Which port is the null port on that output?

Port "tun162d5c0de6a"
Interface "tun162d5c0de6a"
type: vxlan
options: {exts=gpe, key=flow, local_ip="10.0.1.91", remote_ip=flow}

Port "tun6f0e9979c0b"
Interface "tun6f0e9979c0b"
type: vxlan
options: {exts=gpe, key=flow, local_ip="10.0.1.91", remote_ip=flow}

I am surprised about that, I would think OVS would not allow to create two tunnel ports with the same parameters twice.

But the ovs really create two  tunnel ports and  one of the ports does not have the port number.

[root@wlz-controller odl]# ovs-vsctl show
e3894f29-cb8b-484e-a711-98411854e978
Manager "tcp:172.23.27.12:6640"
is_connected: true
Bridge br-int
Controller "tcp:172.23.27.12:6653"
fail_mode: secure
Port "tunad8b9653c61"
Interface "tunad8b9653c61"
type: vxlan
options: {exts=gpe, key=flow, local_ip="10.0.1.91", remote_ip=flow}
Port br-int
Interface br-int
type: internal
Port "tun9285edd6d47"
Interface "tun9285edd6d47"
type: vxlan
options: {exts=gpe, key=flow, local_ip="10.0.1.91", remote_ip=flow}
Port "tapc5d79335-8b"

[root@wlz-controller odl]# ovs-ofctl show -O Openflow13 br-int
OFPT_FEATURES_REPLY (OF1.3) (xid=0x2): dpid:0000fce6e8bafdd6
n_tables:254, n_buffers:256
capabilities: FLOW_STATS TABLE_STATS PORT_STATS GROUP_STATS QUEUE_STATS
OFPST_PORT_DESC reply (OF1.3) (xid=0x3):
1(tapc5d79335-8b): addr:b6:f7:6d:4a:92:84
config: PORT_DOWN
state: LINK_DOWN
speed: 0 Mbps now, 0 Mbps max
2(tunad8b9653c61): addr:c6:78:1c:b0:c4:4f
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
7(tap5000f882-28): addr:00:00:00:00:0c:51
config: PORT_DOWN
state: LINK_DOWN
speed: 0 Mbps now, 0 Mbps max
LOCAL(br-int): addr:fc:e6:e8:ba:fd:d6
config: PORT_DOWN
state: LINK_DOWN
speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (OF1.3) (xid=0x5): frags=normal miss_send_len=0

We can see through the command "ovs-vsctl show ",there is two tunnel ports. and  only one tunnel has the port number.

I don't know why it happens. The netvirt module can select the correct tunnel ports and write correct flow tables. I suspect it maybe caused by netvirt.