Common ARP Operations : Checking ARP entries

Latest reply: Jun 27, 2016 01:52:03 1651 1 0 0

In routine maintenance, you can run the display arp command in any view to check ARP entry information on the device.

By checking ARP entries on a gateway device, the network administrator can view information about the connected users, including IP addresses, MAC addresses, and interfaces. For example, the network administrator can check ARP entry information to query the MAC address based on the IP address of a user.

When the gateway does not learn the IP address of a connected user, the network administrator can ping the broadcast address on the network segment on the gateway. For example, if the gateway IP address is 10.10.10.1/24, the network administrator runs the ping 10.10.10.255 command on the gateway. Then the user on the same network segment sends an ARP Reply packet. After receiving the ARP Reply packet, the gateway can learn the user's IP address.

# Check ARP entries on the network segment 172.16.0.0/16.

<HUAWEI> display arp network 172.16.0.0 16
IP ADDRESS      MAC ADDRESS     EXPIRE(M) TYPE        INTERFACE   VPN-INSTANCE                                                      
                                          VLAN/CEVLAN                                                                               
------------------------------------------------------------------------------                                                      
172.16.10.3     0025-9efb-be55            S--         GE1/0/6
                                           100/-                                                                                    
172.16.20.3     0200-0000-00e8            S--         GE1/0/19
172.16.10.1     0025-9ef4-abcd            I -         Vlanif100                                                                    
172.16.10.2     0025-9efb-be55  20        D-0         GE1/0/6
                                           100/-                                                                                    
172.16.20.1     0025-9ef4-abcd            I -         GE1/0/19
172.16.20.2     0200-0000-00e8  18        D-0         GE1/0/19
------------------------------------------------------------------------------                                                      
Total:6         Dynamic:2       Static:2     Interface:2  
In the command output, the ARP entry of each row is described as follows:
  • The IP address is 172.16.10.3, MAC address is 0025-9efb-be55, and type is S (indicating a static ARP entry). For this static ARP entry, the outbound interface is GE1/0/6 and VLAN ID is 100.
  • The IP address is 172.16.20.3, MAC address is 0200-0000-00e8, and type is S (indicating a static ARP entry). For this static ARP entry, the outbound interface is GE1/0/19.
  • The IP address is 172.16.10.1, MAC address is 0025-9ef4-abcd, and type is I (indicating an interface ARP entry). This ARP entry indicates that 172.16.10.1 is the IP address of the interface VLANIF 100.
  • The IP address is 172.16.10.2, MAC address is 0025-9efb-be55, and type is D (indicating a dynamic ARP entry). This dynamic ARP entry is learned from the interface GE1/0/6, the VLAN ID is 100, and the remaining lifetime is 20 minutes.
  • The IP address is 172.16.20.1, MAC address is 0025-9ef4-abcd, and type is I (indicating an interface ARP entry). This ARP entry indicates that 172.16.20.1 is the IP address of the interface GE1/0/19.
  • The IP address is 172.16.20.2, MAC address is 0200-0000-00e8, and type is D (indicating a dynamic ARP entry). This dynamic ARP entry is learned from the interface GE1/0/19, and the remaining lifetime is 18 minutes.
Common ARP Operations : Checking ARP entries-1837869-1 NOTE:
If the value of MAC ADDRESS is Incomplete, the current ARP entry is a temporary one. When IP packets trigger ARP Miss messages, the device generates temporary ARP entries and sends ARP Request packets to the destination network segment.
  • When a temporary ARP entry is not aged out:
    • Before receiving an ARP Reply packet, the device discards the IP packets matching the temporary ARP entry, and no ARP Miss message is triggered.
    • After receiving the ARP Reply packet, the device generates a correct ARP entry to replace the temporary entry.
  • After the temporary ARP entry ages out, the device deletes this entry.

 

 

 


 

  • x
  • convention:

user_1763575
Created Jun 27, 2016 01:52:03 Helpful(0) Helpful(0)

Thank you.
  • x
  • convention:

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