Verifying the DHCP Binding Database

Purpose

Verify that the DHCP binding database reflects your DHCP server configuration.

Action

From operational mode in the CLI, to display all active bindings in the database, enter the show system services dhcp binding command. To display all bindings in the database, including their current binding state, enter the show system services dhcp binding detail command. To display more information about a client, including its DHCP options, enter the show system services dhcp binding ip-address detail command, replacing ip-address with the IP address of the client.

The DHCP binding database resulting from the configuration defined in Configuring the DHCP Server with a Configuration Editor is displayed in the following sample output.

To clear the DHCP binding database, enter the clear system services dhcp binding command. To remove a specific entry from the DHCP binding database, enter the clear system services dhcp binding ip-address command, replacing ip-address with the IP address of the client.

You can also use the J-Web interface to view information in the DHCP binding database. For more information, see Monitoring DHCP.

IP Address   Hardware Address   Type          Lease expires at
192.168.2.2  02:04:06:08:0A:0C  dynamic       2005-02-07 8:48:59 PDT
192.168.2.50 01:03:05:07:09:0B  static        never

    IP address           192.168.2.2
    Hardware address     02:04:06:08:0A:0C
    Pool                 192.168.2.0/24
    Request received on  fe-0/0/0

Lease information:
    Type                 DHCP
    Obtained at          2005-01-24 8:48:59 PDT
    Expires at           2005-02-07 8:48:59 PDT
    State                active

DHCP options:
    Name: domain-name, Value: mycompany.net mylab.net
    Name: name-server, Value: 192.168.10.2
    Code: 16, Type: ip-address, Value: 192.168.2.33

What it Means

Verify the following information:

• For each dynamic binding, verify that the IP address is within the range of the configured IP address pool. Under Lease Expires, verify that the difference between the date and time when the lease expires and the current date and time is less than the maximum configured lease time.
• For each static binding, verify that the IP address corresponds to the MAC address displayed under Hardware Address (as defined in the static-binding statement in the configuration). Under Lease Expires, verify that the lease expiration is never.
• In the output displayed by the show system services dhcp binding ip-address detail command, verify that the options under DHCP options are correct for the subnet.
• Verify that the show system services dhcp conflict command does not display any conflicts.

Related Topics

For complete descriptions of show system services dhcp binding and show system services dhcp conflict commands and output, see the JUNOS System Basics and Services Command Reference.