Re: queer dns access problem

From: Bill Tangren <bjt(at)usno.navy.mil>
Date: Wed Dec 12 2007 - 15:43:06 EST

>> -----Original Message-----
>
> Some ideas:
>
> Turn off firewalling if possible.
>
> Check default route
> # ip route list
> 10.212.166.0/24 dev eth0 proto kernel scope link src 10.212.166.26
> 169.254.0.0/16 dev eth0 scope link
> default via 10.212.166.1 dev eth0 <----!!!!
>
> correct if necessary.
>
> Check for UDP connectivity
>
> # nmap -PU -p53 DNS.SERVER.IP.ADDRESS
>
> # traceroute -U DNS.SERVER.IP.ADDRESS

OK, this is what is produced on the server that works:

---

[root@mach2 X11]# ip route list
169.254.0.0/16 dev eth0 scope link
10.0.0.0/8 dev eth0 proto kernel scope link src 10.1.5.58 default via 10.1.1.2 dev eth0

[root@mach2 ~]# nmap -PU -p53 10.1.1.6
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2007-12-12 15:33 EST Note: Host seems down. If it is really up, but blocking our ping probes, try -P0
Nmap run completed -- 1 IP address (0 hosts up) scanned in 2.054 seconds

[root@mach2 ~]# nmap -PU -p53 10.1.1.46
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2007-12-12 15:33 EST Interesting ports on aurora.timenet.usno.navy.mil (10.1.1.46): PORT STATE SERVICE
53/tcp open domain
MAC Address: 00:18:8B:38:28:97 (Unknown)

Nmap run completed -- 1 IP address (1 host up) scanned in 0.295 seconds

[root@mach2 ~]#

---

The server that doesn't looks like this:

---

[root@aa-cvs ~]# ip route list
169.254.0.0/16 dev eth0 scope link
10.0.0.0/8 dev eth0 proto kernel scope link src 10.1.5.58 default via 10.1.1.2 dev eth0

[root@aa-cvs ~]# nmap -PU -p53 10.1.1.6
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2007-12-12 15:33 EST Note: Host seems down. If it is really up, but blocking our ping probes, try -P0
Nmap run completed -- 1 IP address (0 hosts up) scanned in 2.054 seconds

[root@aa-cvs ~]# nmap -PU -p53 10.1.1.46 Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2007-12-12 15:33 EST Note: Host seems down. If it is really up, but blocking our ping probes, try -P0
Nmap run completed -- 1 IP address (0 hosts up) scanned in 2.049 seconds

[root@aa-cvs ~]#

---

The difference
>
> If either works then check for an access list on your DNS. Usually in
> named.conf

I am having this problem even if I change the name and IP number of the broken server to the unbroken one. Same problem.

I have now reinstalled the OS on the broken server, and it STILL is having problems. It has to be a hardware problem, but I can't figure out what it could be.

>
> Try a different switch port if possible.

I'll have to talk to the network guys about this.

>
> --
> Stephen Carville <scarville@landam.com>

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Received on Wed Dec 12 15:43:53 2007