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Find Hostname from IP Address

Let's say you have a large internal global network and you have an IP address that is slamming your SAP server that is coming from a different network segment with a different DNS server.

How do you know what host that is?

In a large network, there might be different domains and different DNS servers. You can query your local DNS server:

nslookup 1.2.3.4

But the local DNS won't find it because the host is not registering with that Name Server.

So to make this work, find the DNS server on that network segment. Sometimes using a traceroute helps here:

tracert 10.20.30.40

This will show the network hops. Hopefully this will narrow down the DNS server for that segment and query it, like this:

nslookup 10.20.30.40 11.22.33.44

It will return the FDQN and IP address.