IPv6 extension headers:
- Hop-by-hop options: signifies that the options need to be examined by each node of the packet
- Routing: list of intermidiate nodes that should be visited before the destination
- Fragment: signal when a packet has been fragmented by the source
- Destination options: examined only at the destination node, can appear twice
- Authentication header: used with IPsec to verify authenticity of a packet
- Encrypted Security Payload: used with IPsec, carries encrypted data for secure communication


IPv6 address types;
- Unicast: address defining interface or node
- Multicast: address defining a group of interfaces that might belong to different nodes
- Anycast: address for a group of interfaces, but unlike multicast, the anycast packet will travel to only 1 node (typically the nearest)

Unicast addresses support two types of scope; global & local (link-local & site-local)
Muticast support 16-types of scope.

Link-Local Unicast.

Link-local addresses are not routable and can be autogenerated.
Format: FE80::/10
Prefix (10-bit) zero (54-bit) interface ID (64-bit)

Site-local replace IPv4 RFC1918 and are not routable on the Internet

Global Unicast Addresses.


- format prefix: 001, aggregatable address assigned by IANA
- global routing prefix: hierarchical address allocation (ISPs, etc.)
- subnet-identifier: to subnet a site
- interface ID: to allow autoconfiguration

The interface ID is expressed in IEE EUI-64 format. Via router advertisements, a host can determine its subnet and auto-configure the interface. The IEEE EUI-id is the MAC address with 'FFFE' inserted in it.

Stateless autoconfiguration.

Allow IPv6 nodes to automatically assign an IPv6 address to a neighbor. Stateless autoconfiguration uses these elements;
- Router Advertisement message: sent to on-link hosts, periodically or in response to a Request Information in RA. Can include IPv6 prefix from router, routes, etc.
- Router sollicitation message: sent to discovrer presence and properties of on-link routers
- Prefix-list: contains prefixes the host can use for autoconfiguration

Pic will follow.

1. On startup, A & B generate link-local addresses.
2. Hosts send RS messages, theur link-local as source.
3. Router receives RS.
4. Router transmits RA, contains prefix-list.
5. Hosts use prefix for auto-config.

IPv6 multicast start with FF. There are three types;
- Solicited-node multicast are for Neighbor Solicitation messages
- All-nodes multicast-address are for RA-messages
- All-routers is for RS-messages

Completely random: OSPFv3 requires RID under [edit routing-options router-id]