How to match IPv4 addresses

Question

I am trying to have my regex match the following:

169.254.0.0-169.254.254.255

Could anyone please help how can I achieve this.

so far I have this:

169\.254\.([1-9]{1,2}|[1-9]{1,2}[1-4])

but it would also pick up 169.254.255.1 which should not be one of the matches.

Please help!

thanks

Answer 1

I've written an article that provides regular expressions for all the components of a generic URI (as defined in RFC3986: Uniform Resource Identifier (URI): Generic Syntax)

See: Regular Expression URI Validation

One of the components of a generic URI is an IPv4 address. Here is the free-spacing mode Python version from that article:

re_python_rfc3986_IPv4address = re.compile(r""" ^
    # RFC-3986 URI component:  IPv4address
    (?: (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?) \.){3}  # (dec-octet "."){3}
        (?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)         # dec-octet "."
    $ """, re.VERBOSE)

And the un-commented JavaScript version:

var re_js_rfc3986_IPv4address = /^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/;

Answer 2

This is the regex I use for general IP validation:

(([0-9](?!\d)|[1-9][0-9](?!\d)|1[0-9]{2}(?!\d)|2[0-4][0-9](?!\d)|25[0-5](?!\d))[.]?){4}

Breakdown:

1.`[0-9](?!\d)`       -> Any Number 0 through 9 (The `(?!\d)` makes sure it only grabs stand alone digits)
2.`|[1-9][0-9](?!\d)` -> Or any number 10-99 (The `(?!\d)` makes sure it only grabs double digit entries)
3.`|1[0-9]{2}`        -> Or any number 100-199
4.`|2[0-4][0-9]`      -> Or any number 200-249
5.`|25[0-5]`          -> Or any number 250-255
6.`[.]?`              -> With or without a `.`
7.`{4}`               -> Lines 1-6 exactly 4 times

This hasn't failed my yet for IP address validation.

For your specific case, this should do it:

(169\.254\.)((([0-9](?!\d)|[1-9][0-9](?!\d)|1[0-9]{2}|2[0-4][0-9]|25[0-4])[.])(([0-9](?!\d)|[1-9][0-9](?!\d)|1[0-9]{2}|2[0-4][0-9]|25[0-5])))

This is very long because I couldn't figure out how to get 169.254.(0-254).255 to check without getting 169.254.255.1 to fail

Edit: Fixed due to comments

Answer 3

the regex ([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-4]) matches 0-254.

see this page for more discussion