+ e ip route $ip_op default via 10.8.0.1 table 1
+
+ # on debian this is 0 (no filter), on ubuntu it\'s 1, which is no good. 0 or 2 both work fine.
+ # 2 drops it if the packet is not routable, martian address, or my default route is screwed up,
+ # so, eh, might as well. some rhel docs recommend using it.
+ e sysctl net.ipv4.conf.$tun_dev.rp_filter=2