Network namespaces and VETH

Steps to create a pair of namespace and connect them.

1. Create the namespaces using

# sudo ip netns add <ns_name>
sudo ip netns add ns1
sudo ip netns add ns2

1. Connect these namespaces using a virtual ethernet (created in pairs) using:

#sudo ip link add <if_name> netns <ns_name> type veth peer name <peer_name> netns <peer_ns>
$ sudo ip link add veth0 netns ns1 type veth peer name veth1 netns ns2

This will create veth0 in ns1 and veth1 in ns2.

3. Assign IP addresses to these veth pairs using :

# sudo ip -n <ns_name> addr add <ip/mask> dev <if_name>
sudo ip -n ns1 addr add 10.1.1.1/24 dev veth0
sudo ip -n ns2 addr add 10.1.1.2/24 dev veth1

4. UP the interfaces using :

# sudo ip -n <ns_name> link set <if_name> up
sudo ip -n ns1 set veth0 up
sudo ip -n ns2 set veth1 up

5. Exec into the namespaces in different terminals and ping each other :

sudo ip netns exec ns1 ping 10.1.1.2    # in one terminal
sudo ip netns exec ns2 ping 10.1.1.1    # in another terminal

You can also exec bash in any namespace and execute commands interactively in that namespace :

sudo ip netns exec ns1 /bin/bash
# you will get a terminal now