Static IPv6 Playground

This post is all about setting up an IPv6 environment for learning and testing of various setups and scenarios.

We will use network namespaces for our setup and proceed to define static IP addresses. (we will cover dynamic IP addresses in a following post)

Basic Setup

In order to prepare the ground for our IPv6 playground, we will use network namespaces to simulate different network stacks. A network namespace is an isolated network stack that includes interfaces, ip addresses and routes.

Throughout this post, we will use the ip command which is part of the iproute2 utilities.

Namespace creation

For our setup, we will use two namespaces: red & blue.

Lets create our two namespaces:

sudo ip netns add red
sudo ip netns add blue

Each namespace is created with a loopback interface which requires an explicit enablement:

sudo ip netns exec red ip link set lo up
sudo ip netns exec blue ip link set lo up

L2 connectivity (the veth)

In order to enable connectivity between the two namespaces, we will use a veth interface. A veth interface type comes always in pairs, anything that ingress one edge, egress the other edge and vice versa. It provides a L2 local connectivity between the peers.

We will create the veth interface at the root namespace and then place each peer in one of the namespaces.

Lets create the veth interface (and enable its links):

sudo ip link add veth00 type veth peer name veth10
sudo ip link set veth00 up
sudo ip link set veth10 up

And place each in the relevant namespace:

sudo ip link set dev veth00 netns red
sudo ip link set dev veth10 netns blue

At this point, assuming that IPv6 is enabled on the host, each namespace should show a loopback interface and another veth type interface which has a link-local IPv6 address.

Lets check the interfaces and their addresses:

$ sudo ip netns exec red ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
181: veth00@if180: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP
    link/ether 92:3a:37:75:36:40 brd ff:ff:ff:ff:ff:ff link-netnsid 1
    inet6 fe80::903a:37ff:fe75:3640/64 scope link
       valid_lft forever preferred_lft forever

$ sudo ip netns exec blue ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
180: veth10@if181: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP
    link/ether 8e:6a:6b:83:93:ea brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::8c6a:6bff:fe83:93ea/64 scope link
       valid_lft forever preferred_lft forever

L3 connectivity

With the IPv6 link-local addresses in place, we can already check the connectivity between the two namespaces.

Using the information gathered in the previous ip addr commands, learn the link-local IPv6 address of each peer and use it in the ping command.

Note: As the addresses have link-local scope, a zone must be added to the destination address. A link-local address has a default subnet of 64 bits with a default network address of fe80. Therefore, on a node with multiple interfaces, an explicit egress interface needs to be provided in order for the packet to know through which interface to exit. See here for more information about zones.

Lets run an IPv6 ping:

sudo ip netns exec red ping -6 fe80::<the-peer-last-64-bits-address>%veth00

IPv6 with global scope connectivity

The previous IPv6 link-local addresses may be used to check L3 connectivity between two directly connected peers (i.e. interfaces connected to the same physical LAN). Routers are required not to forward link-local addresses.

Therefore, in order to enable IPv6 connectivity beyond the physical LAN, a global scoped address needs to be defined on the interface. Such address may be set statically or dynamically.

IPv6 Global Static Address

In order to enable connectivity without a router, we need both peers to be set on the same network subnet, i.e. the network prefix need to be identical for both peers and the host part needs to be unique.

We will use a 64 bit network subnet with a network address of fd00. Resulting in the following addresses:

• red: fd00::11/64
• blue: fd00::22/64

Lets define a static address for each namespace:

sudo ip netns exec red ip addr add fd00::11/64 dev veth00
sudo ip netns exec blue ip addr add fd00::22/64 dev veth10

With this behind us, we can check the connectivity (without the zone part this time):

sudo ip netns exec red ping -6 fd00::22

Next we will explore dynamic IPv6.