veth-example

Environment

• lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.5 LTS
Release:    18.04
Codename:   bionic

Example

• ip netns add test
• ip netns

test

• ip link add veth0 type veth peer name veth1 netns test: create a pair and then assign veth1 into namespace test
• ip addr show veth0: show it in the global namespace

130: veth0@if2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 8e:4c:e4:f8:df:aa brd ff:ff:ff:ff:ff:ff link-netnsid 15

• ip netns exec test ip addr: run ip addr under the test network namespace.

1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: veth1@if130: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether ca:83:85:f5:36:fe brd ff:ff:ff:ff:ff:ff link-netnsid 0

• ip addr add 10.1.1.1/24 dev veth0 && ip addr show veth0

130: veth0@if2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 8e:4c:e4:f8:df:aa brd ff:ff:ff:ff:ff:ff link-netnsid 15
    inet 10.1.1.1/24 scope global veth0
       valid_lft forever preferred_lft forever

• ip netns exec test ip addr add 10.1.1.2/24 dev veth1 && ip netns exec test ip addr show veth1

2: veth1@if130: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether ca:83:85:f5:36:fe brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 10.1.1.2/24 scope global veth1
       valid_lft forever preferred_lft forever

• ip link set veth0 up
• ip netns exec test ip link set veth1 up
• ping -I 10.1.1.1 10.1.1.2

PING 10.1.1.2 (10.1.1.2) from 10.1.1.1 : 56(84) bytes of data.
64 bytes from 10.1.1.2: icmp_seq=1 ttl=64 time=0.060 ms
64 bytes from 10.1.1.2: icmp_seq=2 ttl=64 time=0.033 ms
64 bytes from 10.1.1.2: icmp_seq=3 ttl=64 time=0.033 ms

Troubleshooting

• ip netns del test: delete the namespace test
• ip link delete veth0: delete the interface veth0

References

• https://developers.redhat.com/blog/2018/10/22/introduction-to-linux-interfaces-for-virtual-networking/#bridge: This article provided many beautiful illustrations.
• https://wiki.archlinux.org/index.php/Network_bridge: Arch Linux documentation is always useful and clear.
• https://blog.scottlowe.org/2013/09/04/introducing-linux-network-namespaces/: A gentle introduction.
• https://unix.stackexchange.com/questions/511783/for-veth-pair-ping-does-not-recognize-interface-name-and-tc-qdisc-netem-does-no
• Why assign MAC and IP addresses on Bridge interface
• Containers and networking