Netgear XCM8806 Chassis User Manual - Page 457
Configuring ARP Learning, Adding a Permanent Entry to the ARP Table, Configuring DHCP Secured ARP
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NETGEAR 8800 User Manual Configuring ARP Learning As previously described, ARP learning is enabled by default. The switch builds its ARP table by tracking ARP requests and replies. To disable ARP learning on one or more ports in a VLAN, use the following command: disable ip-security arp learning learn-from-arp {vlan} ports [all | ] To re-enable ARP learning on one or more ports in a VLAN, use the following command: enable ip-security arp learning learn-from-arp {vlan} ports [all | ] Adding a Permanent Entry to the ARP Table If you disable ARP learning, you must either manually add a permanent entry to the ARP table or configure DHCP secured ARP to populate the ARP table. To manually add a permanent entry to the ARP table, use the following command: configure iparp add {vr } For more detailed information about this command and IP routing, see Chapter 20, IPv4 Unicast Routing. Configuring DHCP Secured ARP Another method available to populate the ARP table is DHCP secured ARP. DHCP secured ARP requires that ARP entries be added to or deleted from the ARP table only when the DHCP server assigns or re-assigns an IP address. These entries are known as a secure ARP entry. If configured, the switch adds the MAC address and its corresponding IP address to the ARP table as a permanent ARP entry. Regardless of other ARP requests and replies seen by the switch, the switch does not update secure ARP entries. DHCP secured ARP is linked to the "DHCP snooping" feature. The same DHCP bindings database created when you enabled DHCP snooping is also used by DHCP secured ARP to create secure ARP entries. The switch only removes secure ARP entries when the corresponding DHCP entry is removed from the trusted DHCP bindings database. Note: If you enable DHCP secured ARP on the switch without disabling ARP learning, ARP learning continues which allows insecure entries to be added to the ARP table. Before you configure DHCP secured ARP, you must enable DHCP snooping on the switch. To enable DHCP snooping, use the following command: enable ip-security dhcp-snooping {vlan} ports [all | ] violation-action [drop-packet {[block-mac | block-port] [duration | permanently] | none]}] {snmp-trap} For more information about DHCP snooping see, Configuring DHCP Snooping on page 448. Chapter 17. Security | 457
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