SSH using IPV6 getting error "No Route to Host" On My Mac Machine
If you want to perm a route in 10.10 Yosemite. here 

You should create a quick script with 

"#!/bin/bash" 

sudo /sbin/route add -net x.x.x.0/24 xxx.xxx.xxx.xxx

save it in a path 

chmod a+x the file

Then type this,.. 

sudo defaults write com.apple.loginwindow LoginHook /Path/To/Your/Script 

POW .. Yosemite perm route with edit file .