Would 256.256.256.256 be Considered a Valid Hostname?

Answer: No, 256.256.256.256 will not be considered a valid hostname.

A hostname is defined as a unique label that is being assigned to each device that is connected over a computer network. Hostname helps to easily distinguish it from other available network devices as it is in human-readable form.

Why 256.256.256.256 will not be considered a valid hostname?

Under TLD 256.256.256.256 is considered as a invalid IP address and not as a valid host name. Because ICAN by default bans all the numeric TLDs for a valid host name. In terms of IP address, each segment of the IP address must be between 0 and 255 only. Therefore for IPv4 address, using 256 will not be considered as a valid octet value for the IPv4 address.

A hostname consists of a to z letters, numbers and hyphens that follows a rules for length and placements too.

Below are the rules, maintained by The Internet Engineering Task Force (IETF) for the hostname:

1. The length of hostname must be between 1 and 63 ASCII characters only.

2. Hostname is case-insensitive

3. Characters allowed in hostname are: a to z, 0-9, -(hyphen)

4. A FQDN is of maximum 253 ASCII characters in length.

Conclusion

As 256.256.256.256 does not meet the rules that are specified for a valid hostname, is is considered as invalid as well as invalid IP address too.