]

Hi,

Check your server & in firewall setting whether you have done any IP Masquerading.

Thanks.

[Nemer_1]

sorry what did you mean by :

"Yes nslookup 10.213.1.129 return the same with nslookup Client-Name"

in your first response & the nslookup results in the second response:

"# nslookup 10.213.2.107
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.2.107"
#
# nslookup 10.213.1.129
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.1.129"

As there in no hostname available in the DNS for 10.213.1.129

[Muthukumar_5]

what is your routing table entries?

netstat -rn
netstat -in

May be a problem with routing from windows -> unix or vice versa.

From windows-->

a) tracert 10.213.2.107
b) tracert 10.213.1.129

From Unix machine -->

a) traceroute

Post this information.

hth.

[morganelan]

Sorry, I have mistaken typing in the first reply.
If I do nslookup in windows client, it looks like this:
C:\>nslookup 10.213.1.129
Server: dnsserver.mycompany.com
Address: 10.213.0.61

*** dnsserver.mycompany.com can't find 10.213.1.129: Non-existent domain

C:\>nslookup client1
Server: dnsserver.mycompany.com
Address: 10.213.0.61

Name: client1.mycompany.com
Address: 10.213.1.129

If I do nslookup from my Unix Server, it looks like:
# nslookup 10.213.2.107
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.2.107"
#
# nslookup 10.213.1.129
Name Server: dnsserver.mycompany.com
Address: 10.213.0.61

Trying DNS
looking up FILES
*** No hostname information is available for "10.213.1.129"

[VEL_1]

Hi,

In Unix, use dmesg command & verify /var/log/messages.

Also refer the following link:

http://groups.google.com/group/mlist.linux.newbie/browse_thread/thread/66cc023018bcf092/ed9b83e46706aa66?lnk=st&q=DHCP+client+IP+Linux+log+dmesg&rnum=2&hl=en#ed9b83e46706aa66

[Muthukumar_5 · Accepted solution]

From windows:

host -> ip is resolving out. But reverse of ip-> host is resolving. It is because of dns reverse lookup setting.

From Unix:

It is not registered with dns. You have to register your unix machine ip-address / hosname with dns. Or else,

create /etc/hosts file as,

FQDN

Change /etc/nsswitch.conf -->

hosts: files dns

It will do host -> ip and ip-> host resolvation.

hth.

[Arunvijai_4]

Can you post your tracert and traceroute results ? Also, Are there any IP Masqueraders in your Firewall ?

-Arun

[morganelan]

Yes Nemer, you are right in /etc/hosts we don't have ip 10.213.2.107 and 10.213.1.129, because both come from our windows dns server.

[Muthukumar_5]

We usually use /etc/hosts or C:\Windows\system32\drivers\etc\hosts to update IP or hostame or FQDN. It is good to keep command hosts file to do forward lookup and reverse lookup.

Try to set up /etc/nsswitch.conf hosts: resolvation with files and then dns next.

hth.

[Nemer_1]

Hi,
is your DNS server is microsoft DNS server?

if yes...is your DHCP server setted to update the DNS server records??

it seems not...

[Muthukumar_5]

You are using only 10.213.0.61 as nameserver then try to update records in that. On getting update in dns records in 10.213.0.61, you can change resolvation of hosts: with /etc/resolv.conf as dns files. Before that to resolve this, you have to records in files of windows & unix. (Temporary solution to make nslookup to get success).

hth.

[morganelan]

Thanks all of you ......