Content of /etc/ethers

[Steve Keller <keller.steve@gmx.de>]

Which tools read /etc/ethers, what do they expect in there, what do
they do with the contents?  Is it only used to show names to a user or
take names from a user instead of MAC addresses, like in tcpdump?

The Linux man page says the entries in /etc/ethers should be numeric
IP addresses or names which can be resolved by DNS, while the FreeBSD
man page says there should be fully qualified names in /etc/ethers
which should also be in /etc/hosts.

But does really some tool get a MAC address from somewhere, converts
it to a name using /etc/ethers, and then expects to resolve that name
into an IP address?

I would like to put names of hosts or interfaces in there, which don't
necessarily have an IP address or no entry in /etc/hosts or DNS, like
switches, access points or routers with multiple interfaces,
interfaces of a Linux bridge, etc.

And may the entry in /etc/ethers contain a '.' to separate a name and
an interface number or VLAN ID, like host.0 and host.1 for the LAN and
WLAN interface?

Steve