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mds1327's profile

Tutor

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5 Messages

Tue, Nov 22, 2016 4:12 PM

Router giving out incorrect DNS for internal IPs

Hi. I have an NVG589. I have several computers with various OS's connected to it (both wired and wireless) and a few of them have specific IPs allocated from the DHCP pool. The router allocates the IPs correctly, but it does not return the correct addresses to DNS. For example, I have computer 'foo' up and listening on 192.168.1.65 but the router's device page, and nslookup, tells me it's a 192.168.1.67.  Neither rebooting the router nor clearing the device list corrects the problem. Any thoughts?

ApexRon

Professor

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2.2K Messages

6 y前

DNS has nothing to do with your at home network other then tell your network devices how to connect to an IP network device that is not part of your at home IP network.

 

When I do a "man nslookup" from the terminal command line I get the following information:

"Mac OS X NOTICE
The nslookup command does not use the host name and address resolution
or the DNS query routing mechanisms used by other processes running on
Mac OS X. The results of name or address queries printed by nslookup
may differ from those found by other processes that use the Mac OS X
native name and address resolution mechanisms. The results of DNS
queries may also differ from queries that use the Mac OS X DNS routing
library."

 

If you have configured "foo" for 192.168.1.65 and it works, then that is the address it is using.

 

Do you have a problem with your local network that you are trying to fix?

Tutor

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5 Messages

6 y前

Thanks for the reply. Maybe I was not clear in my original message. If my computers are going to the router for resolution, which they are, and the router has assigned the address 192.168.1.65 to 'foo', which it has, then when I attempt to communicate with foo from another computer, the router should give me that .65 address. So I do indeed expect 'nslookup foo' to return 192.168.1.65, just as I'd expect 'ssh foo' to connect me to 192.168.1.65. It does not. The router returns a different IP. Neither rebooting the router not clearing the device list and rescanning the devices resolves the problem.

ApexRon

Professor

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2.2K Messages

6 y前

" If my computers are going to the router for resolution..." Name resolution in a TCP/IP world requires a Domain Name Server (DNS) for which the AT&T router/gateway is not. Names in a local network are only used in a Windows Internet Name Server (WINS) environment using NetBIOS.

 

When I perform a nslookup using the name for my pc the reply that comes back is that my DNS server, Google, cannot find. Which I would expect. This is the same reason why SSH cannot connect to a devices name in my local network, though I can connect using their IP address. 

Tutor

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5 Messages

6 y前

Allowing DHCP to configure my network services results in this, correct, /etc/resolv.conf file.

 

$ cat /etc/resolv.conf
# Generated by resolvconf
search attlocal.net
nameserver 192.168.1.254

 

The router absolutely does provide name resolution. I can even query it on port 53. I can query it as a server via dig and it will return an answer. But it will be the wrong answer.

 

$ dig @192.168.1.254 diskstation_leo

; <<>> DiG 9.11.0-P1 <<>> @192.168.1.254 diskstation_leo
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55816
;; flags: qr aa rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;diskstation_leo.        IN    A

;; ANSWER SECTION:
diskstation_leo.    0    IN    A    192.168.1.65

 

Perhaps this is the result of stale entries that I can't seem to get rid of. What I would like to know is how to get rid of them.

Tutor

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5 Messages

6 y前

ApexRon

Professor

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2.2K Messages

6 y前

You are mixing terms. A public Domain Name Server uses registered names that equate to IP addresses. What the AT&T router/gateway is more appropriately termed a "local domain names cache" which may be stored in memory or non-volatile memory and is only used on its network and cannot be propagated upstream or downstream to other networks.

 

I am not sure what you are trying to achieve by using names but to rely on a device you have no engineering control over to provide that service may not be a good solution.

 

I would be interested to find out if the other forum solution helped. Keep me posted.

Tutor

 • 

5 Messages

6 y前

Factory resetting resolves the issue.

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