F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices Network Management Configuration Guide-6PW100

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When connecting to a point-to-point link, a designated port enters the forwarding state immediately after
the device receives a handshake response from the directly connected device.
78B
MSTP
415BSTP and RSTP limitations
STP does not support rapid state transition of ports. A newly elected port must wait twice the forward
delay time before it transitions to the forwarding state, even if it connects to a point-to-point link or is an
edge port.
Although RSTP supports rapid network convergence, it has the same drawback as STP. All bridges within
a LAN share the same spanning tree, and packets from all VLANs are forwarded along the same
spanning tree, so redundant links cannot be blocked based on VLAN, and load sharing among VLANs
cannot be implemented.
416BMSTP features
Developed based on IEEE 802.1s, MSTP overcomes the limitations of STP and RSTP. In addition to
supporting rapid network convergence, it also provides a better load sharing mechanism for redundant
links by allowing data flows from different VLANs to be forwarded along separate paths.
MSTP provides the following features:
• Divides a switched network into multiple regions, each of which contains multiple spanning trees
that are independent of one another.
• Supports mapping VLANs to spanning tree instances by means of a VLAN-to-instance mapping
table. MSTP can reduce communication overheads and resource usage by mapping multiple
VLANs to one instance.
• Prunes a looped network into a loop-free tree, which avoids proliferation and endless cycling of
packets. In addition, it supports load balancing of VLAN data by providing multiple redundant
paths for data forwarding.
• Compatible with STP and RSTP.
417BMSTP basic concepts
2204HFigure 42 shows a switched network that comprises four MST regions, with each MST region comprising
four MSTP devices.
2205HFigure 43 shows the network topology of MST region 3.