Juniper JUNOSE SOFTWARE 11.2.X - BROADBAND ACCESS CONFIGURATION GUIDE 7-20-2010 Configuration Manual page 139

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as a DHCPv6 local server, to the requesting router, which is the customer premises
equipment (CPE) at the edge of the remote client site that acts as the DHCP client.
The DHCPv6 prefix delegation feature is useful in scenarios in which the delegating router
does not have information about the topology of the networks in which the customer
edge device or requesting router is located. In such cases, the delegating router requires
only the identity of the requesting router to choose a prefix for delegation. An IPv6 local
pool is configured on the delegating router, which contains information about the prefixes,
their validity periods, and other parameters to control their assignment to the requesting
routers. The delegating router is configured with a set of prefixes that is used to assign
to a CPE or DHCPv6 client, when it first establishes a connection with an Internet service
provider (ISP).
When the delegating router receives a request from a DHCPv6 client, it selects an available
prefix and delegates it to the client. The DHCPv6 client subnets the delegated prefix and
assigns the prefixes to links at the customer edge.
Keep the following points in mind when you configure IPv6 local address pools to assign
prefixes to requesting routers:
You must enable the IPv6 local address pool feature to be able to configure IPv6 local
address pools.
You can configure IPv6 local address pools for DHCP to allocate prefixes to client
requests that are received over PPP or non-PPP links, such as VLAN, S-VLAN, or
Ethernet.
You can configure multiple local address pools on a single virtual router, up to a
maximum of 500 pools per virtual router.
You can also configure multiple address pools on multiple virtual routers. Each IPv6
local address pool must have a unique name.
You can configure a valid and preferred lifetime for each IPv6 prefix, which determines
the length of time the requesting router can use the prefix.
You can configure multiple prefix ranges in an IPv6 local pool. The ranges can have
the same or different assigned prefix lengths.
You cannot configure overlapping prefix ranges in an IPv6 local pool. If you try to
configure a prefix range that overlaps with an existing prefix range in the IPv6 local
pool, an error message is displayed stating that the prefix range could not be configured.
Similarly, an error message is displayed if you try to configure a prefix range in an IPv6
local pool that overlaps with a prefix range in another IPv6 local pool on the same
virtual router.
You can configure certain prefix ranges to be excluded from being used for delegation
to the requesting router.
You can configure the IPv6 addresses of a primary and secondary DNS server in an
IPv6 local pool. The DNS server addresses are returned to the client in DHCPv6
responses as part of the DNS Recursive Name Server option.
Chapter 1: Configuring Remote Access
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