Score:0

DNS, why is it sometimes doing a PTR lookup before A lookup?

cn flag

When I perform NSLOOKUP -q=a chinaa.cn I get the following result in WireShark:

enter image description here

Why did it FIRST look up the PTR of my ISP DNS before sending an A-request?
And why did the DNS server respond first with with No such name with .home-appended to it?

cn flag
Probably so it can log which DNS server it used to do the lookup.
cn flag
@hardillb nope, because it only does this rarely
cn flag
Edit the question to show what's in your `/etc/resolve.conf`
cn flag
@hardillb , what's the windows-equivalent?
Score:4
uz flag

NSLOOKUP first displays the IP address of the DNS server it sends the request to, along with its DNS name. If the DNS name is not already in the DNS cache, then it sends a PTR request to get the name.

enter image description here

cn flag
And the reason it only does it intermittently is because it will be caching the response for the TTL. The answer to the second question will be because your DHCP server will be returning `.home` as a search path so it will checked first
mangohost

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.