18.1.4 Unicast address

(1) Link-local address

The upper 64 bits of the address prefix are fe80:: and the address including the 64-bit interface ID part is called IPv6 link-local address. IPv6 link-local addresses are valid only on a link and are used for address auto-configuration and neighbor discovery, and for networks without routers. When the source address or destination address of a packet is an IPv6 link-local address, the Switch does not forward the packet to other links.

Each interface that uses IPv6 on the Switch is assigned an IPv6 link-local address. You cannot assign multiple link-local addresses per interface. The following figure shows the format of an IPv6 link-local address.

(2) Site-local address

The upper 10 bits of the address prefix are 1111 1110 11, and the address including the 64-bit interface ID part is called IPv6 site-local address. The Switch treats IPv6 site-local address as IPv6 global address in "(3) Global address". Therefore, when you assign an IPv6 site-local address to an interface, configure routing or filtering so that the information about the IPv6 site-local address does not leave the site. The following figure shows the format of an IPv6 site-local address. Note that site-local addressing has been deprecated in RFC3879.

(3) Global address

Addresses whose higher 3 bits of the address prefix begin with 001 are called IPv6 global addresses. IPv6 global addresses are unique in the world and are used for traffic on the Internet. When the source address of a packet is an IPv6 global address, the packet is forwarded based on routing information. The following figure shows the format of an IPv6 global address.

(4) Unspecified address

The address 0:0:0:0:0:0:0:0 (0::0 or ::) with all bits at 0 is defined as an unspecified address. The unspecified address indicates that the interface has no address. This address is used when you start connecting to a node that is not assigned an address. You cannot intentionally assign the unspecified address to a node. The following figure shows the format of the unspecified address.

(5) Loopback address

The address 0:0:0:0:0:0:0:1 (0::1 or ::1) is defined as the loopback address. The loopback address is used as the destination address of a packet when the packet is sent to the local node. You cannot assign the loopback address to an interface. When the destination address of an IPv6 packet is the loopback address, the packet is not allowed to be sent to destinations other than the local node nor allowed to be forwarded by routers. The following figure shows the format of the loopback address.

(6) IPv4-compatible address

IPv4-compatible IPv6 addresses are used to allow two IPv6 nodes to communicate on an IPv4 routed network. An IPv4-compatible address is a special unicast address whose lower 32 bits contain an IPv4 address. The prefix is 96 bits, all bits of which are set to 0. The following figure shows the format of an IPv4-compatible address. Note that IPv4 compatible addressing is deprecated by RFC4291.

(7) IPv4 projection addressing

IPv4-mapped IPv6 addresses are used to communicate with IPv4-only nodes that do not support IPv6. When an IPv6 host needs to send packets to a host that only supports IPv4, the IPv6 host uses an IPv4-mapped IPv6 address. The prefix is 96 bits, the 80 upper bits of which are 0s and the remaining 16 bits are 1s. The following figure shows the format of an IPv4-mapped address.

(8) NSAP compatible addressing

This address format is used to convert an NSAP address so that it can be used in IPv6. To support NSAP, the upper 7 bits of the address format prefix are 0000 001. The following figure shows the format of an NSAP-compatible address. Note that NSAP compatible addressing is deprecated by RFC4048.

(9) IPX compatible addressing

This address format is used to convert an IPX address so that it can be used in IPv6. To support IPX, the upper 7 bits of the address format prefix are 0000 010. The following figure shows the format of an IPX-compatible address. Note that IPX compatible addressing is deprecated by RFC3513.

(10) 6to4 addressing

This address format is used for 6to4 tunneling. Configures IPv4 addressfor sites that are assigned the prefix 2002::/16 and that use tunneling from the 17th bit to the 48th bit. The following figure shows the format of a 6to4 address.

(11) IPv4 embedded IPv6 addressing

The address format used to translate IPv4 and IPv6 addresses. There are two forms, one using the well-known prefix as the prefix, and the other using any prefix. The Switch treats it as a normal global address.

The well-known prefix (64:ff9b::/96) format stores IPv4 addressing in the low-order 32-bits. The following diagram shows an IPv4 embedded IPv6 addressusing the well-known prefix.

(12) Discard prefix address

The address format used to discard packets at a specific source or destination address. The prefix is 100::/64. The Switch treats it as a normal global address. The following figure shows the discard prefix address.

(13) Teredo IPv6 addressing

This is the addressing format used by Teredo for IPv6 tunneling by UDP. 2001::/32 is assigned as the prefix. The Switch treats it as a normal global address. The following diagram shows Teredo IPv6 addressing.