The multihomed / multi-homed tag is for a single PC or server with multiple NICs connected to different networks or multiple vLans on a single NIC. Multiple NICs can present unique challenges and expose the sysAdmin to unexpected routing, even make a machine less secure.
The Multi-Homed tag is for questions involving a machine connected to different networks. Multiple NICs bonded together into the same broadcast domain most likely do not count as Multi-Homed. Firewalls are multi-homed, but often are designed from the ground up to not have the problems services and systems may have when connected to more than one network.
On multi-homed servers, UDP can cause more problems than TCP such as when choosing udp protocol for openvpn or likely DNS servers.
man --pager=cat openvpn | egrep -A 10 -i multihome
--multihome
Configure a multi-homed UDP server. This option needs to be used when a server has more than one IP address (e.g.
multiple interfaces, or secondary IP addresses), and is not using --local to force binding to one specific address
only. This option will add some extra lookups to the packet path to ensure that the UDP reply packets are always
sent from the address that the client is talking to. This is not supported on all platforms, and it adds more pro‐
cessing, so it's not enabled by default.
Notes:
• This option is only relevant for UDP servers.
• If you do an IPv6+IPv4 dual-stack bind on a Linux machine with multiple IPv4 address, connections to IPv4
addresses will not work right on kernels before 3.15, due to missing kernel support for the IPv4-mapped
case (some distributions have ported this to earlier kernel versions, though).
