Enabling Dhcp Starvation Attack Protection - H3C MSR 2600 Configuration Manual

To enable periodic refresh of dynamic relay entries:
Step
1. Enter system view.
2. Enable periodic refresh of
dynamic relay entries.
3. Configure the refresh
interval.

Enabling DHCP starvation attack protection

A DHCP starvation attack occurs when an attacker constantly sends forged DHCP requests using
different MAC addresses in the chaddr field to a DHCP server. This 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. The following methods are available to relieve or
prevent such attacks.
To relieve a DHCP starvation attack that uses DHCP packets encapsulated with different source
•
MAC addresses, you can limit the number of ARP entries that a Layer 3 interface can learn or MAC
addresses that a Layer 2 port can learn. You can also configure an interface that has learned the
maximum MAC addresses to discard packets whose source MAC addresses are not in the MAC
address table.
To prevent a DHCP starvation attack that uses DHCP requests encapsulated with the same source
•
MAC address, you can enable MAC address check on the DHCP relay agent. The DHCP relay
agent compares the chaddr field of a received DHCP request with the source MAC address in the
frame header. If they are the same, the DHCP relay agent forwards the request to the DHCP server.
If not, the relay agent discards the request.
Enable MAC address check only on the DHCP relay agent directly connected to the DHCP clients. A
DHCP relay agent changes the source MAC address of DHCP packets before sending them. If you
enable this feature on an intermediate relay agent, it might discard valid DHCP packet, and the sending
clients will not obtain IP addresses.
To enable MAC address check:
Step
1. Enter system view.
2. Enter the interface view.
3. Enable MAC address check.
Command
system-view
dhcp relay client-information refresh
enable
dhcp relay client-information refresh
[ auto | interval interval ]
Command
system-view
interface interface-type
interface-number
dhcp relay check mac-address
59
Remarks
N/A
By default, periodic refresh of
dynamic relay entries is
enabled.
By default, the refresh interval
is auto, which is calculated
based on the number of total
relay entries.
Remarks
N/A
N/A
By default, MAC address check
is disabled.