# DHCPv6

DHCPv6 performs many of the functions performed by DHCP for IPv4 devices. As with DHCP for IPv4, an IPv6 interface can work as either a client or a server.

- As a DHCPv6 client, the interface can request (from a DHCPv6 server) delegation of long-lived prefixes across an administrative boundary. The server does not have to know the topology of targeted local network. For example, an ISP can use DHCPv6 to assign prefixes to downstream networks via downstream DHCPv6 clients. In addition, the interface can request (from a DHCPv6 server) the IP addresses of available DNS servers.

The interface can also request DNS search-list information. This list contains partial domain names, which assist DNS searches by concatenating entered usernames to the domain names.

- As a DHCPv6 server, the interface can provide all of these services to a downstream DHCPv6 client.

This page contains the following information:

Interface: Identifies the name of the interface.

DHCPv6 Service: Identifies the DHCPv6 service configured on the interface (Server or Client).

Configure: The following options might be available, depending on the device model or the service provided:

- Click Edit to configure DHCPv6 on an interface for the first time or to modify an existing configuration.

- Click DUID/Prefix Delegation List to create a new DUID.

Downstream Clients

On a downstream client (such as a CPE router), you can configure an interface as a DHCPv6 client and specify an Identity Association Prefix Delegation-Identification (IAPD-ID).

IAPD-ID Values

## IAPD-ID Settiings

An IAPD-ID is a positive integer that identifies a certain prefix on the server. The client can use this value to request a specific prefix from the server. If you specify a non-zero IAPD-ID value, it maps statically to a single prefix that has the same IAPD-ID on the server. If you specify a zero IAPD-ID value, or omit the value (which assigns it a zero value by default) the IAPD-ID maps it dynamically to a pool of prefixes on the server. The device treats all prefixes with a zero IAPD-ID as belonging to this pool.

You can identify a downstream client with a DUID (such as 00:03:00:01:aa:bb:cc:dd:ee:ff). This allows the client to request prefix delegation from the server.

SLA and TLA Values

## SLAs and TLAs

A Top-Level Aggregator (TLA) is the left most portion of an IPv6 address, which identifies the highest level in the routing hierarchy. The TLA usually specifies owned address space for an organization, such as an ISP. You specify the length of the TLA using the prefix length. The Site-Local Aggregator (SLA ) is a portion of an IPv6 address that identifies a network or subnet used by the organization. For example, a server might delegate the following prefix:

2001:908e:1::/32

where:

- TLA is 2001:908e

- SLA is 1

The same server might also delegate the following prefix:

2001:908e:2::/32

where:

- TLA is 2001:908e

- SLA is 2

Because each address has the same TLA, both belong to the same owned address space. However, because they have dissimilar SLAs, each delegated prefix maps to a different network.

To Configure a Prefix Assignment for a Downstream Client (Host Mode)

To configure an IAPD-ID value for a DHCPv6 client, perform the following steps.

1. On the DHCPv6 List page, click Edit for the interface you want to configure.

2. Enter the necessary information as described in DHCPv6 Client.

3. Click OK.

Upstream Routers

On an upstream router, you can configure an interface as a DHCPv6 server and specify two or more prefixes. The prefixes are then available for delegation to a downstream client (such as a CPE router). The interface can identify a downstream client with the DUID (such as 00:03:00:01:aa:bb:cc:dd:ee:ff). This allows the client to request prefix delegation from the server.

To Configure a DUID/Prefix Delegation for a Server (Router Mode)

To configure a DUID for an upstream server, perform the following steps.

1. On the DHCPv6 List page, click Edit for the interface you want to configure.

2. Enter the necessary information as described in DHCPv6 Server.

3. Click OK.