Optimizing Dynamic ARP

Dynamic ARP is enabled without the need to be enabled. To optimize this function, you can modify some dynamic ARP parameters.

Context

If the device needs to update ARP entries frequently, reduce the aging timeout period of ARP entries and increase the aging detection frequency.

Procedure

Access the system view.
```
system-view
```

Access the interface view.

interface interface-type interface-number

Set a timeout period for aging dynamic ARP entries.
```
arp expire-time expire-times
```
By default, the aging timeout period is 1200 seconds.
Set the maximum number of ARP probe packets to be sent.
```
arp detect-times detect-times
```
The default value is 3.

Each time the aging time of a dynamic ARP entry elapses, the device sends an ARP probe packet to the peer device. If the device does not receive an ARP Reply packet from the peer device after sending a maximum number of probe packets, it deletes the ARP entry.

For example, the aging time of dynamic ARP entries is 60s, and the maximum number of ARP probe packets to be sent is 6. After 60s since an ARP entry is generated, the device sends an ARP probe packet every 5s. If the device does not receive any response after sending six ARP probe packets, it deletes the ARP entry. Therefore, the actual aging time of the ARP entry is 90s (60 + 6 x 5).

If the number of aging detection times is set to 0, the device deletes dynamic ARP entries immediately when the entries age.
Specify an interface to send an ARP aging detection packet in unicast mode.
```
arp detect-mode unicast
```
By default, an interface sends the last ARP aging detection packet in broadcast mode, and the rest ARP aging detection packets are sent in unicast mode.
Enable the multicast MAC address learning.
```
arp learning multicast enable
```
If the multicast MAC address learning function is disabled, the FW can learn only unicast MAC addresses from ARP packets.

Follow-up Procedure

Run the display arp interface command to view all ARP entries on an interface.

<sysname> display arp interface GigabitEthernet 0/0/2
IP ADDRESS      MAC ADDRESS     EXPIRE(M) TYPE   INTERFACE   VPN-INSTANCE
                                          VLAN/CEVLAN PVC
------------------------------------------------------------------------
192.168.1.11    0000-0a41-0201            I       GE0/0/2      
192.168.1.1     0000-0a41-0200  15        D       GE0/0/2     
-------------------------------------------------------------------------
Total:2         Dynamic:1       Static:0    Interface:1

If the TYPE field is I in an ARP entry, the entry contains the mapping between the local IP and MAC addresses of the interface. If the EXPIRE (M) field is null, the entry does not age. If the TYPE field is D, the entry is dynamically learned and ages in 15 minutes.