D-Link DGS-1210-12TS/ME User Manual page 77

4 Configuration
DGS-1210 series Metro Ethernet Managed Switch User Manual
and Multiple Spanning Tree Protocol (MSTP) as defined by the IEEE802.1 specification. RSTP can operate
with legacy equipment implementing IEEE 802.1D, however the advantages of using RSTP will be lost.
The IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) evolved from the 802.1D STP standard. RSTP was
developed in order to overcome some limitations of STP that impede the function of some recent switching
innovations. The basic function and much of the terminology is the same as STP. Most of the settings
configured for STP are also used for RSTP. This section introduces some new Spanning Tree concepts and
illustrates the main differences between the two protocols.
The IEEE 802.1 Multiple Spanning Tree (MSTP) provides various load balancing scenarios by allowing
multiple VLANs to be mapped to a single spanning tree instance, providing multiple pathways across the
network. For example, while port A is blocked in one STP instance, the same port can be placed in the
Forwarding state in another STP instance.
By default, Rapid Spanning Tree is disabled. If enabled, the Switch will listen for BPDU packets and its
accompanying Hello packet. BPDU packets are sent even if a BPDU packet was not received. Therefore,
each link between bridges is sensitive to the status of the link. Ultimately this difference results in faster
detection of failed links, and thus faster topology adjustment.
By default Multiple Spanning Tree is enabled. It will tag BPDU packets to receiving devices and distinguish
spanning tree instances, spanning tree regions and the VLANs associated with them.
After enabling STP, setting the STP Global Setting includes the following options:
Figure 4.98 - Configuration > Spanning Tree > STP Bridge Global Settings
STP State: Specify the Spanning Tree Protocol to be Enabled or Disabled.
STP Version: You can choose MSTP, RSTP or STP Compatible. The default setting is MSTP.
Bridge Priority: This value between 0 and 61410 specifies the priority for forwarding packets: the lower the
value, the higher the priority. The default is 32768.
TX Hold Count (1-10): Used to set the maximum number of Hello packets transmitted per interval. The
count can be specified from 1 to 10. The default is 6.
Maximum Age (6-40 sec): This value may be set to ensure that old information does not endlessly circulate
through redundant paths in the network, preventing the effective propagation of the new information. Set by
the Root Bridge, this value will aid in determining that the Switch has spanning tree configuration values
consistent with other devices on the bridged LAN. If the value ages out and a BPDU has still not been
received from the Root Bridge, the Switch will start sending its own BPDU to all other switches for permission
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