Archive for the ‘networking’ Category

ifconfig & Netmasks

Tuesday, July 29th, 2008

Whenever moving IPs around on servers I always find myself looking up the hex for a netmask.

Ever run into this

$ ifconfig

inet xxxxxxxxxxx netmask 0xfffffff0 broadcast xxxxxxxxxxxxxx

And need to know what the fffffff0 was for Here it is:

Dotted
Decimal		 Hex Number of
Addresses
255.0.0.0 FF000000 16777214 (16777216-2)
255.255.0.0 FFFF0000 65534 (65536-2)
255.255.255.0 FFFFFF00 254 (256-2)
255.255.255.128 FFFFFF80 126 (128-2)
255.255.255.192 FFFFFFC0 62 (64-2)
255.255.255.224 FFFFFFE0 30 (32-2)
255.255.255.240 FFFFFFF0 14 (16-2)
255.255.255.248 FFFFFFF8 6 (8-2)
255.255.255.252 * FFFFFFFC * 2 (4-2) *

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© 2008 Josh Rendek.