When first learning about IPv6, students are often surprised by the fact that IPv6 has another address type that is much different from the IPv4 address types that they are already familiar with: the link-local address. The caveat with these addresses is that they are only locally-significant (i.e., restricted to a single LAN broadcast domain) and are never used to source or receive communications across a layer-3 gateway. However, there is one less-popular address type that can be used for unicast communications on a confined LAN segment. The concepts of unicast, multicast, and broadcast and their accompanying addresses are familiar to IPv4 experts. Link-Local Addresses and Automatic Private IP Addressing (APIPA) However, sending an IPv6 packet to the all-nodes link-local multicast group address (FF02::1) comes close to that functionality. IPv6 networks will never use broadcasts on a LAN. On the other hand, IPv6 doesn’t use the broadcast method of packet delivery so there is no equivalent IPv6 address type. Broadcast packets are sent out all Ethernet switch ports, regardless of whether or not there are any hosts on the attached segments that need or want the broadcasted messages.
#Convert mac address to ipv6 link local mac
Whether the packet’s destination address is 255.255.255.255 and intended for all hosts in the entire broadcast domain or a broadcast address limited to a specific subnet (e.g., 192.168.1.255), both are converted to an “all-ones” layer-2 MAC address FF:FF:FF:FF:FF:FF.
Only IPv4 has broadcast as a method of sending one packet to ALL nodes on the current LAN. An IPv6 multicast address for well-known link-local messages would start with “FF02” and you may recognize that FF02::1 is the all-nodes link-local multicast group address. IPv6 multicast addresses can be used for link-local LAN communications or they can be scoped for site-specific communications or even global use. After the “FF”, the next 4 bits of the address represents the flag value, and the following 4 bits of the address is the scope of the range of the multicast message. IPv6 multicast addresses start with the two most-significant hex digits “FF” and have the format FF00::/8.
IPv4 multicast addresses (historically referred to as Class D addresses) are within the 224.0.0.0/4 range. Many people are familiar with how multicast addresses are used for one-to-many communications. This is also a topic that we discuss in our IPv6 COE Podcast #3. Please also read Tom Coffeen’s eloquent blogs ( part 1 and part 2) on “3 Ways to Ruin Your Future Network with IPv6 Unique Local Addresses”. You are encouraged to read RFC 4864, Local Network Protection for IPv6, to learn about why you do not need private addresses for your internal networks and why you subsequently do not need NAT for IPv6. However, with IPv6, beginners discover that FD00::/8 Unique Local Addresses (ULAs) exist for private network addressing, although their use is not generally recommended.
#Convert mac address to ipv6 link local free
Regardless of whether your organization’s public IPv4 or global IPv6 addresses are provided by an RIR or your upstream ISP, they are free to be used to source and receive Internet communications. Public IPv4 addresses are familiar to most, so grasping IPv6’s global unicast addresses (GUA) (2000::/3) is straightforward.
It is relatively easy to grasp the concept that unicast addresses are used for one-to-one communications. This article builds upon the IPv6 newbie questions theme and covers a couple of the IPv6 addressing nuances that are often surprising to IPv6 neophytes (and sometimes IPv6 veterans, too!).įrequently Unicast, Sometimes Multicast, but Never Broadcast We then asked the question, “What are the typical questions you get when teaching an IPv6 class?” Frequently, IPv6 instructors field questions from their students about IPv6 link-local addresses and how they work. In a recent article, I wrote about some of the common questions that IPv6 novices sometimes ask.