DNS Query

hi Experts,

In our environment, We have 7 Physical servers running about 25 virtual machines.
Over the weekend we had a power outage. All servers except one physical server running primary DNS server came up.  We had to fix the server and start Primary DNS server to bring the cluster up.All our servers have static IP Address . We believe it is an issue with DNS.  We checked logs in all DC's for replication errors.
Our primary DNS IPAddress is 172.16.1.3
Secondary DNS IPAddress is 172.16.1.2

To test it I assigned static DNS to my computer. Preferred as 172.16.12 and additional as 172.16.1.3.
Shutdown 172.16.1.2 and ran nslookup on my computer. It is not falling back to 172.16.1.3.
I am able to access internet normally but how come nslookup is failing?
I am getting results as below
>nslookup
DNS request timed out.
    timeout was 2 seconds.
Default Server:  UnKnown
Address:  172.16.1.2

www.gmail.com
Server:  UnKnown
Address:  172.16.1.2

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
*** Request to UnKnown timed-out
LVL 1
ukitsmeAsked:
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Zacharia KurianAdministrator- Data Center & NetworkCommented:
Could you make sure the following?
1. Every DNS servers point to its own IP as the primary DNS and the DNS of other additional DCs are added as the secondary DNS?
2. All the unused NICs are disabled.
3. Valid DNS IPs from ISP are configured in DNS forwarders.
4. Public DNS IP's are not used at any NIC Card except Forwarders.
5. Domain Controllers are not multi-homed.

Also run the command in your DCs,  dcdiag /test:DNS and look into the results. You could also check the last default route in your network i.e.. any unresolved DNS queries should pass through your Fire wall /Router. Execute  route print from the command prompt of the PC and post results.

Zac.
Zephyr ICTCloud ArchitectCommented:
Nslookup does not automatically choose another DNS server than the one which is configured as your primary...
You'll have to manually set the new DNS server to query (server <ip-of-dns-server>) ... In other words, nslookup is an interactive tool.
DrAtomicCommented:
nslookup is failing because the tool nslookup only uses the defined primary dns server if you do not define a specific dns server to use.

If you want to test if a different nameserver responds correctly you'll have to define that;
in interactive mode you enter server [enter] ip address [enter]
in direct mode you use: nslookup www.gmail.com 172.16.1.3

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DNS

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