34.1.4 ARP
- <Structure of this section>
(1) Packet format of ARP
The formats and settings of ARP packets sent by the Switch conform to RFC826.
(2) ARP Packet-Validity Checking
The Switch checks the validity of received ARP packets. The following tables show the items checked for ARP packets.
|
ARP packet-field |
Check item |
When a check error occurs Packet discard |
|---|---|---|
|
Hardware type |
Hardware type = 1 (Ethernet) |
OK |
|
Protocol type |
Protocol =0800H(IP) |
OK |
|
Hardware address length |
Must be 6 |
OK |
|
Protocol address length |
Must be 4 |
OK |
|
Operation code |
1(REQUEST) Or 2 (REPLY) |
- |
|
Sender hardware address |
Not checked. |
OK |
|
Sender protocol address |
Must be one of the following
|
OK |
|
Target hardware address |
Not checked. |
- |
|
Target protocol address |
The value must be a value other than the following:
|
OK |
(Legend) OK: Discard-: Not applicable
(3) Operation in ARP Reception
The Switch learns new ARP entries or refreshes learned ARP entries based on received ARP packets. It also responds with ARP packets as needed. The following tables show the operations when ARP is received.
|
ARP type |
Target protocol address |
Sender protocol address |
ARP reply |
To learn new ARP |
ARP updating |
|---|---|---|---|---|---|
|
ARP Request |
Address of the local device |
0.0.0.0 |
OK |
- |
- |
|
Address of the local device |
- |
- |
- |
||
|
Other cases |
OK |
OK |
OK |
||
|
Other cases |
Address of the local device |
- |
- |
- |
|
|
Other cases |
- |
- |
OK |
||
|
ARP Reply |
Address of the local device |
0.0.0.0 |
- |
- |
- |
|
Address of the local device |
- |
- |
- |
||
|
Other cases |
- |
OK #1 |
OK |
||
|
Other cases |
Address of the local device |
- |
- |
- |
|
|
Other cases |
- |
- |
OK #2 |
(Legend) OK: Working-: Does not work
#1: Learn new when a ARP Reply is received for a ARP Request sent from the Switch.
#: When 2 ARP Reply is broadcast or multicast, ARP is updated.
(4) Aging timer
You can specify the aging time for ARP information for each interface in minutes. The minimum specifiable value is one minute and the maximum specifiable value is 24 hours. The default is four hours.
(5) ARP settings
To connect the Switch to a product that does not use the ARP protocol, use the arp configuration command to associate MAC addresses and IP addresses (the ARP information).
(6) Viewing ARP Info
You can execute the show ip arp command on an operation terminal to check the ARP information. By checking the ARP information, you can determine the association between the IP address and MAC address for a specific interface.