A node is any device that has IPv6 implemented on at least one network interface. It can be a general purpose computer (desktop, notebook, tablet, etc). It can be a dedicated purpose device (temperature sensor, router, network connected consumer electronic device, etc). A node can be physical (actual hardware) or virtual (simulated in VirtualBox or VMWare).
A link is any communications medium (wired Ethernet, WiFi, VPN, PPP via modems, simulated internal network in VirtualBox, etc) that can connect two or more IPv6 nodes together at the Link Layer. An Ethernet LAN (including Ethernet cables and switches) is a typical link. The connection between the modem/router from your ISP and the ISP is another link (usually PPP). If you have WiFi router in your house, that creates yet another link (unless you are bridging your LAN to the WiFi system, in which case the Ethernet and WiFi combined are a single link). A link may have one or more /64 IPv6 address blocks valid on it. Two different links would have to have different /64 IPv6 address blocks – a single /64 address block cannot be present on more than one distinct link. A link can be physical (actual hardware) or virtual (simulated in VirtualBox as an “internal network”, or similar mechanisms in VMWare).
A network interface is any means of connecting a node to a link, that has the IPv6 protocol implemented on it. This could be via Ethernet, WiFi, USB or even RS-232. It can even be virtual (e.g. a tunnel endpoint or a network interface on a virtual node connected to a virtual link) or bridged to a physical link.
A router is a node that has two or more network interfaces, connected to two or more links, that has packet forwarding enabled between at least two of those links. It can be a dedicated hardware appliance, but can also be a general purpose node (Windows, FreeBSD, Linux, etc) that has multiple network interfaces and has enabled packet forwarding. It may also be running routing protocols (RIP, RIPng, etc) to dynamically update routing tables, but this is not required to be a router.
A host is a node that is not a router. It can still have multiple interfaces (e.g. Ethernet and WiFi, two interfaces connected to the same link, etc), so long as it is not doing packet forwarding between any pair of interfaces.
Required Addresses on a Host Node
The following IPv6 addresses are required to be on each Host node:
The loopback address (::1) for each interface. The loopback mechanism is actually its own isolated link that exists inside each interface. It has exactly one unicast address.
The required Link-Local Unicast address for each interface. This is normally automatically generated by the node. It is from the special IPv6 address block fe80::/64.
Any additional Unicast and Anycast addresses that have been assigned to any of the node’s interfaces. These addresses can be manually assigned or obtained automatically from SLAAC or DHCPv6.
The following All-Nodes multicast addresses:
Required Addresses on a Router Node
Since a router is a host that also does packet forwarding, it must recognize all of the above addresses listed for a host, as identifying itself. In addition, routers must also recognize the following addreses:
The Subnet-Router Anycast addresses for all interfaces on which it is configured to act as a router (any interfaces involved in packet forwarding). There is one of these addresses for each prefix advertised by an interface. The address consists of the advertised address prefix, followed by a suffix (Interface Identifier) of all zeros. For example, for the prefix 2001:470:3d:3000::/64, the Subnet Router Anycast address is 2001:470:3d:3000::/128. These Anycast addresses are automatically generated by the router.
All other Anycast addresses that have been assigned to any interface, by any means.
The following All-Routers multicast addresses:
Node Lawrence-pc (running Windows 7) has one Ethernet interface, connected to a single link. Therefore it is a host node.
Its MAC address is 50-46-5d-6b-7a-54. It has the Router Discovery option enabled (so it is doing SLAAC). It has the Randomize Identifiers option enabled (so it is not using EUI-64). It has the Temporary Addresses option disabled (it will not generate a temporary address for each advertised prefix).
Two prefixes are advertised on its link: 2001:470:3d:3000::/64 and fda4:73c2:e5b8:1000::/64. There is a stateful DHCPv6 server available, that manages the address pool 2001:470:3d:3000::4:0000/96.
This host will accept incoming packets whose destination address is any of the following:
The following addresses are assigned to it:
Router Example (6in4 tunneled IPv6)
Node fw1 is a Sixscape SolidGate firewall. SolidGate is based on FreeBSD. Firewalls are just fancy routers that have more sophisticated ways to filter traffic. It has two physical network interfaces, em0 (external) and em2 (internal). It also has one virtual interface, gif0 (6in4 tunnel endpoint). The external link (to IPv4-only ISP) has no IPv6 on it, so fw1 is not forwarding IPv6 packets between em0 and em2. Node fw1 is forwarding IPv6 packets between gif0 and em2. Therefore fw1 is an IPv6 router. It happens to be forwarding IPv4 packets between em0 and em2 network interfaces, so fw1 is also an IPv4 router.
em0, physical Etherrnet, connected to the external link (to IPv4-only ISP). Since this firewall connects to the IPv6 Internet via the gif0 tunnel instead of via the external interface, there is no IPv6 configured on the WAN interface (it is IPv4 only). It therefore has no IPv6 addresses, either unicast or multicast.
em2, physical Ethernet connected to the internal link (main company LAN). Its MAC address is 00:90:0b:1b:57:62. This interface does not have SLAAC enabled (all addresses are manually configured or happen automatically). It is running a Router Advertisement daemon, so it is a source of RA messages. It advertises two /64 address prefixes, 2001:470:3d:3000::/64 and fda4:73c2:e5b8:1000::/64 to the internal link.
This interface has the following Unicast addresses. Either can be used as a default gateway address by internal nodes.
fda4:73c2:e5b8:1000:: Subnet-Router Anycast for the ULA prefix
gif0, virtual, endpoint of 6in4 tunnel.
Tunnel endpoints are handled a little differently than regular interfaces. It has local and remote IPv4 addresses, as well as local and remote IPv6 addresses. The one on this firewall happens to be routing the entire 2001:470:3d:3000::/52 address block thorugh the tunnel.
Router Example (native IPv4 and IPv6)
Node vrouter1 is a homebrew virtual router created with FreeBSD 9.1, running in VirtualBox. It has two virtual network interfaces, em0 (external) and em1 (internal). Both the external link and internal link have native IPv4 and IPv6 on tham, and vrouter1 is forwarding IPv4 and IPv6 packets between interfaces em0 and em1. Therefore vrouter1 is a Dual Stack router.
em0 (external), virtual network interface bridged to the main physical LAN link. Its MAC address is 08:00:27:e0:f2:1f. This interface does not have SLAAC enabled (all addresses are manually configured or happen automatically).
This interface has the following Unicast addresses.
Since vrouter1 is a router, em0 has the following multicast addresses:
Note: ff01::2 (all routers in local interface) and ff05::2 (all routers in local site) were not found.
em1 (internal), virtual network interface, connected to virtual link “int1”. It is running a Router Advertisement daemon, so it is a source of RA messages. It advertises one /64 address prefix, 2001:470:3d:3001::/64.
It has the following Unicast addresses:
Either of these addresses can be used as a default gateway by internal nodes on virtual link “int1”. The link local is preferred.
It has Solicited Node Multicast addresses for each of the Unicast addresses:
Since vrouter1 is a router, em1 has the following multicast addresses: