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Old 05-31-2007, 03:11 PM   #1
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Registered: Jun 2005
Distribution: Mandriva
Posts: 4

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CentOS DNS fails on internal network (works on server)

CISCO --- CentOS ----- WinXP machine
_____ . . . . . . . . ________
eth0 ---- ***** ----- eth1

Hi everyone... two of us have been beating our heads against the wall and can't figure this out, so I hope someone can help.

I'm using webmin to configure all the settings.

The Server (CentOS4) has two NICs, one connected to a cisco router and the other to the internal network. It is doing NAT translation.

What works:
Server can connect and browse the internet without any issues. DNS lookup works great.
DHCP is serving ip,subnet,gateway, and all 3 dns server ip's properly to the client (winxp box at this time).
Client can browse the web using the IP address (google, ipchicken, whatever), but dns fails.
Client can use the IP to get to google, and perform a search, which works fine. Clicking a link fails because of DNS failure.
Client can ping the DNS servers fine.
Client can see and interact with the internal network, and with apache on the server perfectly.

What fails:
Client cannot use any name to connect outbound, DNS lookup fails.
On WinXP client, nslookup command fails to find the name of the dns servers and times out after 2 seconds.

The Server does not have BIND DNS installed because our ISP provides great DNS service, saw no need to add to the confusion.

We are baffled as to why DNS works at the server, nat traversal works at the client, but dns lookup is not passing along.


Some screenshots:

-Andy Lurig (ignore my sig, it is out of date)
Old 05-31-2007, 03:36 PM   #2
LQ Newbie
Registered: Jun 2005
Distribution: Mandriva
Posts: 4

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Yeah... Firewall was blocking. Had to add a rule, ACCEPT UDP 53.


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