What is network namespace?

In Linux, a network namespace is a virtual area that separates network configurations. It assists in keeping various processes or applications apart, each with its network environment, to stop them from interfering with one another.

We can connect network namespaces using two methods:

1. Create two Namespaces and connect them using veth (VM)
2. Create two Namespaces and connect them using Linux bridge (VM/web)

Let’s start…

Create two Namespaces and connect them using veth (vm)

Step 1: Check the list of network namespaces and add two new name spaces

sudo ip netns list

sudo ip netns add ns1 
sudo ip netns add ns1

So we created two name spaces ns1 and ns2.

Step 2: Now we can create a virtual ethernet to connect them

sudo ip link add veth1 type veth peer veth2

Here, veth1: This is one end of the virtual Ethernet pair. veth2: This is the other end of the virtual Ethernet pair.

Step 3: Connect the two pair of virtual Ethernet with two namespaces respectively

sudo ip link set veth1 netns ns1
sudo ip link set veth2 netns ns2

Now, we can check name spcaes are conneted with virtual Ethernet pair using this commands,

sudo ip netns exec ns1 ip link
sudo ip netns exec ns2 ip link

Step 4: Assign IP Addresses to Each Namespace Using Their Respective Devices — Utilize veth1 for ns1 and veth2 for ns2.

sudo ip netns exec ns1 ip addr add 192.168.1.1/24 dev veth1
sudo ip netns exec ns2 ip addr add 192.168.1.2/24 dev veth2

Step 5: Activate the IP links for each namespace.

sudo ip netns exec ns1 ip link set veth1 up
sudo ip netns exec ns2 ip link set veth2 up

We can accetive the loopback as well

sudo ip netns exec ns1 ip link set lo up
sudo ip netns exec ns2 ip link set lo up

Step 6: Now its time to test the connection

Execute the following command to ping ns2 from ns1:

sudo ip netns exec ns1 ping 192.168.1.2

Execute the following command to ping ns1 from ns2:

sudo ip netns exec ns2 ping 192.168.1.1

Furthermore, examining the ARP table for ns1 reveals its ability to identify its neighboring device.

ubuntu@ubuntu:~$ sudo ip netns exec ns1 arp
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.1.2                      (incomplete)                              veth1

Hence, The connection between the two namespaces has been established seamlessly through the use of veth.

Now, 2nd Method

Create two Namespaces and connect them using Linux bridge (VM/web)

Step 1: Check the list of network namespaces and add two new name spaces

sudo ip netns list

sudo ip netns add ns1 
sudo ip netns add ns1

So we created two name spaces ns1 and ns2.

Step 2: Establish a Linux bridge with the name v-net

 sudo ip link add v-net type bridge

now we can up the state of the v-net

 sudo ip link set v-net up

Step 3: Assign an IP address to the bridge interface v-net

sudo ip addr add 10.0.0.1/24 dev v-net

Step 4: Now, create two virtual Ethernet interfaces using the veth type.

sudo ip link add veth1 type veth peer name veth-1-br
sudo ip link add veth2 type veth peer name veth-2-br

Step 5: Connect the veth1 end of the first virtual Ethernet to ns1, and link the veth2 end of the second virtual Ethernet to ns2.

sudo ip link set veth1 netns ns1
sudo ip link set veth2 netns ns2

Step 6: Now, link the other end of the first virtual Ethernet (veth-1-br) with the bridge (v-net), and similarly, connect the other end of the second virtual Ethernet (veth-2-br) to the same bridge (v-net).

sudo ip link set veth-1-br master v-net
sudo ip link set veth-2-br master v-net

We’re all set! It’s now time to assign IP addresses to the network namespaces.

Step 7: Assign IP Addresses to Each Namespace Using Their Respective Devices — Utilize veth1 for ns1 and veth2 for ns2.

sudo ip netns exec ns1 ip addr add 192.168.1.1/24 dev veth1
sudo ip netns exec ns2 ip addr add 192.168.1.2/24 dev veth2

Step 8: Activate the IP links for each namespace.

sudo ip netns exec ns1 ip link set veth1 up
sudo ip netns exec ns2 ip link set veth2 up

sudo ip link set dev veth-1-br up
sudo ip link set dev veth-2-br up

We can accetive the loopback as well

sudo ip netns exec ns1 ip link set lo up
sudo ip netns exec ns2 ip link set lo up

Step 9: Now its time to test the connection again

Execute the following command to ping ns2 from ns1:

sudo ip netns exec ns1 ping 192.168.1.2

Execute the following command to ping ns1 from ns2:

sudo ip netns exec ns2 ping 192.168.1.1

Furthermore, examining the ARP table for ns1 reveals its ability to identify its neighboring device.

ubuntu@ubuntu:~$ sudo ip netns exec ns1 arp
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.1.2                      (incomplete)                              veth1

Also we can set Firewall rules:

sudo iptables --append FORWARD --in-interface v-net --jump ACCEPT
sudo iptables --append FORWARD --out-interface v-net --jump ACCEPT