What to do if I can't connect to OPNSense when connected to the LAN?

This troubleshooting guide describes when there is disrupted connection to OPNSense

Problem

I can’t connect to OPNSense. I was able to connect but after a restart I stopped getting assigned an IP Address via DHCP.

Background: I tried, to adjust the interface settings for the PLC Network to an DHCP behavior. After restarting the PC (to force new DHCP leases on the PLC Network) I stopped getting an IP address via the LAN Interface. I can still connect to the Proxmox layer but cannot identify any errors on the OPNSense VM.

Solution

  1. Kill the DHCP server

dhcpd[31998]: bad range, address 192.168.2.100 not in subnet 192.168.1.0 netmask 255.255.255.0

  1. Give the DHCP server an IP address outside of the actual IP range of the router. With this you crashed the DHCP server of the entire device (also for LAN). For example, it can be needed to set manually the IP to a LAN address and then change the DHCP range for PLC from 192.168.2.100 to 192.168.1.100
Last modified October 5, 2022: Historian article (#107) (5f30dc0)