Setup two vxlan boxes, verify the cumulative statistics for output while ping
One session ping:
```
root@:~ # ping -s 100 -c 4 10.10.20.0
PING 10.10.20.0 (10.10.20.0): 100 data bytes
108 bytes from 10.10.20.0: icmp_seq=0 ttl=64 time=0.922 ms
108 bytes from 10.10.20.0: icmp_seq=1 ttl=64 time=1.368 ms
108 bytes from 10.10.20.0: icmp_seq=2 ttl=64 time=1.299 ms
108 bytes from 10.10.20.0: icmp_seq=3 ttl=64 time=1.499 ms
--- 10.10.20.0 ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.922/1.272/1.499/0.214 ms
```
while another netstat:
```
root@:~ # netstat -w1 -I vxlan0
input vxlan0 output
packets errs idrops bytes packets errs bytes colls
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 142 1 0 142 0
0 0 0 142 1 0 142 0
0 0 0 142 1 0 142 0
0 0 0 142 1 0 142 0
0 0 0 0 0 0 0 0
```
The output bytes per ICMP request packet should be `ethernet(14) + IP(20) + ICMP(8) + payload(100) = 142`