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Maintaining DHCP Subscribers During Interface Delete Events

Maintaining Subscribers During Interface Delete Events

You can configure the router to maintain DHCP subscribers (maintain the subscriber bindings) when an event occurs that normally results in the router deleting the subscriber. For example, by default, the router logs out DHCP subscribers when an interface delete event occurs, such as a line card reboot or failure. However, if you configure the router to maintain subscribers, the router identifies each subscriber that was on the deleted interface, and resumes normal packet processing for the subscriber when the interface is restored. This procedure does not maintain subscribers that are deleted during router reboots or failures.

Note:

Subscribers are logged off as usual when their lease expires, even If the router is configured to maintain subscribers and the subscriber is on a deleted interface that has not yet been restored.

You configure the router to maintain subscribers on a global basis—the configuration applies to DHCP local server, DHCPv6 local server, and DHCP relay clients in all logical routers and routing instances. When you enable the maintain subscribers feature, the router applies the feature to existing subscribers as well as subscribers who later connect.

If the maintain subscribers feature is enabled on the router, you can explicitly delete a subscriber binding and log out the subscriber by either specifying a lease expiration timeout or using one of the following commands, as appropriate:

Benefits of Maintaining Subscriber Bindings

Reduces the time to restore the subscriber session and minimizes loss of subscriber service.

Configuring the Router to Maintain DHCP Subscribers During Interface Delete Events

You can specify a configuration in which the router does not log out a subscriber when the subscriber’s interface is deleted.

Note:

This procedure does not maintain subscribers during router reboots or failures.

To configure the router to maintain DHCP subscribers when the subscriber interface is deleted:

  1. Specify that you want to configure subscriber management.
  2. Configure the router to support the maintain-subscriber feature.
  3. Configure the router to enable the maintain-subscriber feature when an interface-delete event occurs.

Configuring an ACX Series DHCP Local Server to Preserve Subscriber Binding Information

When an ACX series router functioning as a DHCP local server reboots, by default, all the subscriber binding information is lost. You can configure the local server to preserve the subscriber binding information to a file in /var/preserve. When the router reboots, the DHCP local server reads the file and restores the subscriber binding information and resumes normal packet processing for the subscriber. By default, a new file is generated every 24 hours from the commit time, but you can specify a backup interval of 1 through 48 hours. The configuration is a global setting for each routing instance.

To configure an ACX Series DHCP local server to store subscriber binding information:

  • Enable persistent storage.

To configure a file to store subscriber binding information:

  1. Specify a filename for storing subscriber binding information. By default, the file is named jdhcpd_client_data.
    Note:

    A commit error occurs if you try to configure the file with a name that is already present in the /var/preserve directory.

  2. Specify a frequency to back up the file.

The following example saves the binding information to /var/preserve/acx-local-server1-client-data every 8 hours:

See Also

Verifying and Managing DHCP Subscriber Binding During Interface Delete Events

Purpose

Display information related to the DHCP maintain-subscribers feature and explicitly log out maintained clients.

Action

  • To display DHCP local server binding information for the DHCP maintain subscribers feature:

  • To display DHCPv6 local server binding information for the DHCP maintain subscribers feature:

  • To display DHCP relay binding information for the DHCP maintain subscribers feature:

  • To explicitly log out a DHCP local server subscriber when the maintain subscriber feature is enabled:

  • To explicitly log out a DHCPv6 local server subscriber when the maintain subscriber feature is enabled:

  • To explicitly log out a DHCP relay subscriber when the maintain subscriber feature is enabled:

Related Documentation