Configuring Defense Against Bogus DHCP Message Attacks
Context
If an attacker sends a bogus DHCP Request message to the DHCP server to extend the lease, the IP address cannot be released after the lease expires and authorized users cannot use the IP address. If the attacker forges a DHCP Release message of an authorized user and sends it to the DHCP server, the authorized user may be disconnected.
After a DHCP snooping binding table is generated, the device checks DHCP Request and Release messages against the binding table. Only DHCP messages that match entries are forwarded. This prevents unauthorized users from sending bogus DHCP Request messages or Release messages to extend the lease or to release IP addresses.
On a CE12800E, this function cannot be configured in the BD view.
Procedure
- Run system-view
The system view is displayed.
- You can enable the device to check the DHCP messages against the binding table in the system view, VLAN view, BD view or interface view.
- In the system view:
- In the VLAN view, BD view or interface view:
- Enable the trap function for DHCP snooping in the interface view.
- (Optional) Set the alarm threshold for the number of messages discarded by DHCP snooping in the system view or interface view.
- In the system view:
- In the interface view:
- Run commit
The configuration is committed.