Configuring Arp Scanning And Fixed Arp; Configuration Restrictions And Guidelines - HP FlexFabric 5700 Series Security Configuration Manual

# 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
# Configure port isolation.
[SwitchB] port-isolate group 1
[SwitchB] interface ten-gigabitethernet 1/0/1
[SwitchB-Ten-GigabitEthernet1/0/1] port-isolate enable group 1
[SwitchB-Ten-GigabitEthernet1/0/1] quit
[SwitchB] interface ten-gigabitethernet 1/0/2
[SwitchB-Ten-GigabitEthernet1/0/2] port-isolate enable group 1
[SwitchB-Ten-GigabitEthernet1/0/2] quit
After the configurations are completed, Switch B first checks the validity of ARP packets received
on interfaces Ten-GigabitEthernet 1/0/1 and Ten-GigabitEthernet 1/0/2. If the ARP packets are
confirmed as valid, the switch performs user validity check by using the static IP source guard
bindings and 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.
# Enable ARP restricted forwarding.
[SwitchB] vlan 10
[SwitchB-vlan10] arp restricted-forwarding enable
[SwitchB-vlan10] quit
After the configuration is completed, Switch B forwards ARP broadcast requests from Host A to
Switch A through the trusted interface Ten-GigabitEthernet 1/0/3. Host B cannot receive such
packets. Port isolation works correctly.

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 automatic scanning and fixed ARP, follow these restrictions and 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.
370