This example shows vxlan nat traversal, using UDP hole punching.

```
   +-------+
   | vxlan |
   +-------+
       | uplink
 +------------+
 | masquerade |
 +------------+
       |
   +-------+
   | vxlan |
   +-------+
```

Run
---
- `vagrant up`
- `python vxlan_hp.py` on node5 (`vagrant ssh node5`)
- `ping 192.168.5.5` from node2, node3

Limitations
-----------
UDP src port sent from inside of the NAT must be same with UDP dst port number, i.e. 4789 IANA assigned number.