нейбор таблица это не арп таблица ....
В ядре Linux ARP cache и ND cache это одна структура, она называется neighbor table.
“struct neigh_table represents a neighboring table
(/include/net/neighbour.h)
The arp table (arp_tbl) is a neigh_table. (/include/net/arp.h)
In IPv6, nd_tbl (Neighbor Discovery table ) is a neigh_table also (include/net/ndisc.h)
There is also dn_neigh_table (DECnet ) (linux/net/decnet/dn_neigh.c) and clip_tbl (for ATM) (net/atm/clip.c)
gc_timer : neigh_periodic_timer() is the callback for garbage collection.
neigh_periodic_timer() deletes FAILED entries from the ARP table.”
https://wiki.linuxfoundation.org/networking/neighboring_subsystem