I don't know anything about setting up DHCP, but the destination host unreachable part sounds like you're trying to connect to a system that is not on your subnet, and you don't have the route to that network in your routing table, or don't have a default gateway setup.
I'm used to simple Class C subnets, where the subnet mask is 255.255.255.0, so that without a gateway, I can directly contact everything on my subnet (i.e. 139.169.134.*). In the past, when I've gotten that error, it was because say I was trying to ping 184.108.40.206, well, it's on a different subnet, so it won't work unless I have a default route in the routing table to my gateway. Say my gateway is 220.127.116.11, I do this:
route add default gw 18.104.22.168
Once I've done that, now my packets will reach destinations outside my subnet, so long as the gateway address is actually a valid address for a working gateway
Hope this helps at least somewhat.