Constant NEIGHBOR_CACHE_COUNT 

pub const NEIGHBOR_CACHE_COUNT: usize = raw::NEIGHBOR_CACHE_COUNT; // 8usize

Max neighbors the stack remembers, across all interfaces.

The cache holds the hardware address of each neighbor, learned from ARP or NDISC. When it is full, learning a neighbor evicts another one.

This is a limit with and without alloc. Default: 8.