Configuring Arp Automatic Scanning And Fixed Arp; Configuration Guidelines - HP 6125G Configuration Manual

[SwitchB] arp detection validate dst-mac ip src-mac
# Configure port isolation.
[SwitchB] interface gigabitethernet 1/0/1
[SwitchB-GigabitEthernet1/0/1] port-isolate enable
[SwitchB-GigabitEthernet1/0/1] quit
[SwitchB] interface gigabitethernet 1/0/2
[SwitchB-GigabitEthernet1/0/2] port-isolate enable
[SwitchB-GigabitEthernet1/0/2] quit
After the preceding configurations are complete, ARP packets received on interfaces
GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 have their MAC and IP addresses checked
first, and then are checked against the static IP source guard binding entries and finally DHCP
snooping entries. However, ARP broadcast requests sent from Host A can pass the check on
Switch B and reach Host B. Port isolation fails.
# Configure ARP restricted forwarding.
[SwitchB] vlan 10
[SwitchB-vlan10] arp restricted-forwarding enable
[SwitchB-vlan10] quit
After the configuration, Switch B forwards ARP broadcast requests from Host A to Switch A
through the trusted port GigabitEthernet 1/0/3, and thus Host B cannot receive such packets. Port
isolation works normally.

Configuring ARP automatic scanning and fixed ARP

ARP automatic scanning is usually used together with the fixed ARP feature.
With ARP automatic scanning enabled on an interface, the device automatically scans neighbors on the
interface, sends ARP requests to the neighbors, obtains their MAC addresses, and creates dynamic ARP
entries.
Fixed ARP allows the device to change the existing dynamic ARP entries (including those generated
through ARP automatic scanning) into static ARP entries. The fixed ARP feature effectively prevents ARP
entries from being modified by attackers.
HP recommends that you use ARP automatic scanning and fixed ARP in a small-scale network such as a
cybercafe.

Configuration guidelines

Follow these guidelines when you configure ARP automatic scanning and fixed ARP:
IP addresses existing in ARP entries are not scanned.
•
• ARP automatic scanning may take some time. To stop an ongoing scan, press Ctrl + C. Dynamic
ARP entries are created based on ARP replies received before the scan is terminated.
The static ARP entries changed from dynamic ARP entries have the same attributes as the manually
•
configured static ARP entries.
Use the arp fixup command to change the existing dynamic ARP entries into static ARP entries. You
•
can use this command again to change the dynamic ARP entries learned later into static ARP
entries.
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