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Cisco 300 Series

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ARP

The device maintains an ARP (Address Resolution Protocol) table for all known devices that reside in the IP subnets directly connected to it. A directly-connected IP subnet is the subnet to which an IPv4 interface of the device is connected. When the device is required to send/route a packet to a local device, it searches the ARP table to obtain the MAC address of the device. The ARP table contains both static and dynamic addresses. Static addresses are manually configured and do not age out. The device creates dynamic addresses from the ARP packets it receives. Dynamic addresses age out after a configured time.

NOTE     In Layer 2 mode, the IP, MAC address mapping in ARP Table is used by the device to forward traffic originated by the device. In Layer 3 mode, the mapping information is used for Layer 3 routing as well as to forward generated traffic.

To define the ARP tables:

  1. Click IP Configuration > IPv4 Management and Interfaces > ARP.
  2. Enter the parameters.
    • ARP Entry Age Out—Enter the number of seconds that dynamic addresses can remain in the ARP table. A dynamic address ages out after the time it is in the table exceeds the ARP Entry Age Out time. When a dynamic address ages out, it is deleted from the table, and only returns when it is relearned.
    • Clear ARP Table Entries—Select the type of ARP entries to be cleared from the system.
      • All—Deletes all of the static and dynamic addresses immediately.
      • Dynamic—Deletes all of the dynamic addresses immediately.
      • Static—Deletes all of the static addresses immediately.
      • Normal Age Out—Deletes dynamic addresses based on the configured ARP Entry Age Out time.
  3. Click Apply. The ARP global settings are written to the Running Configuration file.
  4. The ARP table displays the following fields:

    • Interface—The IPv4 Interface of the directly-connected IP subnet where the IP device resides.
    • IP Address—The IP address of the IP device.
    • MAC Address—The MAC address of the IP device.
    • Status—Whether the entry was manually entered or dynamically learned.
  5. Click Add.
  6. Enter the parameters:
    • IP Version—The IP address format supported by the host. Only IPv4 is supported.
    • VLAN—In Layer 2, displays the management VLAN ID.

    For devices in Layer 2 mode, there is only one directly-connected IP subnet, which is always in the management VLAN. All the static and dynamic addresses in the ARP Table reside in the management VLAN.

    Interface—For devices in Layer 3 system mode, an IPv4 interface can be configured on a port, LAG or VLAN. Select the desired interface from the list of configured IPv4 interfaces on the device.

    • IP Address—Enter the IP address of the local device.
    • MAC Address—Enter the MAC address of the local device.
  7. Click Apply. The ARP entry is saved to the Running Configuration file.