3com 8807 User Guide

C

HAPTER

 55: ARP C

ONFIGURATION

Normally, dynamic ARP takes effect and automatically searches for the resolution 
from the IP address to the Ethernet MAC address without the help of an 
administrator.

ARP entries used in Switch 8800 Family series routing switches include dynamic 
ARP entries and static ARP entries. Static entries are further divided into long static 
ARP entries and short static ARP entries.

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Dynamic ARP entries are automatically created and maintained by the ARP 
protocol through ARP packets. They can be discarded after the aging time 
expires, and updated by new ARP packets. They can also be overlaid by long 
static ARP entries and short static ARP entries. When the aging time expires, 
the port is disabled or the VLAN interface is disabled, dynamic ARP entries will 
be deleted.

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Static ARP entries are configured and maintained manually, including short ARP 
entries and long ARP entries.

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Long ARP entries contain all elements of an ARP entry. They can forward data 
directly. They cannot be aged, and overlaid by dynamic ARP entries.

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Short ARP entries are configured with IP addresses and MAC addresses only 
other than VLANs and egresses. They are generally used in users requiring IP 
address and MAC address binding. Its initial state is non-resolution, so it cannot 
forward data directly. It can resolve VLANs and egresses dynamically through 
ARP packets. A resolved static ARP entry can forward data and will not be 
aged. When the port and VLAN interface are disabled, a static ARP entry will be 
restored to the non-resolution state.

The ARP mapping table can be maintained dynamically or manually. Usually, the 
manually configured mapping from the IP addresses to the MAC addresses is 
known as static ARP. The user can display, add or delete the entries in the ARP 
mapping table through relevant manual maintenance commands.

The following sections describe static ARP configuration tasks:

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Perform the following configuration in system view.

Table 608   Manually add/delete static ARP mapping entries

Manually add a static ARP 
mapping entry 

arp static ip-address [ mac-address [ vlan-id { interface-type 
interface-number } ] [ vpn-instance vpn-instance-name ] ] 

Manually delete a static ARP 
mapping entry 

undo arp ip-address