Sometimes, you just don't know what is on your network. A couple ways of finding out include using nmap or arp-scan.
An easy install:
sudo apt install arp-scan nmap
And an easy use with some basic defaults (the Unknown ones are LXC containers with manual mac addresses, and Cadmus Computer Systems is a VirtualBox device):
$sudo arp-scan --interface=vlan90 --localnet Interface: vlan90, datalink type: EN10MB (Ethernet) Starting arp-scan 1.9.5 with 256 hosts (https://github.com/royhills/arp-scan) 10.55.90.1 00:13:3b:0f:59:24 Speed Dragon Multimedia Limited 10.55.90.14 08:00:27:de:fc:9d Cadmus Computer Systems 10.55.90.21 0a:00:55:90:00:ab (Unknown) 10.55.90.22 0a:00:55:90:00:0c (Unknown) 10.55.90.23 0a:00:55:90:00:23 (Unknown) 10.55.90.31 f0:ad:4e:03:64:7f Globalscale Technologies, Inc. 8 packets received by filter, 0 packets dropped by kernel Ending arp-scan 1.9.5: 256 hosts scanned in 3.155 seconds (81.14 hosts/sec). 6 responded
With nmap, it knows about the mis-named mac:
$ sudo nmap -sn 10.55.90.0/24 Starting Nmap 7.70 ( https://nmap.org ) at 2018-09-29 20:25 MDT Nmap scan report for 10.55.90.1 Host is up (0.00032s latency). MAC Address: 00:13:3B:0F:59:24 (Speed Dragon Multimedia Limited) Nmap scan report for 10.55.90.14 Host is up (-0.10s latency). MAC Address: 08:00:27:DE:FC:9D (Oracle VirtualBox virtual NIC) Nmap scan report for 10.55.90.21 Host is up (-0.100s latency). MAC Address: 0A:00:55:90:00:AB (Unknown) Nmap scan report for 10.55.90.22 Host is up (-0.100s latency). MAC Address: 0A:00:55:90:00:0C (Unknown) Nmap scan report for 10.55.90.23 Host is up (-0.087s latency). MAC Address: 0A:00:55:90:00:23 (Unknown) Nmap scan report for 10.55.90.31 Host is up (0.00074s latency). MAC Address: F0:AD:4E:03:64:7F (Globalscale Technologies) Nmap scan report for 10.55.90.10 Host is up. Nmap done: 256 IP addresses (7 hosts up) scanned in 3.31 seconds
With these specific commands, arp-scan may see things which nmap may not, ie, firewall that are blocking pings. nmap probably has a mode for scanning similarly to arp-scan.