Open-Mesh » batman-adv » batctl

I have test environment where thre Debian servers are connected to each other with help of access point in between (acting as layer 1/2 connectivity).
I have achived the layer 1 connectivity in within 3 servers after running batman commands , I see the batcl neighbours are up, alsp using batctl pin "neighbour mac address' i can ping the neighbor, But in output of "ip a" i see bat0 interface is down.
I am confused , what is the role of bat0 here, if it is down and still i can see batman-adv neighbours and ping.

oc@SugarOS:~$ sudo batctl n
[B.A.T.M.A.N. adv 2018.3, MainIF/MAC: ap0.20/00:22:4d:d8:cb:f8 (bat0/8e:de:d6:d7:18:9f BATMAN_IV)]
IF Neighbor last-seen
ap0.20 00:22:4d:d7:1e:10 0.320s
noc@SugarOS:~$ sudo batctl o
[B.A.T.M.A.N. adv 2018.3, MainIF/MAC: ap0.20/00:22:4d:d8:cb:f8 (bat0/8e:de:d6:d7:18:9f BATMAN_IV)]
Originator last-seen (#/255) Nexthop [outgoingIF] * 00:22:4d:d7:1e:10 0.156s (239) 00:22:4d:d7:1e:10 [ ap0.20]
noc@SugarOS:~$ sudo batctl ping 00:22:4d:d7:1e:10
PING 00:22:4d:d7:1e:10 (00:22:4d:d7:1e:10) 20(48) bytes of data
20 bytes from 00:22:4d:d7:1e:10 icmp_seq=1 ttl=50 time=2.45 ms
20 bytes from 00:22:4d:d7:1e:10 icmp_seq=2 ttl=50 time=3.04 ms
20 bytes from 00:22:4d:d7:1e:10 icmp_seq=3 ttl=50 time=1.75 ms
^C--- 00:22:4d:d7:1e:10 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss
rtt min/avg/max/mdev = 1.753/2.414/3.042/0.527 ms
noc@SugarOS:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1560 qdisc mq master ap0 state UP group default qlen 1000
link/ether 00:22:4d:d8:cb:f8 brd ff:ff:ff:ff:ff:ff
3: enp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:22:4d:d8:cb:f9 brd ff:ff:ff:ff:ff:ff
inet 172.28.252.38/24 brd 172.28.252.255 scope global dynamic enp3s0
valid_lft 3147sec preferred_lft 3147sec
inet6 fe80::222:4dff:fed8:cbf9/64 scope link
valid_lft forever preferred_lft forever
4: dongle0: <BROADCAST,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 06:37:b4:a1:fd:08 brd ff:ff:ff:ff:ff:ff
inet 10.254.1.220/29 brd 10.254.1.223 scope global dynamic dongle0
valid_lft 6093sec preferred_lft 6093sec
inet6 fe80::437:b4ff:fea1:fd08/64 scope link
valid_lft forever preferred_lft forever
5: cpe0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether 00:0e:8e:5d:23:59 brd ff:ff:ff:ff:ff:ff
6: ap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1560 qdisc noqueue state UP group default qlen 1000
link/ether 00:22:4d:d8:cb:f8 brd ff:ff:ff:ff:ff:ff
inet6 fe80::222:4dff:fed8:cbf8/64 scope link
valid_lft forever preferred_lft forever
7: ap0.20@ap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1560 qdisc noqueue master bat0 state UP group default qlen 1000
link/ether 00:22:4d:d8:cb:f8 brd ff:ff:ff:ff:ff:ff
inet 192.168.4.1/24 brd 192.168.4.255 scope global ap0.20
valid_lft forever preferred_lft forever
inet6 fe80::222:4dff:fed8:cbf8/64 scope link
valid_lft forever preferred_lft forever
8: bat0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether 8e:de:d6:d7:18:9f brd ff:ff:ff:ff:ff:ff
noc@SugarOS:~$