Enabling Dhcp Starvation Attack Protection; Enabling Dhcp-Request Attack Protection - HP 6125XLG Layer 3-Ip Services Configuration Manual

Step
3. (Optional.) Manually save
DHCP snooping entries to the
file.
4. (Optional.) Set the amount of
time to wait after a DHCP
snooping entry changes
before updating the database
file.

Enabling DHCP starvation attack protection

A DHCP starvation attack occurs when an attacker constantly sends forged DHCP requests that contain
identical or different sender MAC addresses in the chaddr field to a DHCP server. This attack exhausts
the IP address resources of the DHCP server so legitimate DHCP clients cannot obtain IP addresses. The
DHCP server might also fail to work because of exhaustion of system resources. For information about the
fields of DHCP packet, see
Protect against starvation attacks in the following ways:
To relieve a DHCP starvation attack that uses DHCP requests encapsulated with different sender
•
MAC addresses, you can limit the number of MAC addresses that a Layer 2 port can learn by using
the mac-address max-mac-count command. For more information about the command, see Layer
2—LAN Switching Command Reference.
To prevent a DHCP starvation attack that uses DHCP requests encapsulated with the same sender
•
MAC address, perform this task to enable MAC address check for DHCP snooping. This function
compares the chaddr field of a received DHCP request with the source MAC address field in the
frame header. If they are the same, the request is considered valid and forwarded to the DHCP
server. If not, the request is discarded.
To enable MAC address check:
Step
1. Enter system view.
2. Enter interface view.
3. Enable MAC address check.

Enabling DHCP-REQUEST attack protection

DHCP-REQUEST messages include DHCP lease renewal packets, DHCP-DECLINE packets, and
DHCP-RELEASE packets. This function prevents the unauthorized clients that forge the DHCP-REQUEST
messages from attacking the DHCP server.
Command
dhcp snooping binding database
update now
dhcp snooping binding database
update interval seconds
"DHCP message format."
Command
system-view
interface interface-type interface-number
dhcp snooping check mac-address
74
Remarks
DHCP snooping entries are saved to
the database file each time this
command is executed.
The default setting is 300 seconds.
When a DHCP snooping entry is
learned or removed, the device does
not update the database file until
after the specified waiting period.
All changed entries during that
period will be updated.
Remarks
N/A
N/A
By default, MAC address
check is disabled.