Configuring Arp Automatic Scanning And Fixed Arp; Configuration Guidelines - HP FlexFabric 5930 Series Security Configuration Manual

[SwitchB] interface fortygige 1/0/3
[SwitchB-FortyGigE1/0/3] dhcp snooping trust
[SwitchB-FortyGigE1/0/3] quit
# Enable ARP detection for VLAN 10.
[SwitchB] vlan 10
[SwitchB-vlan10] arp detection enable
# Configure the upstream interface as a trusted interface (an interface is an untrusted interface by
default).
[SwitchB-vlan10] interface fortygige 1/0/3
[SwitchB-FortyGigE1/0/3] arp detection trust
[SwitchB-FortyGigE1/0/3] quit
# Configure a static IP source guard binding entry on interface FortyGigE 1/0/2 for user validity
check.
[SwitchB] interface fortygige 1/0/2
[SwitchB-FortyGigE1/0/2] ip source binding ip-address 10.1.1.6 mac-address
0001-0203-0607 vlan 10
[SwitchB-FortyGigE1/0/2] 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, ARP packets received on interfaces FortyGigE 1/0/1 and
FortyGigE 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.

Configuring ARP automatic scanning and fixed ARP

ARP automatic scanning is usually used together with the fixed ARP feature in small-scale networks such
as a cybercafe.
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 convert existing dynamic ARP entries (including those generated through
ARP automatic scanning) to static ARP entries. The fixed ARP feature prevents ARP entries from being
modified by attackers. Static ARP entries can also be manually configured by the arp static command.

Configuration guidelines

When you configure ARP automatic scanning and fixed ARP, follow these guidelines:
IP addresses existing in ARP entries are not scanned.
•
ARP automatic scanning might 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 and converts existing dynamic ARP entries to static
•
ones.
The device has a limit on the total number of static ARP entries, including the manually configured
•
and the converted. As a result, some dynamic ARP entries might fail the conversion.
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