Chuong Vu
Professor M. Moghimi
NST 231 – 01 Networking II
VLSM Report
I. VLSM
As the IP networks grow larger, the network administrator must use the IP address space
more efficiently. One of the network techniques is use the VLSM (Variable-Length Subnet
Mask). In generally, VLSM is used to save the IP address space in the network. For example,
you want to build a network contain only 5 IP address. Even by using the IP Address Class C,
you will have 249 excess IP Address (254 - 5 = 249).
So, you can use VLSM to split to smaller networks. Instead of using IP address
192.233.241.0/24 from 192.233.241.1 to 192.233.241.254 (Subnet Mask 255.255.255.0). You
can use 192.233.241.0/29 from 192.233.241.1 to 192.233.241.6 (Subnet Mask 255.255.255.248).
VLSM allows an organization use different Subnet Mask in a large Network to maximize
address space.
For easy to understand the VLSM, I use the Cisco Packet Tracer to setup a VLSM
networks.
II. Create three networks
Network 1: Router 1, Switch 1, PC1, PC2
Network 2: Router 2, Switch 2, PC3, PC4
Network 3: Router 1 and Router 2 connected by Serial DCE cable.
III. Setup IPs
1) Set IP address for Network 1. Says Network 1 allowed only 8 hosts (SA=128).
Ethernet Cable
Router 1
PC1
PC2
IP Address
192.233.241.129
192.233.241.130
192.233.241.131
Subnet Mask
255.255.255.240
255.255.255.240
255.255.255.240
192.233.241.129
192.233.241.129
Gateway
2) Set IP address for Network 2. Says Network 2 allowed only 25 hosts (SA=64).
Ethernet Cable
Router 2
PC3
PC4
IP Address
192.233.241.65
192.233.241.66
192.233.241.67
Subnet Mask
255.255.255.224
255.255.255.224
255.255.255.224
192.233.241.65
192.233.241.65
Gateway
3) Network 3 only needs 2 hosts that contain Router1 and Router2 (SA = 8). IP Address will be:
Serial DCE Cable
Router 1
Router 2
IP Address
192.233.241.9
192.233.241.10
Subnet Mask
255.255.255.252
255.255.255.252
IV. RIP v2
To make each host in both Networks can ping to each other. We use RIPv2.
In the CLI menu of Router, use the follow command to enable the connection between
Router 1 and Router 2.
By using this configuration, all the PCs in Network 1 and 2 can ping to each other now.
V. Conclusion
VLSM is very useful for the network administrator want to save the IP Address and split
the IP Address in the same Class to smaller networks. By using this, the network administrator
can easy control the networks group like building to building or room to room.