post: Static IPv6 playground blog

Signed-off-by: Edward Haas <edwardh@redhat.com>

Author: EdDev

_posts/2020-05-03-static-ipv6-playground.md

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+---
+title: "Static IPv6 Playground"
+date: 2020-05-03
+categories:
+  - blog
+tags:
+  - ipv6
+---
+
+This post is all about setting up an IPv6 enviorment for learning and testing 
+of varios 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.
+
+Throught this post, we will use the `ip` command which is part of the
+[iproute2](https://wiki.linuxfoundation.org/networking/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](https://tools.ietf.org/html/rfc4291#page-11).
+
+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 infromation 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](https://tools.ietf.org/html/rfc4007) 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
+betweem 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 expore [dynamic IPv6](../dynamic-ipv6-playground).