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Group-Specific DHCP Configurations

You use the group feature to group a set of interfaces and then apply a common DHCP configuration such as extended DHCP local server, DHCPv6 local server, DHCP relay agent, and DHCPv6 relay agent to the named interface group. For more information, read this topic.

Guidelines for Configuring Interface Ranges for Groups of DHCP Interfaces

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.

Configuring Group-Specific DHCP Local Server Options

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.

Configuring Group-Specific DHCP Relay Options

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.

Configuring DHCP Server Configuration with Optional Pool Matching Using Groups

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.