CCNA part 3 subnetting

1. SUBNETTING

2. Advantages of Subnetting:-
• Reduce network Traffic.
• Optimized network performance.
• Simplified management.
• Facilitated spanning of large geographical
distance.
• Bandwidth utilization will increase.

3. Formula For Subnetting:-
• 2^h – 2 >= No. of host per network.
Where h:- no host Bits
• 2^n – 2 >= No. of sub networks.
Where n:- no network Bits

4. Examples of Class C:-
• Required hosts are:-40
• 2^h – 2 >= 40 hosts.
• 2^6 – 2 >= 40 hosts hence h=6 & n= 2
• No of Subnetworks 2^2 – 2=2subnetworks.
• Subnetworks are:-
• 192.168.1.0 – 192.168.1.63
192.168.1.64 – 192.168.1.127
192.168.1.128 – 192.168.1.191
192.168.1.192 – 192.168.1.255
Subnetmask= 255.255.255.192

5. Examples of Class C:-
• Required hosts=2
• Bits h=2 and n=6.
• No of subnetworks = 64-2=62
• Subnetmask= 255.255.255.252
• Range of network=4

6. Examples of Class C:-
• Ex. 192.168.1.0/28
Network Bits n=4 and host Bits =4.
• No. of Subnets=14
• No 0f host/Net =14
• Subnetmask =255.255.255.240
• Range of network is =16

7. Examples of Class C:-
• Ex. 192.168.1.0/29
Network Bits n=5 and host Bits =3.
• No. of Subnets=30
• No 0f host/Net =6
• Subnetmask =255.255.255.248
• Range of network is =8

8. Examples of Class B:-
• Ex. 172.16.0.0/18
Network Bits n=2 and host Bits =14.
• No. of Subnets=2
• No 0f host/Net =16382
• Subnetmask =255.255.192.0.0
• Range of network is:-
172.16.0.0 ------- 172.16.63.255
172.16.64.0 ------- 172.16.127.255
172.16.128.0 ------- 172.16.191.255
172.16.192.0 ------- 172.16.255.255

9. VLSM
• Variable length subnet mask.
• Subnetting of Subnets.
• Formula:-
2^h – 2 >= No. of host per network.
Where h:- no host Bits
2^n >= No. of sub networks.
Where n:- no network Bits

10. Example of VLSM:-
Subnetting:- (class C)
• E.g.:-192.168.1.0
• Required hosts are:-60
• I.e. h=6 & n= 2
• Subnetworks are:-
192.168.1.0 – 192.168.1.63
192.168.1.64 – 192.168.1.127
192.168.1.128 – 192.168.1.191
192.168.1.192 – 192.168.1.255
Subnetmask= 255.255.255.192
VLSM:-
• E.g. 192.168.1.64 (255.255.255.192)
• Required host are:-14.
• Now n+h=6
• 2^h – 2 = no of host per subnet.
I.e. h=4and n= 2
• 2^ n = no subnet I.e. 4 subnetworks
• Subnetworks are:-
192.168.1.64 – 192.168.1.79
192.168.1.80 – 192.168.1.95
192.168.1.96 – 192.168.1.111
192.168.1.112 – 192.168.127.
• New subnetmask= 255.255.255.240

11. CIDR
• Classless inter-domain routing.
• It’s basically the method that ISPs use to allocate an
amount of address to a company (home – customer).
• CIDR Values:-
subnet mask CIDR value
255.0.0.0 /8
255.128.0.0 /9
255.192.0.0 /10
255.255.255.252 /30