Arp Table; Configuring Arp; Configuring A Static Arp Entry - HP A5120 EI Series Configuration Manual

ARP table

After obtaining a host's MAC address, the switch adds the IP-to-MAC mapping to its own ARP table. This
mapping is used for forwarding packets with the same destination in the future.
An ARP table contains dynamic and static ARP entries.
Dynamic ARP entry
A dynamic entry is automatically created and maintained by ARP. It can age out, be updated by a new
ARP packet, and be overwritten by a static ARP entry. A dynamic ARP entry is removed when its age
timer expires or the interface goes down.
Static ARP entry
A static ARP entry is manually configured and maintained. It does not age out and cannot be overwritten
by a dynamic ARP entry.
Static ARP entries protect communication between devices, because attack packets cannot modify the IP-
to-MAC mapping in a static ARP entry.
Static ARP entries can be long or short.
 A long static ARP entry can be directly used to forward packets directly, because it includes not only
the IP address and MAC address, but also a configured VLAN and outbound interface.
A short static ARP entry includes only an IP address and a MAC address. It cannot be used to

forward data directly if the outbound interface is a VLAN interface. When a short static ARP entry
matches an IP packet to be forwarded, the switch sends an ARP request first. If the sender IP and
MAC addresses in the received ARP reply match the IP and MAC addresses of the short static ARP
entry, the switch adds the interface receiving the ARP reply to the short static ARP entry. Then the
entry can be used for forwarding IP packets.
NOTE:

Usually ARP dynamically resolves IP addresses to MAC addresses without manual intervention.

To allow communication with a host using a fixed IP-to-MAC mapping, configure a short static ARP entry for it.
To allow communication with a host using a fixed IP-to-MAC mapping through a specific interface in a specific
VLAN, configure a long static ARP entry for it.

Configuring ARP

Configuring a static ARP entry

A static ARP entry is effective when the device it corresponds to works normally. However, when a VLAN
or VLAN interface is deleted, any static ARP entry corresponding to it will also be deleted (if it is a long
static ARP entry) or will become unresolved (if it is a short and resolved static ARP entry).
Follow these steps to configure a static ARP entry:
To do...
Enter system view
Use the command...
system-view
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Remarks
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