Here are the simple steps to install SNMP in Ubuntu 18.04
Reference: https://support.auvik.com/hc/en-us/articles/204221884-How-to-enable-SNMP-on-Linux-based-servers-workstations
apt-get update && apt-get install snmp snmpd snmp-mibs-downloader
Next, using your text editor, edit /etc/snmp/snmpd.conf to look like this:
# this will make snmpd listen on all interfaces
agentAddress udp:161
# Or make it listen only to the local private network interface eg. eth0(192.168.100.3)
agentAddress udp:192.168.100.3:161
# a read only community ‘local’ and the source network* is defined
rocommunity local 172.17.1.0/16
Note: Make sure your firewall opens the port 161.
Restart the SNMP Daemon
service snmpd restart
Testing the SNMP service locally
snmpwalk -v 2c -c public localhost