I have two interfaces connected to a real machine, eth0 and vboxnet2 (a VirtualBox bridged network).
eth0 is sitting on 192.168.15.x and is connected to my ADSL modem. vboxnet2 is on 192.168.200.x.
Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface default 192.168.15.1 0.0.0.0 UG 0 0 0 eth0 192.168.15.0 * 255.255.255.0 U 1 0 0 eth0 192.168.200.0 * 255.255.255.0 U 0 0 0 vboxnet2
Should I be able to ssh from (say) 192.168.15.100 to 192.168.200.4? My understanding of the routing table is that it says "if you see any packets destined for 192.168.200.x, send them to the vboxnet2 interface". Doesn't seem like I need NAT, iptables magic, or bridged networking for that. But it isn't working ("No route to host").
Long time Linux user, but networking details have fallen off the mental stack in the last few years as NetworkManager started to do everything...