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5-5
Multiple Instance Spanning-Tree Operation
Overview
Note on Path Cost RSTP and MSTP implements a greater range of path costs and new default
path cost values to account for higher network speeds. These values are
different than the values defined by 802.1D STP as shown below.
Because the maximum value for the path cost allowed by 802.1D STP is 65535,
devices running that version of spanning tree cannot be configured to match
the values defined by MSTP, at least for 10 Mbps and 100 Mbps ports. In LANs
where there is a mix of devices running 802.1D STP, RSTP, and/or MSTP, you
should reconfigure the devices so the path costs match for ports with the same
network speeds.
Port Type 802.1D STP Path Cost RSTP and MSTP Path Cost
10 Mbps 100 2 000 000
100 Mbps 10 200 000
1 Gbps 5 20 000