Configuring Arp Scanning And Fixed Arp; Configuration Restrictions And Guidelines - HP 5920 Series Configuration Manual

[SwitchB] vlan 10
[SwitchB-vlan10] arp detection enable
# Configure the upstream interface as a trusted interface. By default, an interface is an untrusted
interface.
[SwitchB-vlan10] interface ten-gigabitethernet 1/0/3
[SwitchB-Ten-GigabitEthernet1/0/3] arp detection trust
[SwitchB-Ten-GigabitEthernet1/0/3] quit
# Configure a static IP source guard binding entry on interface Ten-GigabitEthernet 1/0/2 for user
validity check.
[SwitchB] interface ten-gigabitethernet 1/0/2
[SwitchB-Ten-GigabitEthernet1/0/2] ip source binding ip-address 10.1.1.6 mac-address
0001-0203-0607 vlan 10
[SwitchB-Ten-GigabitEthernet1/0/2] quit
# Enable ARP packet validity check by checking the MAC addresses and IP addresses of ARP
packets.
[SwitchB] arp detection validate dst-mac ip src-mac
After the configurations are completed, Switch B first checks the validity of ARP packets received
on Ten-GigabitEthernet 1/0/1 and Ten-GigabitEthernet 1/0/2. If the ARP packets are confirmed
valid, the switch performs user validity check by using the static IP source guard binding entries
and finally DHCP snooping entries.

Configuring ARP scanning and fixed ARP

ARP scanning is typically used together with the fixed ARP feature in small-scale networks.
ARP scanning automatically creates ARP entries for devices in an address range. The device performs
ARP scanning in the following steps:
1. Sends ARP requests for each IP address in the address range.
2. Obtains their MAC addresses through received ARP replies.
3. Creates dynamic ARP entries.
Fixed ARP converts existing dynamic ARP entries (including those generated through ARP scanning) to
static ARP entries. This feature prevents ARP entries from being modified by attackers. Static ARP entries
can also be manually configured by the arp static command.

Configuration restrictions and guidelines

When you configure ARP scanning and fixed ARP, follow these guidelines:
• IP addresses in existing ARP entries are not scanned.
ARP scanning will 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 arp fixup command is a one-time operation. You can use this command again to convert the
•
dynamic ARP entries learned later to static.
Due to the limit on the total number of static ARP entries, some dynamic ARP entries might fail the
•
conversion.
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