Inner VLAN ID setting for user packets on S series switch when the DHCP Option 82 field contains only one VLAN ID

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If the DHCP Option 82 field defined on an S series switch contains only one VLAN ID and specifies the inner VLAN ID value, the switch sets the inner VLAN ID of user packets to 4096.
Different carriers process invalid VLAN IDs in the DHCP Option 82 field in different ways. On a network, if the BRAS connected to the switch has specific requirements for invalid inner VLAN IDs in the DHCP Option 82 field, configure the Option 82 format that does not contain the inner VLAN ID.
To configure the Option 82 format, run the dhcp option82 format user-defined text command in the system view or interface view.

Other related questions:
Reasons why the Option 82 field in packets sent by other devices is replaced after the function of forcibly appending the Option 82 field is configured on S9700
S series switches support the Option 82 insertion function. The switch adds the configured Option 82 to received DHCP packets that do not contain the Option 82 field. If the packets received from other devices contain Option 82 fields, the switch deletes their original Option 82 fields and adds the configured Option 82 field to the packets.

Can I directly delete inner VLAN IDs from QinQ configuration
If the switch is running V100R005 or an earlier version, one or more inner VLAN IDs in QinQ cannot be directly deleted. You must delete the current selective QinQ configuration, and then reconfigure the inner VLAN IDs that do not need to be deleted. For example, the port vlan-stacking vlan 10 to 20 stack-vlan 100 command is configured on the switch. To delete inner VLAN 15, perform the following operations: Run the undo port vlan-stacking vlan 10 to 20 stack-vlan 100 command to delete the current selective QinQ configuration. Run the port vlan-stacking vlan 10 to 14 stack-vlan 100 and port vlan-stacking vlan 16 to 20 stack-vlan 100 commands to reconfigure the inner VLAN IDs that do not need to be deleted. If the switch is running a version later than V100R005, one or more inner VLAN IDs in QinQ can be directly deleted.

DHCP option 60 support
S series switches (except S1700 switches) support the Option 60 field of DHCP Request packets only when they function as DHCP clients.

Does ARP attack in one VLAN affect other VLANs on S series switch
On an S series switch, except S1700, when a VLAN suffers an ARP attack, such as ARP flood or ARP spoofing attack, the gateway cannot correctly learn ARP entries, causing a forwarding error. Packet forwarding in other VALNs is also affected. For example, when an ARP flood attack occurs in VLAN 10 (the gateway receives many ARP packets causing a high CPU usage), user services in other VLANs are affected.

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