# Ringnode mirroring for Windows NT

The Windows NT driver MDGMPORT.SYS, incoporates support for Ringnode mirroring to provide a degree of fault tolerance. Ringnodes are mirrored in pairs, one being designated the Master and one the Slave. If the master Ringnode fails at any time, the driver closes it down and transparentky switches to using the standby. This switch is invisible to both the operating system and the other stations on the network.

Ringnode mirroring is controlled mainly by two parameters:

Instance Type - The default instance type is 'Standalone' which means that Ringnodes are not mirrored. If the instance type is set to 'Master', then this Ringnode will be the dominant one in the pair and NT will use its interface. The instance number of the master's 'Slave' Ringnode must be provided (see the next parameter) and an LAA must be given so that a slave can open onto the ring with the same address as its master. If the instance type is set to 'Slave', then this Ringnode will not open onto the ring unless a fault is detected with its master.

Slave Instance - Set this to the number in square brackets to the left of the slave Ringnode's entry in the list of Ringnodes in the network dialog box in Control Panel. If the slave Ringnode has not been installed yet, then set this parameter the instance number that will be allocated to the slave (usually the next unused number). The value can always be corrected after the slave is installed.

| You may experience difficulties when using PCI Ringnodes for mirroring on non-Intel platforms. If you are not running on an Intel platform, then we recommend that you do not use two PCI Ringnodes in a pair.

| If you are using one PCI Ringnode and one none-PCI Ringnode then we recommend that you install the PCI Ringnode as the master.