Product and Software: This article applies to Aruba s3500 and all ArubaOS versions.
MST (802.1s) is an enhanced version of the STP protocol. MST is supported in Aruba s3500.
A. STP (802.1d) creates only one instance of STP in the whole network.
Advantages: Much less CPU and memory overhead
Disadvantages: No redundancy, load balancing
B. PVST+ creates a different STP instance for each VLAN. PVST+ achieves load balancing by blocking certain ports for certain VLANs and blocking other ports of other VLANs.
Advantages: High redundancy, load balancing
Disadvantages: High CPU and memory overhead
C. MST maps several instances of VLANs to an instance of STP. MST provides optimum load balancing and lesser CPU and memory usage.
Advantages: High redundancy, load balancing, lower CPU and memory usage
Disadvantages: More configuration
Points to Remember
- MSTP is disabled by default. All ports in VLANs and all interfaces that are in Layer 2 mode are added to MSTP when it is enabled.
- Portfast, loopguard, and rootguard are disabled by default.
- MSTP allows formation of multiple spanning tree regions and each region can run multiple instances. MSTP allows users to map a set of VLANs to a MSTP instance.
- For two switches to be in the same MSTP region, they must share the same name, the same version, and the same VLAN instance mapping.
- When an Aruba s3500 receives RSTP/STP control packets from a neighbor, the neighbor is considered to be in a different region. For the RSTP/STP neighbor, the entire MSTP region appears to be a single bridge.
(Vikas) (config) #mstp
(Vikas) (Global MSTP) #enable
(Vikas) (Global MSTP) #region-name new-MST
forward-delay Forward-delay in seconds [4-30]. Default: 15 seconds
hello-time Hello-time in seconds [1-10]. Default: 2 seconds
instance MST instance [0-64]
max-age Maximum age in seconds [6-40]. Default: 20 seconds
max-hops Maximum hops [6-40]. Default: 20 seconds
no Delete Command
region-name MSTP region name in bytes [1-32]
revision Revision [0-65535]. Default: 0