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So, for example, the domain google.com points to the domain sfo07s13-in-f14.1e100.net (depending on where you're browsing) which then points to an IP address of

So, for example, the domain google.com points to the domain sfo07s13-in-f14.1e100.net (depending on where you're browsing) which then points to an IP address of the server that's serving you the content. google.com -> subdomain.1e100.net -> server IP address Then when you run a reverse DNS on the IP address, you get sfo07s13-in-f14.1e100.net. rDNS: server IP address -> subdomain.1e100.net So, like you said, if something is wrong with the server, you can run a reverse DNS on the IP address to get the subdomain sfo07s13-in-f14.1e100.net. Is this the correct understanding? But don't you already have the IP address of the misbehaving machine?

tlb 8y ago
Yes. The name sfo07s13-in-f14 is mnemonic to Google engineers -- it's probably in San Francisco data center 7. Also, that server probably has both an IPv4 and IPv6 address. Also, sometimes IP addresses change but you want servers to keep their identity. So names are convenient.
peterwwillis 8y ago
Lots of people look at IP addresses. Most of the people who find the "1e100.net" records in their network logs would have no easy way of knowing that 1.2.3.4 (or whatever) was a Google IP. The reverse lookup allows you to easily find out what domain it belongs to (1e100.net, which a Google search shows is a Google address). You can also embed other information in the reverse name, such as the region, datacenter, floor, switch, rack, or unit number of the machine. It can be incredibly easy to locate the machine by just looking at its reverse name. "Oh, 1.2.3.4 is in us-east-1, on floor 3, in rack 27, unit 5. Let me go check the network cable."