IPv6 provides a flexible addressing system that defines how each device is identified and reached within a Wi-SUN network. Understanding how IPv6 addresses are assigned and used is key to enabling mesh communication and upstream connectivity in Wi-SUN deployments.

The XBee Hive for Wi-SUN and XBee for Wi-SUN devices support 3 main types of IPv6 addresses:

Address type Purpose Scope Example

Link-local address

Local communication and neighbor discovery

Wi-SUN mesh interface

fe80::1234:abcd

Unicast address

Routed traffic within and beyond the mesh

Mesh and upstream networks

fd11::abcd, 2001:db8::1

Multicast addresses

Group messaging (e.g., RPL, NDP)

Link-local or realm-local

ff02::1, ff03::fc

A link-local address is used for communication between devices on the same local link — in this case, within the Wi-SUN mesh segment.

The XBee Hive for Wi-SUN and the XBee for Wi-SUN devices automatically generate link-local addresses at boot time.

These addresses always begin with the prefix fe80::/10 and are derived from the device’s MAC address via the EUI-64 method, as defined by the IPv6 standard. This ensures each interface has a stable and unique link-local identifier.

Link-local addresses are essential for:

  • Neighbor discovery.

  • Mesh routing control messages (RPL).

  • Local diagnostics and interface-scoped communication.

Link-local addresses are not routable beyond the local interface. They are used for discovery, mesh communication, and next-hop resolution within the mesh.

Unicast address

Unicast addresses enable end-to-end communication both within the mesh and between the Wi-SUN network and external IP systems.

The Border Router advertises an IPv6 prefix into the mesh, which can be:

  • A Unique Local Address (ULA), such as fd11::/64, used for private, internal networks.

  • A Global Unicast Address (GUA) allowing participation in the Internet.

Wi-SUN does not use Stateless Address Autoconfiguration (SLAAC). IPv6 addresses are assigned via DHCPv6, acting as the address authority for the Wi-SUN mesh.

Nodes then obtain their IPv6 addresses using DHCPv6 based on the advertised prefix. This address enables nodes to:

  • Communicate with external systems through the Border Router.

  • Be reached by other nodes within the mesh (if routing is configured).

  • Participate in end-to-end IPv6 communication across the network.

Multicast addresses

IPv6 multicast enables efficient one-to-many or many-to-many communication across a network. In Wi-SUN, multicast replaces the role of broadcast (which IPv6 does not support) and is heavily used by control-plane protocols such as:

  • RPL — for routing and topology maintenance

  • DHCPv6 — for address assignment and prefix dissemination

  • NDP — for neighbor discovery and link-layer reachability

The most commonly used multicast groups include:

Multicast address Purpose

ff02::1

All nodes on the local link

ff02::2

All routers on the local link

ff02::1a

RPL control messages (e.g., DIOs, managing mesh routing)

Devices automatically join the groups relevant to their role and use these multicast channels to exchange routing, addressing, and discovery messages that sustain the mesh.

Unlike unicast traffic, multicast in Wi-SUN is forwarded carefully to avoid flooding the mesh. Key characteristics include:

  • Multicast is generally limited in scope, typically to one link (using the ff02:: prefix).

  • Only routers forward multicast beyond their link, and only when explicitly configured.

  • Border Routers and mesh routers may suppress or aggregate some multicast traffic depending on role and configuration.

This controlled multicast behavior ensures efficient use of bandwidth while maintaining coordination across the Wi-SUN mesh.