IP_SUBNETTING

 

• Classful Network Concepts

    

Numbers and Sizes of Class A, B, and C Networks

Sizes (Bits) of the Network and Host Parts of Unsubnetted Classful Networks

Sizes (Bits) of the Network and Host Parts of Unsubnetted Classful Networks

Default Masks for Classes A, B, and C

Example of Deriving the Network ID and Other Values from 10.17.18.21

Example Deriving the Network ID and Other Values from 172.16.8.9

Practice Deriving Key Facts Based on an IP Address

Address Structure: Class B Network, /18 Mask

Network 172.16.0.0, Divided into Four Equal Subnets

Resident Subnet for 172.16.150.41, 255.255.192.0

Summary of Subnet ID Key Facts

 

Definition	Number that represents the subnet
Numeric Value	First (smallest) number in the subnet
Literal Synonyms	Subnet number, subnet address, prefix, resident subnet
Common-Use Synonyms	Network, network ID, network number, network address
Typically Seen In…	Routing tables, documentation

Binary Concept: Convert the IP Address to the Subnet ID

Converting the Subnet ID from Binary to DDN

Finding a Subnet Broadcast Address: Binary

Subnet Analysis for Address 8.1.4.5, Mask 255.255.0.0

Prefix Length:

/16 11111111 11111111 00000000 00000000

Address :

8.1.4.5 00001000 00000001 00000100 00000101

Subnet ID:

8.1.0.0 00001000 00000001 00000000 00000000

Broadcast Address:

8.1.255.255 00001000 00000001 11111111 11111111

Binary Shortcut Example

Practice Problems: Find Subnet ID and Broadcast, Easy Masks

 

	IP Address	Mask	Subnet ID	Broadcast Address
1	10.77.55.3	255.255.255.0
2	172.30.99.4	255.255.255.0
3	192.168.6.54	255.255.255.0
4	10.77.3.14	255.255.0.0
5	172.22.55.77	255.255.0.0
6	1.99.53.76	255.0.0.0

Numeric Patterns in the Interesting Octet

Find the Subnet ID: 130.4.102.1, 255.255.240.0

Resident Subnet for 192.168.5.77, 255.255.255.224

Practice Problems: Find Subnet ID, Difficult Masks

 

	IP Address	Mask	Subnet ID
1	10.77.55.3	255.248.0.0
2	172.30.99.4	255.255.192.0
3	192.168.6.54	255.255.255.252
4	10.77.3.14	255.255.128.0
5	172.22.55.77	255.255.254.0
6	1.99.53.76	255.255.255.248

Find the Subnet Broadcast: 130.4.96.0, 255.255.240.0

Find the Subnet Broadcast: 192.168.5.64, 255.255.255.224

 DOWNLOAD IP VLSM CIDR

Prefix, interesting octet 2	/9	/10	/11	/12	/13	/14	/15	/16
Prefix, interesting octet 3	/17	/18	/19	/20	/21	/22	/23	/24
Prefix, interesting octet 4	/25	/26	/27	/28	/29	/30
Magic number	128	64	32	16	8	4	2	1
DDN mask in the interesting octet	128	192	224	240	248	252	254	255

Prefix Length

/16

11111111 11111111 00000000 00000000

Prefix Length

/16

11111111 11111111 00000000 00000000

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111

 

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111

 

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111

  

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111

 

Prefix Length	/16	11111111 11111111 00000000 00000000
Address	8.1.4.5	00001000 00000001 00000100 00000101
Subnet ID	8.1.0.0	00001000 00000001 00000000 00000000
Broadcast Address	8.1.255.255	00001000 00000001 11111111 11111111