Hirschmann RS20 User Manual page 58

Spanning Tree
If the device working as the root is inoperable and another device takes over
its function, the Max Age setting of the new root bridge determines the
maximum number of devices allowed in a branch.
Note: The RSTP standard dictates that all the devices within a network work
with the (Rapid) Spanning Tree Algorithm. If STP and RSTP are used at the
same time, the advantages of faster reconfiguration with RSTP are lost in the
network segments that are operated in combination.
A device that only supports RSTP works together with MSTP devices by not
assigning an MST region to itself, but rather the CST (Common Spanning
Tree).
Note: By changing the IEEE 802.1D-2004 standard for RSTP, the Standards
Commission reduced the maximum value for the "Hello Time" from 10 s to
2 s. When you update the switch software from a release before 5.0 to
release 5.0 or higher, the new software release automatically reduces the
locally entered "Hello Time" values that are greater than 2 s to 2 s.
If the device is not the RSTP root, "Hello Time" values greater than 2 s can
remain valid, depending on the software release of the root device.
UM Redundancy Configuration L2E
58
Release 7.1 12/2011