Slave KDCs

Slave KDCs generate credentials for clients just like the master KDC. The slave KDCs provide backup in case the master is unavailable. Each realm should have at least one slave KDC. Additional slave KDCs might required, depending on these factors:

• The number of physical segments in the realm. Normally, the network should be set up so that each segment can function, at least minimally, without the rest of the realm. To do this requires a KDC to be accessible from each segment. The KDC in this instance could be either a master or a slave.

• The number of clients in the realm. Adding more slave KDC servers can reduce the load on the current servers.

It is possible to add too many slave KDCs. Remember that the KDC database must be propagated to each server, so the more KDC servers installed, the longer it can take to get the data updated throughout the realm. Also, since each slave retains a copy of the KDC database, more slaves increase the risk of a security compromise.

In addition, one or more of the slave KDCs can be configured to be swapped easily with the master KDC. The advantage to following this procedure on at least one of the slave KDCs is that if the master KDC fails for any reason, you will have a system preconfigured that will be easy to swap as the master. See "Swapping Master and Slave KDCs" for instructions on how to configure a swappable slave KDC.