Unicast addresses

Unicast addresses provide one-to-one communication

Unicast addresses provide one-to-one communication.

Global

A Unicast global address identifies a single interface and is similar to an IPv4 public address.

Unicast global addresses are globally routable in the same manner as IPv4 addresses.

The following figure illustrates the Unicast global address parts.

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Unicast global address parts
Unicast global address parts
An IPv6 Unicast global address is composed of the following 3 levels:
  • public topology (48 bit Global Routing Prefix)

    • 001, specifies an IPv6 Unicast global address

    • Top Level Aggregation Identifier (TLA ID), the highest level in routing hierarchy

    • Res, reserved for future use

    • Next Level Aggregation Identifier (NLA ID), specifies a customer site

  • site topology (16 bit Subnet ID)

    • Site Level Aggregation Identifier (SLA ID); assigned within the site, an ISP cannot affect the SLA ID, enables up to 65,536 subnets within a site

  • interface ID (64 bits)

    • specifies the interface for a node on a subnet

The system uses the 48 bit global routing prefix for the route prefix exchange.

The IPv6 Prefix for Unicast global is 2000::/3 (RFC3513).

Link-local

Hosts on the same link/subnet use automatically configured IPv6 Unicast link-local addresses to communicate with each other.

Link-local addresses are automatically configured on all interfaces.

Routers do not forward packets containing a destination or source address with a link-local address.

IPv6 uses neighbor discovery (ND) for address resolution.

The IPv6 prefix for link-local Unicast addresses is FE80::/10 (RFC3513).

The following figure illustrates the parts of a Unicast Link-local address.

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Unicast Link-local address
Unicast Link-local address

Special addresses

The Unicast/special/unspecified address indicates the absence of an address and is the only valid SRC address for IPv6 Duplicate Address Detection (DAD).

Equivalent to the IPv4 unspecified address 0.0.0.0, represented as 0:0:0:0:0:0:0:0: or ::1; an IPv6 host that does not have a valid address uses the unspecified address as its source address when it sends a packet to discover whether an address is used by another node (during the boot process when the host requests address configuration information).

Note

Note

Do not assign an unspecified address, either statically or dynamically, to an interface.

The Unicast/special/loopback address is a special case Unicast address only found inside a single node.

The switch does not support the loopback address.

Equivalent to the IPv4 loopback address 127.0.0.1, represented as 0:0:0:0:0:0:0:1 or ::1; a node uses a loopback address to send a packet to itself.

The loopback address is beneficial in troubleshooting and testing the IP stack because you can use it to send a packet to the protocol stack without sending it onto the subnet.

Note

Note

Do not assign a loopback address, either statically or dynamically, to an interface.

Both Loopback and Unspecified addresses are not valid destination addresses.

An example of a unicast IPv6 address is 1080:0:0:0:8:8000:200C:417A

An example of a link-local Unicast IPv6 address is FE80::4445:4eff:fe54:1212