This is very important information that is always helpful whether you are a IT/Network/System Engineer:

Prefix size	Network mask	Available subnets	Usable hosts per subnet	Total usable hosts
/24	255.255.255.0	1	254	254
/25	255.255.255.128	2	126	252
/26	255.255.255.192	4	62	248
/27	255.255.255.224	8	30	240
/28	255.255.255.240	16	14	224
/29	255.255.255.248	32	6	192
/30	255.255.255.252	64	2	128
/31	255.255.255.254	128	2 *	256

Very necessary information!

Posted by user_2789677 at 2016-08-27 13:45 Very necessary information!

Yes, indeed. Most of the technical guys needs this information while they are doing their operation.

Normal case, but who already have CCNA will clealy about this. Better you should have more info about ip address