Introduction To Mstp; Why Mstp - H3C S5810 Series Operation Manual

Introduction to MSTP

Why MSTP

1) Weaknesses of STP and RSTP
STP does not support rapid state transition of ports. A newly elected root port or designated port must
wait twice the forward delay time before transiting to the forwarding state, even if it is a port on a
point-to-point link or an edge port, which directly connects to a user terminal rather than to another
device or a shared LAN segment.
Although RSTP supports rapid network convergence, it has the same drawback as STP does: All
bridges within a LAN share the same spanning tree, so redundant links cannot be blocked based on
VLAN, and the packets of all VLANs are forwarded along the same spanning tree.
2) Features of MSTP
The Multiple Spanning Tree Protocol (MSTP) overcomes the shortcomings of STP and RSTP. In
addition to the support for rapid network convergence, it also allows data flows of different VLANs to be
forwarded along separate paths, thus providing a better load sharing mechanism for redundant links.
For description about VLANs, refer to VLAN Configuration in the Access Volume.
MSTP features the following:
MSTP supports mapping VLANs to MST instances (MSTIs) by means of a VLAN-to-MSTI mapping
table. MSTP can reduce communication overheads and resource usage by mapping multiple
VLANs to one MSTI.
MSTP divides a switched network into multiple regions, each containing multiple spanning trees
that are independent of one another.
MSTP prunes a loop network into a loop-free tree, thus avoiding proliferation and endless cycling of
packets in a loop network. In addition, it provides multiple redundant paths for data forwarding, thus
supporting load balancing of VLAN data.
MSTP is compatible with STP and RSTP.
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