Guidelines for Configuring Interface Ranges

This topic describes guidelines that you should 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 keyword, 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 context are dependent and can constrain each other—both DHCP local server and DHCP relay are considered. Interface stanzas defined across different router 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.
  interface ge-1/0/0.10 upto ge-1/0/0.30interface ge-1/0/0.10
• 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 a common to all three.
  dhcp-relay group diamond interface ge-1/0/0.10 upto ge-1/0/0.30dhcp-local-server group ruby interface ge-1/0/0.26dhcp-relay group sapphire interface ge-1/0/0.25 upto ge-1/0/0.35
• 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:
  interface ge-1/0/0.10 upto ge-1/0/0.30interface ge-1/0/0.20 upto ge-1/0/0.40
• A range can contain multiple nested ranges. Nested ranges are ranges in which one 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:

  interface ge-1/0/0.10 upto ge-1/0/0.30interface ge-1/0/0.12 upto ge-1/0/0.15 excludeinterface ge-1/0/0.25 upto ge-1/0/0.29 exclude
• 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.
  interface ge-1/0/0.10 upto ge-1/0/0.30interface ge-1/0/0.15 upto ge-1/0/0.25 excludeinterface ge-1/0/0.20 overrides interface-client-limit 5

Related Topics

• Grouping Interfaces with Common DHCP Configurations