pfSense

Currently pfSense cannot serve dual homed machine on DHCP without giving both interfaces a default gateway as leaving the default gateway field empty means pfSense will send the firewall interface as default gateway. As jimp suggested either a checkbox to suppress sending a gateway or entering the word "none" into the gateway box to prevent the gateway from being supplied to clients will be an easy and adequate solution for dual or multi homed machines. More information can be found on: https://forum.netgate.com/topic/52221/how-to-configure-dhcp-server-to-not-assign-a-default-gateway