I'm new to networking. I know that some IPs don't have a sub net mask like and the range that starts with 127. I wanted to know if there is any other IPs that don't have sub net mask.

1 Answer 1


IP addresses don't have subnet masks. Networks do. For the loopback address, the entire /8 is reserved, so it's or

  • So the IPs that have 127 as their first octet, have netmask too? For example for, the netmask is
    – Pablo
    Jun 12, 2020 at 19:45
  • @Pablo The reserved loopback is, so you can use any address from to
    – Zac67
    Jun 12, 2020 at 19:49
  • 1
    The loopback address is a special reserved case (See RFC 1122).
    – Ron Trunk
    Jun 12, 2020 at 19:49

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