Reasons why all IP and ARP packets are still discarded when DHCP snooping is not enabled on S series switch

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The function of checking IP and ARP packets is enabled on an interface. If this function is enabled, the IP and ARP packets cannot match entries in the binding table and are therefore discarded.

Other related questions:
Why are all IP packets and ARP packets still be discarded when DHCP snooping is disabled on a VLAN
This is because the function of checking IP and ARP packets is enabled on an interface. If this function is enabled, the IP and ARP packets cannot match the entries in the binding table and are therefore discarded.

On an S series switch enabled with DHCP snooping, the reason why the user cannot obtain the IP address after changing the terminal's location
On an S series switch enabled with DHCP snooping, a binding table is generated on the switch after a user obtains an IP address. If the user is switched to another interface of the device without releasing the IP address, the user cannot obtain the IP address or access the network. The corresponding binding table has been generated. The user attempts to apply for the same IP address with the same MAC address on a different interface. In this case, the switch does not know whether the user has switched to another interface or an unauthorized user attempts to access the network; therefore, the switch does not modify the binding table. As a result, the user fails to obtain the IP address and access the network. To solve this problem, you can delete the binding table from the switch.

Reasons why users cannot obtain IP addresses after DHCP Snooping is configured on S series switch
After DHCP snooping is enabled, all interfaces on S series switches are untrusted by default. DHCP Discover packets, however, must be forwarded from a trusted interface on the switch. Therefore, you must configure the interface connected to the DHCP server as a trusted interface to ensure that users connected to the switch can obtain IP addresses.

Reasons why IP packets matching binding entries are discarded a while after S series switch generates the dynamic binding table
After the dynamic binding table on the S series switches is generated for a while, If the IP packets that match the entries in the binding table are discarded, you need to check that the binding table still exists. The dynamic binding table has the aging time. If the IP address lease is not renewed after the aging time expires, the binding table ages out. As a result, the IP packets that match entries in the expired binding table are discarded.

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