LevelOne GEL-5261, User Manual

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Chapter 7
| Spanning Tree Algorithm
Configuring Global Settings for STA
Figure 103: Configuring Port Loopback Detection
Configuring Global Settings for STA
Use the Spanning Tree > STA (Configure Global - Configure) page to configure
global settings for the spanning tree that apply to the entire switch.
Command Usage
◆ Spanning Tree Protocol 3
This option uses RSTP set to STP forced compatibility mode. It uses RSTP for the
internal state machine, but sends only 802.1D BPDUs. This creates one
spanning tree instance for the entire network. If multiple VLANs are
implemented on a network, the path between specific VLAN members may be
inadvertently disabled to prevent network loops, thus isolating group
members. When operating multiple VLANs, we recommend selecting the MSTP
option.
◆ Rapid Spanning Tree Protocol
3
RSTP supports connections to either STP or RSTP nodes by monitoring the
incoming protocol messages and dynamically adjusting the type of protocol
messages the RSTP node transmits, as described below:
■
STP Mode – If the switch receives an 802.1D BPDU (i.e., STP BPDU) after a
port’s migration delay timer expires, the switch assumes it is connected to
an 802.1D bridge and starts using only 802.1D BPDUs.
■
RSTP Mode – If RSTP is using 802.1D BPDUs on a port and receives an RSTP
BPDU after the migration delay expires, RSTP restarts the migration delay
timer and begins using RSTP BPDUs on that port.
◆ Multiple Spanning Tree Protocol
MSTP generates a unique spanning tree for each instance. This provides
multiple pathways across the network, thereby balancing the traffic load,
3. STP and RSTP BPDUs are transmitted as untagged frames, and will cross any VLAN
boundaries.