NSLOOKUP not working if primary DNS server down

Question

Hi,

I have four domain controller in my environment. Two domain controller in DC site and another two in DR site. Replication among the domain controllers is okay. All the functionalities are also working well. This four domain controllers IP is placed in DNS of all workstations and servers. But my problem is when my primary domain controller is getting down, nslookup isn't working. But I checked that browsing is okay and I analyzed it with Wireshark and I found that when my primary domain controller is getting down, dns query was resolved by secondary domain controller. So, in here, no issue I found. Internet connectivity is okay and also query forwarding okay. But when I run nslookup google.com in cmd then it shows DNS timed out 2 seconds and it couldn't resolved the name but when I analyze it wireshark, I see that my seconday DNS resolved it. Even, If I put the secondary DNS as Primary DNS then It is also working. So, my question is how to fix this nslookup issue. Please give me a suggestion. Thanks in advance.

Answer 1

Hi @Md. Rubiat Haque •,

It's normal behavior , because by default nslookup can send DNS request only primary DNS resolver configured on the network card. If this DNS server is down , nslookup will not contact automatically the second IP in the list of DNS resolver. In this case You have to specify the IP of DNS server manually :

nslookup
server IPofSecondDNS

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