# How to find arp states in freebsd (reachable,verify)? How arp reqeasts sent from freebsd ?



## Senthil (Apr 19, 2018)

How arp entry refresh happens during upper layer protocols connectivity time ?

Have verified arp reqeast not sent some cached neighbors (but those neighbors are connected ) ,how arp requests sent by freebsd ?


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## ShelLuser (Apr 19, 2018)

The arp(4) manualpage explains it all I think.


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## ronaldlees (Apr 20, 2018)

You might glean a little more information with the net-mgmt/arpwatch utility.  BTW: Welcome to the forum.


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## Senthil (Apr 25, 2018)

ronaldlees said:


> You might glean a little more information with the net-mgmt/arpwatch utility.  BTW: Welcome to the forum.



Thanks for your reply. Actually I need following details,

1 ) During upper layer protocols connections time, FreeBSD machines automatically sent unicast ARP requests (every two mins) to particular neighbor machine, but it's not happening for some neighbors.  .

2 ) So how ARP maintained in FreeBSD and how entries capable for FreeBSD ARP table .

Pls clarify on this .


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## ronaldlees (Apr 25, 2018)

The detail about how FreeBSD handles ARP is in the kernel code and specifically the network interface layer aspects.  It is implemented as part of the routing table. I'm not a kernel developer, but I know that a very good description for all of this can be found in the book "_Design and Implementation of the FreeBSD Operating System_" - a very good book BTW. I reference the book quite a bit. There are (at least) four or five pages in it that reference this topic, and a couple in pretty good detail. The implementation is not as straight-forward/simple as you might think (based on my lookup made just now). 

You could look at the source code and maybe find an answer to your question.  Barring that, you might ask your questions of a kernel or network layer developer on one of the FreeBSD mailing lists, since the developers themselves don't hang out here in quantity:

https://lists.freebsd.org/mailman/listinfo


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