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I have to create a field in a mysql table to store ip addresses. I need to know the maximum characters an ip address can possibly be. Whether ipv4, ipv6 or some other type that can render a valid ip address unusually long. So what should I set the character limit to?

I am asking for length in the sense that the word "foo" has 3 characters, not in terms of bytes or anything like that.

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2 Answers 2

up vote 8 down vote accepted

An IPv6 address, at its longest, would be 8 sets of 4 characters (32 total), each set separated by a colon. That makes 39 characters.

An IPv4 address is at most 4 sets of 3 numbers (12 characters), each set separated by a dot (.). That makes 15 characters.

All of this assumes the IP addresses should be stored in human-readable form. I prefer to store IP addresses in decimal form, as you never quite know how it will be used. Your mileage may vary.

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Thanks a lot, human readable form is fine for my use case as I am never going to use them generally. I am only storing the ips of people who signup on my site in case they ever upload anything seriously offending and I have to hand over their info to authorities. –  Lonand Jan 22 '12 at 0:17

If you include the slash notation, e.g.

255.255.255.255/32

then it can be up to 18 characters.

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