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indanet
n00b
Joined: 05 Sep 2004
Posts: 54
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 Posted: Mon Dec 27, 2004 7:35 pm Post subject: DNS resolution problems, Ethereal logs inside (SOLVED) |
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Hi everyone!
I'm experiencing strange problems on two gentoo boxes in my LAN. My computers can't resolve all hostnames.
Here's a little part of a successful name resolution (I simply opened heise.de in links):
| Code: | No. Time Source Destination Protocol Info
1 0.000000 192.168.168.10 192.168.168.1 DNS Standard query A www.heise.de
2 0.144024 192.168.168.1 192.168.168.10 DNS Standard query response A 193.99.144.71
3 0.145900 192.168.168.10 193.99.144.71 TCP 33976 > www [SYN] Seq=0 Ack=0 Win=5840 Len=0 MSS=1460 TSV=21124831 TSER=0 WS=2
[...] |
As you can see, in frame 1 my computer (192.168.168.10) queries the local nameserver (192.168.168.1, in fact a Draytek router) for the IP address of www.heise.de. The router responds immediately with frame 2, after which my computer starts to connect to the web server (frame 3)...
When I try to access google.de, this happens:
| Code: | No. Time Source Destination Protocol Info
1 0.000000 192.168.168.10 192.168.168.1 DNS Standard query A www.google.de
2 0.067608 217.237.150.141 192.168.168.10 DNS Standard query response CNAME www.google.com CNAME www.google.akadns.net A 66.102.9.104 A 66.102.9.99
3 0.067681 192.168.168.10 217.237.150.141 ICMP Destination unreachable
4 5.000348 192.168.168.10 192.168.168.1 DNS Standard query A www.google.de
5 5.153641 217.237.150.141 192.168.168.10 DNS Standard query response CNAME www.google.com CNAME www.google.akadns.net A 216.239.59.99 A 216.239.59.104
6 5.153725 192.168.168.10 217.237.150.141 ICMP Destination unreachable
7 10.000738 192.168.168.10 192.168.168.1 DNS Standard query A www.google.de.homenetwork
8 10.202475 192.168.168.1 192.168.168.10 DNS Standard query response, No such name |
Frame 1: My computer queries the local nameserver for the IP of www.google.de
Frame 2: My local nameserver redirects the request to my ISP's nameserver, which answers my request.
Frame 3: My computer unexpectedly receives an DNS answer from my ISP's nameserver and drops it because it expected an answer from my local nameserver.
Frames 4-8: Two additional requests because the previous requests timed out (from my computer's point of view).
Kernel: gentoo-dev-sources
No firewall
LAN behind router (192.168.168.1)
An obvious solution would be to configure my computers to directly use the nameserver of my ISP because my router anyhow does forward all DNS requests to the "real" nameserver. The drawback of this solution would be that the IP of my ISP's nameserver is not as easy to remember as the IP of my router, and that the IP of the "real" nameserver can change. (The IP of the current nameserver is assigned to my router on dialup.)
So if you know a better solution than replacing the IP of my router with the IP of my ISP's nameserver in resolv.conf: Let me know...
Thanks in advance
chrschl
Last edited by indanet on Tue Dec 28, 2004 9:07 am; edited 1 time in total |
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NeddySeagoon
Administrator
Joined: 05 Jul 2003
Posts: 54821
Location: 56N 3W
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| Posted: Mon Dec 27, 2004 9:32 pm Post subject: |
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indanet,
Your router seems to be passing on 192.168... packets to your ISP, your ISP should really drop them because they are not routable. Instead the ISP nameserver responds directly to you. Thats two faults.
192.168.. packets should not leave your network.
If they do, they should be dropped at the next hop.
When you query your router for a name its doesn't have in its cache, it should ask upstream on its own behalf, add the response to its cache, then respond to the original query.
Is there a firmware update to your router?
_________________
Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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indanet
n00b
Joined: 05 Sep 2004
Posts: 54
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| Posted: Tue Dec 28, 2004 9:06 am Post subject: |
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| NeddySeagoon wrote: | | Is there a firmware update to your router? |
Thanks! That was it... |
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