Introduction To Arp Detection - HP 4800G Series Configuration Manual

For information about DHCP snooping, refer to DHCP Configuration in the IP Services Volume.
For information about 802.1X, refer to 802.1X Configuration in the Security Volume.

Introduction to ARP Detection

The ARP detection feature allows only the ARP packets of legal clients to be forwarded.
Enabling ARP Detection Based on DHCP Snooping Entries/802.1x Security
Entries/Static IP-to-MAC Bindings
With this feature enabled, the device compares the source IP and MAC addresses of an ARP packet
received from the VLAN against the DHCP snooping entries, 802.1X security entries, or static
IP-to-MAC binding entries. You can specify a detection type or types as needed. If all the detection
types are specified, the system uses DHCP snooping entries first, then 802.1X security entries, and
then IP-to-MAC bindings. An ARP packet is considered valid only after it passes all types of ARP
detection; otherwise, it is considered as an attack and discarded.
1) After you enable ARP detection based on DHCP snooping entries for a VLAN,
Upon receiving an ARP packet from an ARP untrusted port, the device compares the ARP packet
against the DHCP snooping entries. If a match is found, that is, the parameters (such as IP address,
MAC addresses, port index, and VLAN ID) are consistent, the ARP packet passes the check; if not,
the ARP packet cannot pass the check.
Upon receiving an ARP packet from an ARP trusted port, the device does not check the ARP
packet.
If ARP detection is not enabled for the VLAN, the ARP packet is not checked even if it is received
from an ARP untrusted port.
ARP detection based on DHCP snooping entries involves both dynamic DHCP snooping entries and
static IP Source Guard binding entries. Dynamic DHCP snooping entries are automatically generated
through the DHCP snooping function. For details, refer to DHCP Configuration in the IP Service Volume.
Static IP Source Guard binding entries are created by using the user-bind command. For details, refer
to IP Source Guard Configuration in the Security Volume.
2) After you enable ARP detection based on 802.1X security entries, the device, upon receiving an
ARP packet from an ARP untrusted port, compares the ARP packet against the 802.1X security
entries.
If an entry with matching source IP and MAC addresses, port index, and VLAN ID is found, the ARP
packet is considered valid.
If an entry with no matching IP address but with a matching OUI MAC address is found, the ARP
packet is considered valid.
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