Order Of Preference In Allocating Prefixes And Assigning Dns Addresses To Requesting Routers; Configuring The Dhcpv6 Local Address Pools - Juniper JUNOSE SOFTWARE 11.0.X - BROADBAND ACCESS CONFIGURATION GUIDE 4-1-2010 Configuration Manual

JUNOSe 11.0.x Broadband Access Configuration Guide
Order of Preference in Allocating Prefixes and Assigning DNS Addresses to Requesting
Routers
Prefix delegation can be configured at the interface level and at the router level. Also,
certain VSA attributes returned in the RADIUS Access-Accept message from the
authentication server can impact the selection of the prefix to be assigned to the
requesting router. The level of preference attached to each of these prefix delegation
configurations is crucial. The delegating router uses the following order of preference
to determine the source from which the DHCPv6 prefix is delegated to the requesting
router from the DHCPv6 server:
1.
2.
3.
If you configured a list of IPv6 DNS servers and a string of domain names in the IPv6
local address pool, the order of preference in returning the DNS server address or
domain name to the requesting client in the DHCPv6 response is as follows:

Configuring the DHCPv6 Local Address Pools

The IPv6 local address pool for DHCP is an object that contains information about
prefix configuration parameters and guidelines that govern the assignment of these
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Configuring the DHCPv6 Local Address Pools
If the interface address matches with any of the prefix ranges configured in the
IPv6 local address pool on the router, that pool is used to delegate the prefix to
the client.
An interface that is configured for prefix delegation is given priority over the
RADIUS attributes returned in the Access-Accept message or the prefixes
configured in the IPv6 local address pool on the delegating router.
The RADIUS server might return one or more of the following attributes in the
Access-Accept message in response to the client authentication request:
Ipv6-NdRa-Prefix (VSA 26-129)
Framed-IPv6-Prefix (RADIUS IETF attribute 97)
Delegated-IPv6-Prefix (RADIUS IETF attribute 123)
Framed-IPv6-Pool (RADIUS IETF attribute 100)
If any of the first three attributes are returned, then the prefix contained in those
attributes is used and the pool name in the Framed-IPv6-Pool attribute is ignored.
For example, if both the Delegated-IPv6-Prefix or Framed-IPv6-Prefix, and
Framed-IPv6-Pool attributes are returned from the RADIUS server, the DHCPv6
prefix delegation mechanism uses the Delegated-IPv6-Prefix attribute to advertise
the prefix to clients.
If prefix delegation is not configured at the interface level and if no prefix is
returned from the attribute in the RADIUS Access-Accept message, the prefix
configured in the IPv6 local pool is delegated to the requesting router.
Information returned from the RADIUS server for DNS servers only
Information from the pool
Locally configured DNS attributes