Subnetting

Steps:

1. Convert Address and Mask to Decimal
2. Calculate the Network Address: If the Mask is 255, Bring Down the Adress. If the Mask is 0 use 0 (Other Numbers Refer to Chart 2)
3. Calculate the Broadcast Address: If the Mask is 255, Bring Down the Adress. If the Mask is 0 use 255
4. First IP:Network Address +1
5. Last IP:Broadcast Address -1

Chart 1:

Column 1	Column 2	Column 3	Column 4	Mask	Network	Addresses
/1	/9	/17	/25	128	2	128
/2	/10	/18	/26	192	4	64
/3	/11	/19	/27	224	8	32
/4	/12	/20	/28	240	16	16
/5	/13	/21	/29	248	32	8
/6	/14	/22	/30	252	64	4
/7	/15	/23	/31	254	128	2
/8	/16	/24	/32	255	256	1

Chart 2:

Examples:

Address: 165.245.10.77/24

Address	165	245	10	77
Mask	255	255	255	0
	↓	↓	↓	↓
Network Address	165	245	10	0
Broadcast Address	165	245	10	255
First Ip	165	245	10	1
Last Ip	165	245	10	254

1. Column 3: /24 Mask:255
2. Bring Down Address and use 0
3. Bring Down Address and convert 0
4. Network Address +1
5. Broadcast Address -1

Address: 165.245.10.77/26

Address	165	245	10	77
Mask	255	255	255	192
	↓	↓	↓	↓
Network Address	165	245	10	64
Broadcast Address	165	245	10	127
First Ip	165	245	10	65
Last Ip	165	245	10	126

1. Column 4: /26 Mask:192
2. Bring Down Address, Mask 192 has Address 64: 77 falls into row 64
3. Bring Down Address Last Number in Row is 127
4. Network Address +1
5. Broadcast Address -1

Cheat Sheet:
*Subtract 2 from Host

Why Not Use a Tool: https://www.ipaddressguide.com/