[cpeterso]

I don't see any requests to 1e100.net when loading Google sites like google.com or youtube.com. I see domains like gstatic.com and apis.google.com, but but not 1e100.net.

[TimTheTinker]

You can think of all user-facing domains in a system as an interface or API, which abstracts away implementation details about which specific servers are behind them.

This allows flexibility in infrastructure — you can swap machines in and out (e.g. by updating public DNS records, updating the machines’ IP addresses, or adding them to (or removing them from) a load balanced pool behind a reverse proxy). But you still need a way to reference individual machines regardless of whether they’re serving or not.

That’s where domains like 1e100.net come in — a system of concrete (non-abstract) references to specific machines in your infrastructure.

[yebyen]

Try a reverse lookup

  yebyen:~$ host google.com
  google.com has address 172.217.10.46
  google.com has IPv6 address 2607:f8b0:4006:803::200e
  ...

  yebyen:~$ host 172.217.10.46
  46.10.217.172.in-addr.arpa domain name pointer lga34s13-in-f14.1e100.net.

[forgottenpass]

You wouldn't. Multiple domain names can point to the same IP address. Any one IP address can only have one reverse (PTR) record.

[Buge]

    $ ping google.com
    PING google.com (172.217.7.206) 56(84) bytes of data.
    64 bytes from iad30s10-in-f14.1e100.net (172.217.7.206): icmp_seq=1 ttl=48 time=0.676 ms