# Ringnode mirroring for Windows NT

For increased reliability, MDGMPORT.SYS can mirror two Ringnodes in a computer. This means that if one Ringnode in the pair fails the other can take over without any impact on the operating system (except for a possible change in performance if the pair is not symmetric).

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.