In which situation is a DHCP snooping binding entry generated

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Information about generating DHCP snooping binding entries is as follows:

1. When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is not configured as a trust interface, users can go online, but no DHCP snooping binding entry is generated.
2. When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is configured as a trust interface, users can go online, but no DHCP snooping binding entry is generated.
3. When the dhcp snooping enable command is run on the user-side interface and the network-side interface is not configured as a trust interface, users cannot go online, but no DHCP snooping binding entry is generated.
4. When the dhcp snooping disable command is run on the user-side interface, users can go online, but no DHCP snooping binding entry is generated no matter whether the network-side interface is configured as a trust interface.
5. When the dhcp snooping enable command is run on the user-side interface and both user-side and network-side interfaces are configured as trust interfaces, users can go online, but no DHCP snooping binding entry is generated.

If the DHCP snooping function has been enabled but no DHCP snooping entry is generated, you can check device configuration in the preceding aspects.

Other related questions:
Generation of dynamic DHCP snooping binding entries on S series switch
Information about generating DHCP snooping binding entries is as follows: - When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is not configured as a trusted interface, users can go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is configured as a trusted interface, users can go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping enable command is run on the user-side interface and the network-side interface is not configured as a trusted interface, users cannot go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping disable command is run on the user-side interface, users can go online, but no DHCP snooping binding entry is generated no matter whether the network-side interface is configured as a trusted interface. - When the dhcp snooping enable command is run on the user-side interface and both user-side and network-side interfaces are configured as trusted interfaces, users can go online, but no DHCP snooping binding entry is generated. - If the DHCP snooping function has been enabled but no DHCP snooping entry is generated, you can check the device configuration in the preceding aspects.

Automatic backup of DHCP snooping binding table on S series switch
For S series switches in V200R003C00 and later versions, you can run the dhcp snooping user-bind autosave file-name [ write-delay delay-time ] command to enable automatic backup of the DHCP snooping binding table and specify the backup interval. By default, local automatic backup of the DHCP snooping binding table is disabled. By default, S series modular switches and fixed switches back up the DHCP snooping binding table every 1 hour and every 24 hours, respectively.

Number of supported static DHCP binding entries on S series switch
S series switches (except S1700 switches) support the static DHCP binding configuration. When configuring static DHCP binding, ensure that IP addresses to be bound exist in a DHCP address pool. If you want to know the maximum number of static DHCP binding entries that can be configured, send an email to e_online@huawei.com.

Static DHCP binding error on S series switch
For S series switches (except S1700 switches), if the message "Error: The static-MAC is exist in this IP-pool" or "Error: The IP address's status is error" is displayed when you configure a static DHCP binding entry, the configuration will fail. The failure occurs because the IP address to bind has been assigned to a client, and an internal mapping entry has already been created on the switch. In this case, you can run the reset ip pool { interface pool-name | name ip-pool-name } { start-ip-address [ end-ip-address ] | all | conflict | expired | used } command in the user view to manually reclaim the IP address in the address pool, and configure a new static binding entry.

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