Some random IPv6 thoughts

Nearing the big test day and I'm brushing up on a few things.  IPv6 is one of them.

(NOTE:  I don't know how many other network engineers have the same problem, but until I deploy a technology a couple times, I really don't feel like I know it at all.  Memorizing this stuff is just tedious and difficult without the tactile portion of the technology, so I always struggle on these sorts of topics and require constant review)

OK, IPv6 addresses are 128-bit written in 8 sections of 4 hex characters each, separated by colons.  The first 64 bits are the "prefix" and contain the global routing information, provider class and the provider's sub-class.  The second 64 bits are the host ID.

Leading and contiguous zeros are able to be dropped off the address for ease of reading, and contiguous zeros can be replaced with a double-colon (or ::) but that can happen only once in an address.

IPv6 has no broadcast addresses, rather it uses multicast and anycast packets.  Multicast packets function similarly to the IPv4 multicast, while anycast packets will be responded to by the first node within the group.  Anycast would typically be used for load balancing.

Unicast packets in IPv6 are like the unicast packets in IPv4 - the packet has a specific destination.

Some common prefixes:

2000:: - Global unicast (Internet-routable)
FF02::1 - all nodes on the local network
FF02::2 - all routers
FF02::5 - OSPFv3 all routers
FF02::6 - OSPFv3 DR/BDR
FF02::9 - Ripng multicast
FF02::A - EIGRPv3

The last 64 bits of the address is the host identifier.  It is composed of the MAC address with FFFE inserted in the middle of it.  Then the U/L (Universal/Local) bit is inverted.  The U/L bit is the 7th bit from the left.