Lab 6 - Subnetting
From SOFTICE
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Pedagogical Objectives
- Build upon the Binary and Hexadecimal and Classful IP Addressing labs to explain subnetting
- Design and implement subnetting schemes
Developed by:
Synopsis
[Briefing]
In the previous lab, we introduced the idea of IP subnetting in classful networks. In classful networks, the subnets in a given network all have the same subnet mask. That is, the number of bits allocated to the network and host portions of a 32-bit IP address are fixed. This scheme, while simple can lead to inefficiencies. For example, if an organization only needs to address three hosts in a network, allocating a class C block is horribly inefficient.
This lab will discuss classless subnetting - a technique in which the number of bits allocated to the network and hosts may be set to the most efficient balance.
[Solved]
Complete the following solved exercise, recording your findings, and the procedures used to obtain them in your log. By doing this, you may be able to obtain partial credit if you are unable to complete any of the exercises.
Note: Before disconnecting from SOFTICE, be sure to shut your virtual hosts down. This procedure is described in Exercise 1-3: Shutdown the Network. This must be done in order to conserve system resources on the SOFTICE cluster.
Solved 6-1: Subnet the Ring Network
The Ring Network has been assigned the 10.16.0.32/28 IP block. Edit the Ring Network's configuration file, reconfiguring each host appropriately. Work with the following assumptions:
- All WANs (Wide Area Networks) have two hosts
1. Start by determining what subnet mask to assign each network. As stated above, each WAN (Wide Area Network) should be able to accommodate two hosts. Using the usable hosts formula that we learned in the previous lab, let's find an appropriate subnet mask:
- 1 bit isn't enough:
21-2=0
- 2 bits are:
22-2=2
- Let's make sure that this will allow for enough subnets to be created. When we started off with a /28 IP block, there were 4-bits being allocated to addressing hosts. Since we now plan to use /30 IP blocks to address each WAN, we've gained 2-bits for addressing network:
30-28=2
- Using the usable networks formula that we learned in the previous lab, let's find out how many networks can be created with these 2-bits:
22=4
- Now that we know that two bits should be allocated to addressing hosts, let's calculate the subnet mask. Set each bit that's used to address the network to one, and each bit that's used to address a host to 0:
11111111.11111111.11111111.11111100
- After converting the above to decimal, we get:
255.255.255.252
2. Now let's edit the Ring Network's configuration file, reconfiguring each host appropriately.
- Copy the ring.mln configuration file to a writable directory. The original ring.mln file is in the write protected mln_files directory.
cd mln cp mln_files/ring.mln files/solved-6-1.mln
- Edit your copy of the Ring Network's configuration file.
nano files/solved-6-1.mln
- The following is one possible solution to this exercise. The modified lines are shown in red.
global {
project ring
$console = screen
}
switch lakelandTampa {}
switch lakelandOrlando {}
switch tampaOrlando {}
superclass hosts {
term $console
kernel = /home/sys/net/bin/linux-2.6.18.1/linux
template = DebianNet-3.1-v1.ext2
size 300M
}
host lakeland {
superclass hosts
cow_filesystem lakeland.cow
network eth0 {
switch lakelandTampa
address 10.16.0.33
netmask 255.255.255.252
}
network eth1 {
switch lakelandOrlando
address 10.16.0.37
netmask 255.255.255.252
}
}
host tampa {
superclass hosts
cow_filesystem tampa.cow
network eth0 {
switch lakelandTampa
address 10.16.0.34
netmask 255.255.255.252
}
network eth1 {
switch tampaOrlando
address 10.16.0.41
netmask 255.255.255.252
}
}
host orlando {
superclass hosts
cow_filesystem orlando.cow
network eth0 {
switch tampaOrlando
address 10.16.0.42
netmask 255.255.255.252
}
network eth1 {
switch lakelandOrlando
address 10.16.0.38
netmask 255.255.255.252
}
}
[Exercises]
Complete the following exercises, recording your findings, and the procedures used to obtain them in your log.
Note: Before disconnecting from SOFTICE, be sure to shut your virtual hosts down. This procedure is described in Exercise 1-3: Shutdown the Network. This must be done in order to conserve system resources on the SOFTICE cluster.
Exercise 6-1: Subnet the Tcpdump Network
1. The Tcpdump Network has been assigned the 192.168.0.64/29 subnet. Create a new copy of the Tcpdump Network's configuration file, then reconfigure each host appropriately.
2. Verify connectivity between all hosts located on the same subnet.
Exercise 6-2: Subnet the Two Locations Network
1. The Two Locations network has been assigned the 192.168.54.128/25 IP block. Create a new copy of the Two Locations Network's configuration file, then reconfigure each host appropriately. Work with the following assumptions:
- All WANs (Wide Area Networks) have two hosts
- All LANs require the ability to support at least 20 hosts
2. Verify connectivity between all hosts located on the same subnet.
Exercise 6-3: Subnet the Three Locations Network
1. The Three Locations network has been assigned the 10.100.5.0/24 IP block. Create a new copy of the Three Locations Network's configuration file, then reconfigure each host appropriately. Work with the following assumptions:
- All WANs (Wide Area Networks) have two hosts
- All LANs require the ability to support at least 60 hosts
2. Verify connectivity between all hosts located on the same subnet.
