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) *