Brocade Mobility Access Point System Reference Guide (Supporting software release 5.5.0.0 and later) - Manual (Page 268)

258 Brocade Mobility Access Point System Reference Guide
53-1003100-01
5
FIGURE 130 Ethernet Ports – Spanning Tree Configuration
Spanning Tree Protocol (STP) (IEEE 802.1D standard) configures a meshed network for robustness
by eliminating loops within the network and calculating and storing alternate paths to provide fault
tolerance.
STP calculation happens when a port comes up. As the port comes up and STP calculation happen,
the port is set to Blocked state. In this state, no traffic can pass through the port. Since STP
calculations take up to a minute to complete, the port is not operational thereby effecting the
network behind the port. Once the STP calculation is complete, the port’s state is changed to
Forwarding and traffic is allowed.
Rapid Spanning Tree Protocol (RSTP) (IEEE 802.1w standard) is a evolution over the standard STP
where the primary aim was to reduce the time taken to respond to topology changes while being
backward compatible with STP. PortFast enables quickly changing the state of a port from Blocked
to Forwarding to enable the port to allow traffic while the STP calculation happens.
Multiple Spanning Tree Protocol (MSTP) provides an extension to RSTP to optimize the usefulness
of VLANs. MSTOP allows for a separate spanning tree for each VLAN group, and blocks all but one
of the possible alternate paths within each spanning tree topology.
If there is just one VLAN in the access point managed network, a single spanning tree works fine.
However, if the network contains more than one VLAN, the network topology defined by single STP
would work, but it is possible to make better use of the alternate paths available by using an
alternate spanning tree for different VLANs or groups of VLANs.