Menu
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?
664
IPv4 uses 32-bit IP address, and with 32 bits the maximum number of IP addresses is 232—or 4,294,967,296. This provides a little more than four billion IPv4 addresses (in theory).
When your router receives a non-static DHCP assigned IP address from your ISP there is a pre-defined time limit built into the assignment, this time limit is called a DHCP Lease. The typical lease time for ISP's in the United States is roughly 7 days.
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.
In IPv4, the IP address consists of 32 bits number. And we represent it by 4 octets (8-bits each).
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!)
166
For IPv4, you could get away with storing the 4 raw bytes of the IP address (each of the numbers between the periods in an IP address are 0-255, i.e., one byte). But then you would have to translate going in and out of the DB and that's messy.
IPv6 addresses are 128 bits (as opposed to 32 bits of IPv4 addresses). They are usually written as 8 groups of 4 hex digits separated by colons: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. 39 characters is appropriate to store IPv6 addresses in this format.
Edit: However, there is a caveat, see @Deepak's answer for details about IPv4-mapped IPv6 addresses. (The correct maximum IPv6 string length is 45 characters.)
22
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
