IPv6 cheat-sheet, part 3: IPv6 multicast
Many IPv6 multicast addresses are well-known to software implementing IPv6, to simplify common routing needs.
Notice: This blog post was originally published on Men&Mice before its acquisition by BlueCat.
The content reflects the expertise and perspectives of the Men&Mice team at the time of writing. While some references may be outdated, the insights remain valuable. For the latest updates and solutions, explore the rest of our blog
Now that we’ve familiarized ourselves with the IPv6 header and the IPv6 address space, let’s take a look at multicast.
Unicast, anycast, multicast
IPv6 packets can be sent, depending on the intended purpose, in a variety of ways:
- unicast: used for 1-to-1 communication; it sends the packet to a specific node. (Certain unicast addresses within the IPv6 address space are reserved. See the previous post for details.)
- anycast: used for 1-to-1-of-many communication; it sends the packet to multiple nodes but only intended to the closest on its route.
- multicast: used for 1-to-many communication; it sends the packet to multiple nodes.
We’re not covering anycast in detail at this moment, but we can — do let us know if that’s something of interest to you!
IPv6 multicast
IPv6 multicast works by nodes* joining multicast groups by sending Multicast Listener Discovery (MLD) report messages.
(*Little terminology from IETF: node is an interface enabled for IPv6. Router is any node that forwards IPv6 packets that are not expressly addressed to it. Host is any node that’s not a router.)
Multicast groups aren’t constrained by local or global (network) geography. Whether the host is on the local network or on the internet, as long as it’s signaling to join a multicast group, it can receive multicast packets sent to that group.
Any host can be a sender, whether it’s part of the multicast group or not. Only hosts part of the multicast group are receivers. Hosts can join or leave multicast groups dynamically at any time.
IPv6 multicast addresses: FF00::/8
All IPv6 multicast addresses share the prefix of FF00::/8.
- The first octet is FF (1111 1111). This way you can tell at a glance if an IPv6 address is intended for multicast or not.
- The second octet defines:
- the lifetime (0 for permanent multicast; 1 for temporary)
- and scope (1 for node, 2 for link, 5 for site, 8 for organization, and E for global scope).
The multicast address ends with the interface ID.
Well-known IPv6 multicast addresses
Many IPv6 multicast addresses are well-known to software implementing IPv6, to simplify common routing needs.
| Multicast Address | Description |
|---|---|
| ff02::1 | all nodes |
| ff02::2 | all routers |
| ff02::5 | all OSPF (Open Shortest Path First) routers |
| ff02::6 | all OSPF DRs (OSPF Designated Routers) |
| ff02::9 | all RIP (Routing Information Protocol) routers |
| ff02::a | all EIGRP (Enhanced Interior Gateway Routing Protocol) routers |
| ff02::d | all PIM (Protocol Independent Multicast) routers |
| ff02::f | UPNP (Universal Plug and Play) devices |
| ff02::11 | all homenet nodes |
| ff02::12 | VRRP (Virtual Router Redundancy Protocol) |
| ff02::16 | all MLDv2-capable routers |
| ff02::1a | all RPL (Routing Protocol for Low-Power and Lossy Networks) routers (used in Internet of Things (IoT) devices) |
| ff02::fb | multicast DNS IPv6 |
| ff02::101 | network time (NTP) |
| ff02::1:2 | all DHCP agents |
| ff02::1:3 | LLMNR (Link-Local Multicast Name Resolution) |
| ff02:0:0:0:0:1:ff00::/104 | solicited node address |
| ff02:0:0:0:0:1-2:ff00::/104 | node information query |
| ff05::1:3 | all DHCP server (site) |
| ff05::101 | all NTP server (site) |
(Did we or did we not promise a veritable smorgasbord of acronyms?)
Looking to Automate?
See our automation video playlist here.
More IPv6 coming up!
Next time we’ll be taking a look at IPv4-IPv6 tunneling and the particularities of migrating from IPv4 to IPv6.
After that, we have one last post to cover the remaining sections on our cheat-sheet, including useful Linux commands.
As always, do let us know if there’s a particular part of IPv6 (whether covered in here or not) you’d like to know more about!
Related content
Stay ahead of network issues with real-time metrics with BlueCat Integrity X
Get real-time DNS, DHCP, and IPAM metrics with BlueCat Integrity X. Detect issues early using native Prometheus telemetry and proactive DDI observability.
Adding business context to DDI with tagging in BlueCat Integrity X
Add business context to DNS, DHCP, and IPAM with tagging in BlueCat Integrity X. Improve visibility, automation, and governance across complex networks.
Security Insights for network security at the edge without complexity
For LiveWire and LiveNX users, analyze flow and packet telemetry for faster threat detection, stronger forensics, and shared visibility.
Network observability maturity stuck? Learn how to pull ahead
In EMA and BlueCat’s new report, learn about the five-stage Network Observability Maturity Model and how your enterprise can move along it.