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Broadband Subscriber Sessions User Guide
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{ "lLangCode": "en", "lName": "English", "lCountryCode": "us", "transcode": "en_US" }
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Maintaining DHCP Subscribers During Interface Delete Events

date_range 06-Dec-23

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.
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    [edit system services]
    user@host# edit subscriber-management
    
  2. Configure the router to support the maintain-subscriber feature.
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    [edit system services subscriber-management]
    user@host# edit maintain-subscriber
    
  3. Configure the router to enable the maintain-subscriber feature when an interface-delete event occurs.
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    [edit system services subscriber-management maintain-subscriber]
    user@host# set interface-delete
    

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.

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    [edit system services dhcp-local-server]
    user@host# set persistent-storage automatic
    

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.

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    [edit system processes dhcp-service]
    user@host# set persistent-storage file-name
    
  2. Specify a frequency to back up the file.
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    [edit system processes dhcp-service]
    user@host# set persistent-storage backup-interval hours
    

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

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[edit system processes dhcp-service]
user@host# set persistent-storage acx-local-server1-client-data backup-interval 8

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:

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    user@host>show dhcp server binding detail
    
  • To display DHCPv6 local server binding information for the DHCP maintain subscribers feature:

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    user@host>show dhcpv6 server binding detail
    
  • To display DHCP relay binding information for the DHCP maintain subscribers feature:

    content_copy zoom_out_map
    user@host>show dhcp relay binding detail
    
  • To explicitly log out a DHCP local server subscriber when the maintain subscriber feature is enabled:

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    user@host>clear dhcp server binding binding-type
    
  • To explicitly log out a DHCPv6 local server subscriber when the maintain subscriber feature is enabled:

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    user@host>clear dhcpv6 server binding binding-type
    
  • To explicitly log out a DHCP relay subscriber when the maintain subscriber feature is enabled:

    content_copy zoom_out_map
    user@host>clear dhcp relay binding binding-type
    
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