Group-Specific DHCP Configurations

This topic describes guidelines to consider when configuring interface ranges for named interface groups for DHCP local server and DHCP relay. The guidelines refer to the following configuration statement:

• The start subunit, interface interface-name , serves as the key for the stanza. The remaining configuration settings are considered attributes.

• If the subunit is not included, an implicit .0 subunit is enforced. The implicit subunit is applied to all interfaces when autoconfiguration is enabled. For example, interface ge-2/2/2 is treated as interface ge-2/2/2.0.

• Ranged entries contain the upto option, and the configuration applies to all interfaces within the specified range. The start of a ranged entry must be less than the end of the range. Discrete entries apply to a single interface, except in the case of autoconfiguration, in which a 0 (zero) subunit acts as a wildcard.

• Interface stanzas defined within the same router or switch context are dependent and can constrain each other—both DHCP local server and DHCP relay are considered. Interface stanzas defined across different router (switch) contexts are independent and do not constrain one another.

• Each interface stanza, whether discrete or ranged, has a unique start subunit across a given router context. For example, the following configuration is not allowed within the same group because ge-1/0/0.10 is the start subunit for both.

• Two groups cannot share interface space. For example, the following configuration is not allowed because the three stanzas share the same space and interfere with one another—interface ge-1/0/0.26 is common to all three.

• Two ranges cannot overlap, either within a group or across groups. Overlapping occurs when two interface ranges share common subunit space but neither range is a proper subset of the other. The following ranges overlap:

• A range can contain multiple nested ranges. A nested range is a proper subset of another range. When ranges are nested, the smallest matching range applies.

  In the following example, the three ranges nest properly:

• Discrete interfaces take precedence over ranges. In the following example, interface ge-1/0/0.20 takes precedence and enforces an interface client limit of 5.

You can include the following statements at the [edit system services dhcp-local-server group group-name] hierarchy level to set group-specific DHCP local server configuration options. Statements configured at the [edit system services dhcp-local-server group group-name] hierarchy level apply only to the named group of interfaces, and override any global DHCP local server settings configured with the same statements at the [edit system services dhcp-local-server] hierarchy level.

DHCPv6 local server supports the same set of statements with the exception of the dynamic-profile statement.

• authentication —Configure the parameters the router sends to the external AAA server.

• dynamic-profile —Specify the dynamic profile that is attached to a group of interfaces.

• interface —Specify one or more interfaces, or a range of interfaces, that are within the specified group.

• liveness-detection —Configure bidirectional failure detection timers and authentication criteria for static routes, or Layer 2 liveness detection using ARP and Neighbor Discovery packets. For more information, see DHCP Liveness Detection Overview.

• overrides —Override the default configuration settings for the extended DHCP local server. For information, see Overriding the Default DHCP Local Server Configuration Settings.

• interface-tag—(Optional) Specifies a tag name for the interface that will be associated with a DHCP configuration. Use the tag to identify subscribers associated with this DHCP local server group.

You can include the following statements at the [edit forwarding-options dhcp-relay group group-name] hierarchy level to set group-specific DHCP relay agent configuration options. Group-specific statements apply only to the named group of interfaces, and override any global DHCP relay agent settings for the same statement.

Include the statements at the [edit forwarding-options dhcp-relay dhcpv6 group group-name] hierarchy level to configure group-specific options for DHCPv6 relay agent.

• active-server-group —Configure an active server group to apply a common DHCP relay agent configuration for a named group of DHCP server addresses. For information, see Configuring Active Server Groups to Apply a Common DHCP Relay Agent Configuration to Named Server Groups.

• authentication —Configure the parameters the router (or switch) sends to the external AAA server.

• dynamic-profile —Specify the dynamic profile that is attached to a group of interfaces.

• interface —Specify one or more interfaces, or a range of interfaces, that are within the specified group.

• liveness-detection —Configure bidirectional failure detection timers and authentication criteria for static routes, or Layer 2 liveness detection using ARP and Neighbor Discovery packets. For more information, see DHCP Liveness Detection Overview.

• overrides —Override the default configuration settings for the extended DHCP relay agent. For information, see Overriding the Default DHCP Relay Configuration Settings.

• relay-agent-interface-id —(DHCPv6 only) Insert the DHCPv6 Relay Agent Interface-ID option (option 18) in DHCPv6 packets destined for the DHCPv6 server.

• relay-agent-remote-id —(DHCPv6 only) Insert the DHCPv6 Relay Agent Remote-ID option (option 37) in DHCPv6 packets destined for the DHCPv6 server.

• relay-option —Configure selective processing, which uses DHCP options in client packets to identify and filter client traffic, and to specify the action DHCP relay agent takes with the traffic. For more information, see Using DHCP Option Information to Selectively Process DHCP Client Traffic.

• relay-option-82 —(DHCPv4 only) Enable or disable the insertion of option 82 information in packets destined for a DHCP server. For information, see Using DHCP Relay Agent Option 82 Information.

• service-profile —Specify the default subscriber service, (or default profile) which is activated when the subscriber (or DHCP client) logs in and no other service is activated by a RADIUS server or a provisioning server. For more information, see Default Subscriber Service Overview .

• interface-tag—(Optional) Specifies a tag name for the interface that will be associated with a DHCP configuration. Use the tag to identify subscribers associated with this DHCP relay agent.

The following example shows an extended DHCP local server configuration that includes optional pool matching and interface groups. This configuration specifies that the DHCP local server uses option 82 information to match the named address range for client IP address assignment. The option 82 matching must also be included in the address-assignment pool configuration. The DHCP local server uses the default pool match configuration of ip-address-first.