how to look inside gre tunnels ?

[Riccardo Veraldi]

Hello I am using argus to monitor teaffi on the OpenStack network node

of course I can see the gre traffic between network node and 
hypervisors, but hot to look what is passing insde the gre tunnel ?

thank you!

ra -r /var/log/argus/argus.out  - proto gre

          StartTime      Flgs  Proto            SrcAddr  Sport 
Dir            DstAddr  Dport  TotPkts   TotBytes State
    18:02:28.753615  *           gre     192.168.32.155 ->     
192.168.32.141               7       1416   INT
    18:02:43.048531  *           gre     192.168.32.155 ->     
192.168.32.141               1        384   REQ
    18:02:51.480639  *           gre     192.168.32.141 <->     
192.168.32.152               2        192   CON
    18:02:55.250461  *           gre     192.168.32.155 ->     
192.168.32.141               1        384   REQ
    18:02:56.486193  *           gre     192.168.32.141 <->     
192.168.32.152               2        168   CON
    18:03:08.237235  *           gre     192.168.32.141 ->     
192.168.32.151               1         96   INT
    18:03:11.598985  *           gre     192.168.32.155 ->     
192.168.32.141               7       1416   REQ
    18:03:13.244984  *           gre     192.168.32.141 <->     
192.168.32.151               2        168   CON
    18:03:18.388452  *           gre     192.168.32.155 ->     
192.168.32.141               2        768   REQ
    18:03:30.587969  *           gre     192.168.32.141 <->     
192.168.32.153               3        360   CON
    18:03:35.596982  *           gre     192.168.32.141 <->     
192.168.32.153               2        168   CON
    18:03:36.072892  *           gre     192.168.32.155 ->     
192.168.32.141               1        384   REQ
    18:03:51.887398  *           gre     192.168.32.141 <->     
192.168.32.153            5734    6351860   CON
    18:03:55.790966  *           gre     192.168.32.152 <->     
192.168.32.141               2        264   CON
    18:03:55.898084  *           gre     192.168.32.155 ->     
192.168.32.141               6       1284   REQ
    18:04:00.806343  *           gre     192.168.32.152 <->     
192.168.32.141               2        168   CON
    18:04:00.806804  *           gre     192.168.32.141 <->     
192.168.32.153            5056    6196176   CON
    18:04:01.022460  *           gre     192.168.32.155 ->     
192.168.32.141               2        516   REQ
    18:04:05.820967  *           gre     192.168.32.141 <->     
192.168.32.153               8        930   CON
    18:04:09.979538  *           gre     192.168.32.155 ->     
192.168.32.141               1        384   REQ
    18:04:18.295011  *           gre     192.168.32.155 ->     
192.168.32.141               1        384   REQ
    18:04:18.792758  *           gre     192.168.32.152 <->     
192.168.32.141               2        264   CON