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

```
         +---------------+
         | (node5) vxlan |
         +---------------+
                  | uplink
       +--------------------+
       | (node4) masquerade |
       +--------------------+
                  |
         +--------+--------+
         |                 |
 +-------+-------+ +-------+-------+
 | (node2) vxlan | | (node3) 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.