I actually don't have firewalls set up on my devices that run Yggdrasil yet (please don't crack me). I haven't noticed any brute-force attacks on my SSH servers yet. Though I really should set up firewalls.

As for routing, I run my own node on a VPS, so all my edge devices are peered with that machine so routing is fine. Though when my machines are on the same network they automatically peer with each other directly.