DNS Response Issue

Linux and Unix-Like Linux
1

Hi,

I have a Windows based Domain (abc.com)servers like:

172.30.1.246
172.30.1.247
172.30.3.246
172.30.3.247

On all my Linux servers (/etc/resolv.conf) have a following DNS servers entries:

nameserver 172.30.3.246
nameserver 172.30.3.247

But when i ping my Domain (abc.com), it always get a response from 172.30.1.246, 172.30.1.247

2

We understand the environment now, and the problem is what?

3

Problem is that, i mentioned a following DNS servers address in /etc/resolv.conf:

172.30.3.246
172.30.3.247

But always get a ping response from the following DNS servers which is not mentioned in /etc/resolv.conf:

172.30.1.246
172.30.1.247

4

So is the problem that DNS doesn't work?

If so, why are you talking about ping response from other ip addresses? If those ip addresses exist on your network, then ping responses are no surprise. Why are you connecting the ping responses from 172.30.1.246/7 with DNS servers on 172.30.3.246/7

Are 172.30.1.246/7 the Windows domain controllers?

Do the DNS servers 172.30.3.246/7 work for DNS resolution for the Windows clients?

I am sorry but I still don't understand the issues properly. What happens if you ping the DNS server address(es) from Linux boxes?

5

You can force a particular DNS to be queried like this:-

nslookup unix.com 172.30.3.246

Does that help?

It may be that your server tries only a few by default, but if some go offline then it will go to the others too. What happens if you knowingly set the first two addresses to servers that don't offer DNS? Does a ping or nslookup still work?

Robin

6

In the Unix/Linux world nobody pings the domain. There can be zero servers configured.
DNS needs the following only

nslookup -q=ns my.domain

The result is important for all DNS servers. While caching-only servers do not need to show up there. The clients rely on the resolv.conf only.
I guess your Linux systems have caching-only servers configured.