Can someone explain the various arp things
 

Hi,

I'm trying to do ip accounting, where user access is controlled by MAC.

ok , so I've got an accouting rule in the iptables by IP, as I don't appear to be able to mark by mac inbound AND outbound.

So I'm using arp to translate ip to MAC, and upload the statistics.

now arp -a appears to take a few seconds on each run.

Whats the difference between

cat /proc/net/arp
arp
arp -a

what's all the stuff about referesh cache etc ?

Does arp -a send out requests , and give you current status of connected MACs ?

Thanks

Ian