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# 1.2.4.1.2 Address Resolution Protocol (ARP) Configurations

ARP Specific User Configurations

- Number of Cache Entries:

  - Default number of entries per interface.
  - Default value 5
  - Symbol TCPIP_ARP_CACHE_ENTRIES

- Enable ARP Commands:

  - Enable the ARP TCP/IP Console Commands
  - Default value: false
  - Symbol: TCPIP_ARP_COMMANDS_ENABLE

- Delete Old Cache:

  - On initialization, delete the old cache if still in place
  - Else do not re-initialize
  - Default value: 1
  - Symbol TCPIP_ARP_CACHE_DELETE_OLD

- Time-Out for removal of Solved Entry (in sec):

  - Timeout for a solved entry in the cache.
  - The entry will be removed if the tmo elapsed and the entry has not been referenced again
  - Value is in seconds
  - Default value: (20 * 60)
  - Symbol TCPIP_ARP_CACHE_SOLVED_ENTRY_TMO

- Time-Out to solve Pending Cache Entry (in sec):

  - Timeout for a cache entry pending to be solved
  - The entry will be removed if the tmo elapsed and the entry has not been solved.
  - A solved entry moves to the solved entries timeout.
  - Value is in seconds
  - Default value: (1 * 60)
  - Symbol TCPIP_ARP_CACHE_PENDING_ENTRY_TMO

- Time-Out for Resending an ARP Request for Pending Entry (in sec):

  - Timeout for resending an ARP request for a pending entry
  - In order to prevent the ARP flooding the standard recommends it to be greater than 1 sec.
  - It should be less than TCPIP_ARP_CACHE_PENDING_ENTRY_TMO
  - Value is in seconds
  - Default value: 2
  - Symbol TCPIP_ARP_CACHE_PENDING_RETRY_TMO

- Number of Retries for Resolving an Entry:

  - Number of ARP requests generated for resolving an entry.
  - Default value: 3
  - Symbol TCPIP_ARP_CACHE_ENTRY_RETRIES

- Number of Retries for Gratuitous ARP Request:

  - Number of ARP requests generated when sending a gratuitous ARP probe.
  - Default value: 1
  - Symbol TCPIP_ARP_GRATUITOUS_PROBE_COUNT

- Purge Threshold Percentage:

  - Default purge threshold, percentage
  - Once the number of resolved entries in the cache gets beyond the threshold some resolved entries will be purged.
  - Default value: 75
  - Symbol TCPIP_ARP_CACHE_PURGE_THRESHOLD

- Number of Entries to Delete Once the Threshold is Reached:

  - The number of entries to delete, once the threshold is reached.
  - Default value: 3
  - Symbol TCPIP_ARP_CACHE_PURGE_QUANTA

- Maximum Percentage of Permanent Entries Allowed in Cache:

  - Maximum percentage of permanent entries in the cache.
  - Note that since permanent entries cannot be removed they tend to degrade the efficiency of the cache look up.
  - Default value: 50
  - Symbol TCPIP_ARP_CACHE_PERMANENT_QUOTA

- Alias Interfaces Share One Cache:

  - ARP caches configuration for aliases.
  - If this symbol is true, then the alias interfaces share the cache with the primary interface.
  - Otherwise each interface uses its own cache.
  - Default value should be 1 if the alias interfaces are in the same network with the primary interface
  - Symbol TCPIP_ARP_PRIMARY_CACHE_ONLY

- ARP Task Rate (in msec):

  - ARP task processing rate, in milliseconds.
  - The ARP module will process a timer event with this rate for maintaining its own queues, processing timeouts, etc.
  - Choose it so that the other ARP_CACHE_xxx_TMO are multiple of this
  - The lower the rate (higher the frequency) the higher the module priority and higher module performance can be obtained
  - The value cannot be lower than the TCPIP_STACK_TICK_RATE.
  - Default value: 2000
  - Symbol TCPIP_ARP_TASK_PROCESS_RATE