Configuring Dhcpv4 Class Of Service (Cos); Dhcpv6 Overview - Cisco ASR 9000 Series Configuration Manual

Configuring DHCPv4 Class of Service (CoS)

Configuring DHCPv4 Class of Service (CoS)
BNG supports manual reset of Class of Service (CoS) value of DHCPv4 control packets sent on subscriber
interfaces. By default, the outer and inner CoS values are set to 6. This feature allows to set or modify these
CoS values sent by BNG.
To reset the CoS values, use the dhcp ipv4 [inner-cos | outer-cos] value command.

DHCPv6 Overview

The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables DHCP servers to pass configuration
parameters, such as IPv6 network addresses, to IPv6 nodes. It enables automatic allocation of reusable network
addresses to the requesting clients, using the stateful address-configuration. Along with address and prefix
allocation, DHCPv6 also offers additional configuration flexibility by assigning other configuration parameters
such as DNS address, DNS domain name, AFTR address to IPv6 nodes in a network.
The basic DHCPv6 client-server concept is similar to using DHCP for IPv4 (DHCPv4). If a client wishes to
receive configuration parameters, it sends out a request on the attached local network to detect the available
DHCPv6 servers. Although DHCPv6 assigns IPv6 addresses or prefixes, name servers, and other configuration
information very similar to that of DHCP for IPv4, these are certain key differences between DHCPv4 and
DHCPv6. For example, unlike DHCPv4, address allocation in DHCPv6 is handled using a message option,
DHCPv6 clients can request multiple addresses and prefixes in a single request, and DHCPv6 can request
different lease times for the addresses and prefixes. These significant advantages of DHCPv6 make it a
preferred protocol for address assignment.
IPv6 hosts use Stateless Address Auto-Configuration (SLAAC), a model in which the hosts generate their
own addresses using a combination of local and router-advertised information.
The DHCPv6 has been standardized by the IETF through RFC 3315. This DHCPv6 protocol is a stateful
counterpart to IPv6 Stateless Address Auto-Configuration (RFC 4862), and can be used separately, or
concurrently with SLAAC, to obtain configuration parameters.
Note Prior to configuring DHCPv6, IPv6 must be enabled on the interface on which DHCPv6 is servicing and
enable Neighbor Discovery (ND).
For more information about Neighbor Discovery (ND), refer to the "Implementing Network Stack IPv4
and IPv6" section in the Cisco IOS XR IP Addresses and Services Configuration Guide.
Restrictions
• DHCPv6 Proxy supports to a maximum of eight external DHCPv6 servers per proxy profile.
• Bulk lease query is not supported.
• DHCPv6 server is supported only with BNG configuration.
Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,
Release 4.3.x
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Establishing Subscriber Sessions
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