DNA Center or the devbox is not able to reach any network devices, the switches may be down or have a wrong IP etc
[root@devbox ~]# arp -na
? (10.10.20.254) at 00:00:0c:9f:f0:0b [ether] on ens192
? (10.10.20.84) at <incomplete> on ens192
? (10.10.20.251) at 28:6f:7f:b1:03:2c [ether] on ens192
? (10.10.20.81) at <incomplete> on ens192
? (10.10.20.82) at <incomplete> on ens192
? (10.10.20.83) at <incomplete> on ens192
