It is very important to validate that the N2 bus is within specs as part of the planning for a N2 integration. The N2 bus is based on the RS-485 specification.
Some JCI N2 devices have a termination switch, others have a self termination capability. Research the JCI documentation carefully before assuming that the end of each N2 bus segment needs termination.
When you remove a legacy supervisory controller from the N2 bus it may have been providing termination that needs to be replaced to keep the bus operating within spec.