Guidelines And Limitations For Configuring Mst - Cisco Nexus 7000 Series Configuration Manual

Configuring MST Using Cisco NX-OS

Guidelines and Limitations for Configuring MST

When you change the VLAN-to-MSTI mapping, the system reconverges MST.
Note
MST has the following configuration guidelines and limitations:
• You must enable MST; Rapid PVST+ is the default spanning tree mode.
• You can assign a VLAN to only one MST instance at a time.
• You cannot map VLANs 3968 to 4047 or 4094 to an MST instance. These VLANs are reserved for
• You can have up to 65 MST instances on one device.
• The maximum number of VLANs and ports is 75,000.
• By default, all VLANs are mapped to MSTI 0 or the IST.
• You can load balance only within the MST region.
• Ensure that trunks carry all of the VLANs that are mapped to an MSTI or exclude all those VLANs that
• Always leave STP enabled.
• Do not change timers because you can adversely affect your network stability.
• Keep user traffic off the management VLAN; keep the management VLAN separate from user data.
• Choose the distribution and core layers as the location of the primary and secondary root switches.
• Port channeling—The port channel bundle is considered as a single port. The port cost is the aggregation
• When you map a VLAN to an MSTI, the system automatically removes that VLAN from its previous
• You can map any number of VLANs to an MSTI.
• All MST boundary ports must be forwarding for load balancing between Rapid PVST+ and an MST
• Do not partition the network into a large number of regions. However, if this situation is unavoidable,
The software supports full nondisruptive upgrades for MST. See the Cisco Nexus 7000 Series NX-OS
Note
High Availability and Redundancy Guide for complete information about nondisruptive upgrades.
internal use by the device.
are mapped to an MSTI.
of all the configured port costs assigned to that channel.
MSTI.
cloud or between a PVST+ and an MST cloud. The CIST regional root of the MST cloud must be the
root of the CST. If the MST cloud consists of multiple MST regions, one of the MST regions must
contain the CST root and all of the other MST regions must have a better path to the root contained
within the MST cloud than a path through the Rapid PVST+ or PVST+ cloud.
we recommend that you partition the switched LAN into smaller LANs interconnected by non-Layer 2
devices.
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x

Guidelines and Limitations for Configuring MST

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