Configuring Arp Scanning And Fixed Arp; Configuration Restrictions And Guidelines - HPE FlexNetwork 5510 HI Series Security Configuration Manual

# Configure port isolation.
[SwitchB] port-isolate group 1
[SwitchB] interface gigabitethernet 1/0/1
[SwitchB-GigabitEthernet1/0/1] port-isolate enable group 1
[SwitchB-GigabitEthernet1/0/1] quit
[SwitchB] interface gigabitethernet 1/0/2
[SwitchB-GigabitEthernet1/0/2] port-isolate enable group 1
[SwitchB-GigabitEthernet1/0/2] quit
After the configurations are completed, Switch B first checks the validity of ARP packets
received on interfaces GigabitEthernet 1/0/1 and 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 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 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.
•
Due to the limit on the total number of static ARP entries, some dynamic ARP entries might fail
the conversion.
•
To delete a static ARP entry converted from a dynamic one, use the undo arp ip-address
[ vpn-instance-name ] command. Use the reset arp all command to delete all ARP entries or
the reset arp static command to delete all static ARP entries.
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