Max length for client ip address

sql database database-design
Tony Eichelberger picture Tony Eichelberger · Jul 2, 2009 · Viewed 157.1k times · Source

Possible Duplicate:
Maximum length of the textual representation of an IPv6 address?

What would you recommend as the maximum size for a database column storing client ip addresses? I have it set to 16 right now, but could I get an ip address that is longer than that with IPv6, etc?

Answer

Deepak picture Deepak · Sep 19, 2011

There's a caveat with the general 39 character IPv6 structure. For IPv4 mapped IPv6 addresses, the string can be longer (than 39 characters). An example to show this:

IPv6 (39 characters) : 

ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:ABCD

IPv4-mapped IPv6 (45 characters) : 

ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:192.168.158.190

Note: the last 32-bits (that correspond to IPv4 address) can need up to 15 characters (as IPv4 uses 4 groups of 1 byte and is formatted as 4 decimal numbers in the range 0-255 separated by dots (the . character), so the maximum is DDD.DDD.DDD.DDD).

The correct maximum IPv6 string length, therefore, is 45.

This was actually a quiz question in an IPv6 training I attended. (We all answered 39!)

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