Building the experiment topology

This section shows the steps required to build the experiment topology shown in the lab topology section. This will be done by creating two Linux namespaces and configuring the interfaces so that a connection between them is established.

Namespaces are a feature that partitions Linux resources. Linux namespaces provide independent instances of networks that enable network isolation and independent operations. Each network namespace has its own networking devices, IP addresses, routing tables, and firewall rules [8].

Creating namespaces

Step 1. Issue the command sudo su on the terminal to enter root mode. When prompted for a password, type password and hit enter. Note that the password will not be visible as you type it:

sudo su

Figure 29: Entering root mode.

Step 2. Type the following command to create a namespace, h1:

ip netns add h1

Figure 30: Creating a namespace h1.

Step 3. Type the following command to create another namespace, h2:

ip netns add h2

Figure 31: Creating a namespace h2.

Attaching virtual device interfaces to namespace

In this section, you will attach dtap0 to namespace h1 and dtap1 to namespace h2.

Step 1. Type the following command to link the interface dtap0 to the namespace h1:

ip link set dtap0 netns h1

Figure 32: Linking namespace h1 to dtap0.

Step 2. Type the following command to link the interface dtap1 to the namespace h2:

ip link set dtap1 netns h2

Figure 33: Linking namespace h1 to dtap1.

Step 3. Type the following command to activate the interface dtap0:

ip netns exec h1 ip link set dev dtap0 up

Figure 34: Turning up the interface, dtap0.

The command ip netns exec takes two arguments; the namespace and the command to run in the specified namespace. In the figure above, the command ip link set dtap0 up will be executed in namespace h1.

Step 4. Type the following command to activate the interface dtap1:

ip netns exec h2 ip link set dev dtap1 up

Figure 35: Turning up the interface, dtap1.

In the figure above, the command ip link set dtap1 up will be executed in namespace h2.

Assigning IP addresses to the interfaces

Step 1. Configure the dtap0 interface in the namespace h1 with an IP address and subnet mask by typing the following command.:

ip netns exec h1 ifconfig dtap0 192.168.10.1/24

Figure 36: Configuring the interface, dtap0.

Step 2. Configure the dtap1 interface in the namespace h2 with an IP address and subnet mask by typing the following command.:

ip netns exec h2 ifconfig dtap1 192.168.10.2/24

Figure 37: Configuring the interface, dtap1.

Establishing connection between namespaces

Step 1. Add a static ARP entry to the ARP cache in h1 to associate the IP address in the namespace h2 192.168.10.2 with its MAC address 00:00:00:00:00:02.:

ip netns exec h1 arp -s 192.168.10.2 00:00:00:00:00:02

Figure 38: Adding a static ARP entry in host h1.

Step 2. Add a static ARP entry to the ARP cache in h2 to associate the IP address in the namespace h1 192.168.10.1 with its MAC address 00:00:00:00:00:01.:

ip netns exec h2 arp -s 192.168.10.1 00:00:00:00:00:01

Figure 39: Adding a static ARP entry in host h2.