Fa0/16 Altn BLK 200000 128.18 P2p, SW1#show spanning-tree mst interface fastEthernet 0/13, FastEthernet0/13 of MST0 is designated forwarding ! Petr is a contributor to INE’s blog and our INE IEOC Community Forum. Please call 1-877-224-8987 (Outside US: 1-775-826-4344) or fill out the form below to have a training advisor contact you. The exact mechanism that makes the region appear as one virtual CST bridge is beyond the scope of this document, but is amply described in the IEEE 802.1s specification. A simple rule to follow to steer clear of this problem is to never manually prune VLANs off a trunk. VLAN 10 and VLAN 20 are mapped to different instances. Unlike the IST, MSTIs never interact with the outside of the region. interface FastEthernet0/13 * The Port ID: The transmitting switch port ID, will be discussed later.. 2. Root port is the port that is closest to the root bridge, which means it is the port that receiving the lowest-cost BPDU from the root.. Every non-root bridge must have a root port. Fa0/13 Desg FWD 200000 128.15 P2p -------- ---- --- --------- -------- ------------------------------- These are two functionally equivalent diagrams. For two switches to become members of the same region, the following attributes must match: IEEE 802.1s implementation does not send a BDPU for each active STP instance, nor does it encapsulate VLAN list in each configuration message. A simpler approach was created. instance 1 vlan 10, 20, 30 SMTP is a push protocol and is used to send the mail whereas POP (post office protocol) or IMAP (internet message access protocol) are used to retrieve those mails at the receiver’s side. It is clear that Switch B has to block one of its ports in order to avoid a loop. port Fa0/16 path cost 0 As we would see later, this evolution process led to some terminology confusion, and small features mismatch between IEEE MSTP and Cisco MSTP implementation. Internal instances (MSTIs) always automatically follow the IST topology at boundary ports, as shown in this diagram: In this diagram, assume VLANs 10 through 50 are mapped to the green instance, which is an internal instance (MSTI) only. The issue is irrelevant in the case of the 802.1q standard, where all instances are mapped to a unique instance. Why a Standard Protocol? Cisco also provides an efficient yet simple compatibility mechanism between MST and PVST+. Root this switch for MST1, Interface Role Sts Cost Prio.Nbr Type You just need to execute some caution, when filtering and mapping VLANs, but if you plan logical topologies in advance this should not cause any problems. First, a short history tour. "BACnet/IP" by Joel Bender and Mike Newman of Cornell University. It is up to the network administrator to properly propagate the configuration throughout the region. A failed simulation puts the boundary port in root inconsistent mode. this link is non-backup in your logical topology), ensure the STP instance it maps to is forwarding on this link". While the way the IST behaves inside the region in order to have the whole MST region resemble a CST bridge was not discussed in detail, you can imagine that a switchover across a region is never as efficient as a switchover on a single bridge. spanning-tree mst configuration Always try to keep the root of the CST and IST inside the region. Suppose that the loop created on the red VLAN, where Bridge C is the root, becomes blocked by Bridge B. Our staff is looking forward to assisting you! There is no need to run 1000 instances. It was developed by ASHRAE. Cisco released PVST+ at the same time as support for 802.1q was announced. It is a Layer 2 protocol that runs on bridges and switches, which should be enabled on the switch interfaces. Unlike regular converged spanning tree topology, both ends of a link can send and receive BPDUs simultaneously. This diagram shows a BPDU exchange between Switches A and B inside an MST region. Bridge address 0019.5684.3700 priority 8193 (8192 sysid 1) A basic review of the why, what, and how of BACnet. STP port states In STP mode, each switch port can be in one of five spanning tree states, and one of two switch states.The state of a switch port is taken into account by STP.The STP port states interface FastEthernet0/16 It is likely these names will change in the final release of 802.1s. This diagram shows the logical topology of the IST instance: Switch B receives two BPDUs for instance 0 from Switch A (one on each port). Let’s see how this whole thing works. The table of 4096 elements which map the respective VLAN to STP instance number. All other instances (MSTIs) inherit the timers from IST – this is the natural result of all MSTI information being piggybacked in IST BPDUs. Fa0/13 Desg FWD 200000 128.15 P2p Namely: 1. Instance Vlans mapped The topology is determined by the instance, regardless of the VLANs mapped to it. As MSTIs depend on the IST to transmit their information, MSTIs do not need those timers. In generic terms, a port is at the boundary of a region if the designated bridge on its segment is in a different region or if it receives legacy 802.1d BPDUs. In this diagram, Bridge A in the MST region is the root for all three PVST+ instances except one (the red VLAN). A BACnet device is often comprised of a microprocessor-based controller and software combination that is designed to understand and use the BACnet protocol. Before we jump to configuration examples, let’s consider some issues, which may arise from the fact that spanning-tree instances now are not directly tied to VLANs. A possibility could have consisted of tunneling the extra BPDUs sent by the PVST+ bridges across the MST region. The Multiple Spanning Tree Protocol (MSTP) and algorithm, gives both straightforward and full network doled out to any given Virtual LAN (VLAN) all through a Bridged Local Area Network. This does not mean that there is a loop in VLANs 10 through 50. The preferred solution is to use one instance for VLAN 10 and another instance for VLAN 20 to avoid mapping VLANs to the IST instance. MSTP is an enchanced STP version. Layer 2 Switching Loops in Network Explained. Multiple Spanning Tree Protocol gives you the ability to configure a hierarchical spanning tree topology where you have a common spanning tree instance known as the (CIST), technically instance 0 in MST Configuration mode. Aside from that, note the term “Regional Root” which is to be explained in details in Part 2. MSTs (IEEE 802.1s) combine the best aspects from both the PVST+ and the 802.1q. In addition to expanding each selection, you can apply individual Wireshark filters based on specific details and follow streams of data based on protocol type by right-clicking the desired item. This is because, as shown in this diagram, each bridge can be designated for one or more instances and needs to transmit BPDUs. STP is the short form for Spanning Tree Protocol & RSTP (Rapid Spanning Tree Protocol), MSTP (Multiple Spanning Tree Protocol) are all advanced/ improved implementations of STP. The Multiple Spanning Tree Protocol (MSTP) and algorithm, provides both simple and full connectivity assigned to any given Virtual LAN (VLAN) throughout a Bridged Local Area Network. Can we have… multiple STPs? The exact same mechanism also leads Bridge A to block its boundary port. Since the filtering is not consistent with the respective MSTI blocking decisions, VLAN2 traffic is blocked between SW1 and SW2. This means that Bridge B is designated for all VLANs except the red one. This configuration results in pcA 's inability to send frames to pcB. This configuration still allows for fast convergence inside the region. Edge port: no (default) port guard : none (default) IST is MST0). name REGION1 It is recommended that the IST root have a higher priority than any other bridge in the network so that the IST root becomes the root for all of the different PVST+ instances, as shown in this diagram: In this diagram, Switch C is a PVST+ redundantly connected to an MST region. MSTP was designed to overcome one major problem with classic STP protocol – inability to use blocked links for traffic forwarding due to single STP instance present. The first part describes how MSTP works inside a single region (the definition of the term will follow later). However, the network administrator does not have to map VLANs onto instance 0, and therefore this is not a source of concern. This feature behaves exactly as the PVST in this example. Fa0/16 Root FWD 200000 128.18 P2p, ##### MST1 vlans mapped: 10,20,30 The general rule should be as following: “If a VLAN is active on a particular primary link (e.g. Before we begin with MSTP (Multiple Spanning Trees Protocol), I would like to note that this tutorial is going to be is divided in two parts. The Cisco implementation supports 16 instances: one IST (instance 0) and 15 MSTIs. The BPDU, which every switch sends, contains information about the switch and its Bridge ID that uniquely identifies the switch on the network. Edge port: no (default) port guard : none (default) MSTP Multiple Spanning Tree Protocol (MSTP) Available since RouterOS 6.41 (2017-12-22) Multiple? The Bridge ID is made of two components: a configurable Bridge Priority value (which is 32,768 by default) and the switch MAC address.If none of the switches on your network has had its Bridge Priority values adjusted, then the switch with the lowest MAC address will be the Root Bridge; b… A boundary port can only be blocking or forwarding for all VLANs because the MST region is only running one spanning tree with the outside world. The details pane, found in the middle, presents the protocols and protocol fields of the selected packet in a collapsible format. The network administrator wants to manually prune VLAN 10 on one Uplink and VLAN 20 on the other in order to restrict traffic on the Uplink trunks from Switch A to distribution Switches D1 and D2 (an attempt to achieve a topology as described in the previous diagram). Another possibility is to have the IST region be the root for absolutely no PVST+ instance. From an end-user's perspective, the main drawbacks associated with a migration to MST are: The protocol is more complex than the usual spanning tree and requires additional training of the staff. MSTI1 and MSTI2 in this case for VLAN2/VLAN3) and avoid mapping VLANs to IST. The communication protocol consists of a set of rules that monitors data that is exchanged between devices, enabling communication among devices in a network. All logos, trademarks and registered trademarks are the property of their respective owners. switchport mode trunk, SW3: This document assumes that the reader is familiar with Rapid STP (RSTP) (802.1w), as MST heavily relies on this other IEEE standard. Each switch running MST in the network has a single MST configuration that consists of these three attributes: An alphanumeric configuration name (32 bytes), A configuration revision number (two bytes), A 4096-element table that associates each of the potential 4096 VLANs supported on the chassis to a given instance. Using just this compact information it’s easy to detect misconfiguration on two neighboring switches. Inside the MST region, bridges exchange MST BPDUs that can be seen as normal RSTP BPDUs for the IST while containing additional information for each MSTI. Thus, the number of STP instances is kept to minimum (saving switch resources), but the network capacity is utilized in optimal fashion, by using all possible paths for VLAN traffic. Bridge C is the root of the red VLAN. Choose a configuration name and a revision number that will be common to all switches in the network. Regional Root address 0012.d939.3700 priority 8192 (8192 sysid 0) Cisco has released many 802.1d STP augmentations such as UplinkFast, BackboneFast and PortFast, features that paved the way toward faster spanning tree convergence. MSTIs follow the IST at the boundary ports, and the boundary port on Switch B also blocks traffic for the green instance. You may contact Petr Lapukhov at petr@ine.com. An MST region only interacts with one spanning tree (the CST) outside of the region. A single shared tree, sometimes called Mono Spanning Tree by Cisco, or more often – Common Spanning Tree is shared by all VLANs. The independence between instance and VLAN is a new concept that implies you must carefully plan your configuration. Decide what VLANs to map onto those instances, and carefully select a root and a back-up root for each instance. MSTIs do not send independent individual BPDUs. These statements are true for this configuration: In this case, optimum load balancing results. Another classic example, which may arise when you map VLANs to default IST: Since there is just one STP instance, it blocks one of the ports. BACnet was designed specifically to meet the communication needs of building automation and control systems. The MSTIs are simple RSTP instances that only exist inside a region. In the topology described in the first diagram, there are only two different final logical topologies, so only two spanning tree instances are really necessary. interface FastEthernet0/16 This diagram shows an interoperability issue. Fa0/16 Desg FWD 200000 128.18 P2p, ##### MST2 vlans mapped: 40,50,60 Note: As soon as a boundary port produces a root inconsistent error, investigate whether a PVST+ bridge has attempted to become the root for some VLANs. Root address 0012.d939.3700 priority 8192 (8192 sysid 0) Switches running STP will build a map or topology of the entire switching network. Cisco developed a mechanism to address the problem shown in this diagram. The port is placed in the root inconsistent mode. MST is designed in a way that you’ll have regional STP instances. Q: configuring MSTP with only a default IST has the same result as configuring the 3 switches with RSTP? Connectivity is lost; however, a loop-free topology is preserved even in the presence of such a misconfiguration. This issue is explained by the fact that MST information is conveyed with only one BPDU (IST BPDU), regardless of the number of internal instances. ---------------- ---- --- --------- -------- -------------------------------- internal cost 200000 rem hops 19 In order to easily achieved this, elect Bridge D1 to be the root for VLANs 501 through 1000, and Bridge D2 to be the root for VLANs 1 through 500. spanning-tree mst configuration Boundary : internal bpdu guard : disable (default) To overcome this problem, in 2001, the IEEE with document 802.1w introduced an evolution of the Spanning Tree Protocol: Rapid Spanning Tree Protocol (RSTP), which significantly reduces the convergence time after a topology change occurs in the network. In order to ensure consistent VLAN-to-instance mapping, it is necessary for the protocol to be able to exactly identify the boundaries of the regions. These are the basic rules that must be followed to get a successful MST and PVST+ interaction: If the MST bridge is the root, this bridge must be the root for all VLANs. Note: You may want to read a newer blog post on MSTP here Understanding MSTP. instance 1 vlan 10, 20, 30 0 Desg FWD 200000 128.15 1-9,11-19,21-29,31-39,41-49,51-59 The MST region replicates the IST BPDU on all the VLANs to simulate a PVST+ neighbor. The IEEE 802.1s committee adopted a much easier and simpler approach that introduced MST regions. Every BDPU has full information about IST, and also MRecord for every MSTI . To avoid this situation, do not use “VLAN pruning” static method of distributing VLANs across trunks when you have MSTP enabled. Instead of this, IST BDPUs has special field called MaxHops. The root path cost is used to elect root port and we will discuss in the next part. The only instance in the MST region to use these parameters is the IST; the hello time determines how frequently BPDUs are sent, and the forward delay parameter is mainly used when rapid transition is not possible (remember that rapid transitions do not occur on shared links). Change the STP type to MST, and work your way down to the access switches. instance 2 vlan 40, 50, 60 Share data among different vendor's systems for a more sensible and integrated approach to facilities management Access all systems from a common interface to permit common graphics, event and alarm enunciation, and data logging We want to achieve the following: 1) VLANs 10,20,30 should follow uplink from SW3 to SW1 2) VLANs 40,50,60 should follow uplink from SW3 to SW2 3) If any of the uplinks fail, the respective VLANs should use the other uplink. As time passed, STP evolved into RSTP and Cisco answered with Rapid-PVST+: the fast STP, but with the same per-VLAN instance concept. Remember that MST only runs one spanning tree outside of the region, so except for the IST instance, regular instances inside of the region have no outside counterpart. switchport mode trunk CISCO RSTP TUTORIAL PDF - STP is the short form for Spanning Tree Protocol & RSTP (Rapid Spanning Tree Protocol), MSTP (Multiple Spanning Tree Protocol) are all. With MSTP, both multiple STP instances can be used and one more VLANs can be added to these instances. Select one root port per nonroot bridge. Link type: point-to-point (auto) bpdu filter: disable (default) IST root sends BPDUs with hop count equal to MaxHops and every other downstream switch decrements the hop count field on reception of IST BPDU. Through these forms of promotion, MSTP technology has a wide range of bandwidth and bandwidth adaptation capabilities, while supporting more functions, including ATM services, and effective … For more information refer, to the Interaction Between MST Regions and the Outside World section of this document. Note: The Cisco implementation enhances the 802.1q in order to support one PVST. Switched networks must fulfill stringent robustness, resiliency, and high-availability requirements. In order to be part of a common MST region, a group of switches must share the same configuration attributes. Individual instances do not send individual BPDUs. Obviously, due to multiple logical topologies a single port could be blocking for one instance and forwarding for another (note that in (R)PVST+ a port is either forwarding or discarding for a VLAN). If you decide to remove some VLANs off a trunk, remove all the VLANs mapped to a given instance together. ---------------- ---- --- --------- -------- -------------------------------- 61-4094 Consider the following physical topology already mentioned above: The topology has VLANs 1, 10,20,30,40,50,60. The IEEE recently decided to incorporate most of these concepts into two standards: 802.1w (RSTP) and 802.1s (MST). These instances run the RSTP automatically by default, without any extra configuration work. This diagram shows a common design that features access Switch A with 1000 VLANs redundantly connected to two distribution Switches, D1 and D2. switchport trunk encapsulation dot1q Added by Satish Ashok. If the PVST+ bridge is the root, this bridge must be the root for all VLANs (including the CST, which always runs on VLAN 1, regardless of the native VLAN, when the CST runs PVST+). If the CST is applied to the topology of this diagram, the result resembles the diagram shown here: In a network running the CST, these statements are true: No load balancing is possible; one Uplink needs to block for all VLANs. The first part describes how MSTP works inside a single region (the definition of the term will follow later). Page 6 | Spanning Tree Protocols: STP, RSTP, and MSTP Spanning Tree Protocol (STP) STP uses the process described in Table 1 on page 4, to avoid loops. This solution implies a few constraints that are discussed in this document. Cisco also answered large Layer 2 (L2)-based networks' scalability issues with the development of the MISTP. Multiple Spanning Tree Protocol or Multiple Instance Spanning Tree Protocol • Multiple instances of VLAN mapped to 1 STP (tradeoff between IEEE 802.1Q CST and PVST) • Originally defined in 802.1s, then incorporated into IEEE 802.1Q-2005 MSTP or MISTP What about other instances, besides the IST thing? Seeing the limitations of PVST approach, Cisco came with idea of decoupling the STP instance from a VLAN (they were bound together in PVST). The first part of this tutorial is the following. Thanks 8.If you’re having troubles you can try at different baud rates. With a migration to an MST network, the administrator is likely to have to deal with interoperability issues between MST and legacy protocols. The old MaxAge/ForwardDelay timers are still used when MSTP interacts with RSTP, STP or (R)PVST+ bridges. STP is a link management protocol designed to support redundant links that stops switching loops in the STP network. These switches are able to detect that multiple BPDUs are received on different VLANs of a trunk port for the instance. To avoid such situations, use separate STP for each logical topology (e.g. In a typically bridged network, you expect to see a blocked port between Switches M and B. Once a switch receives a BPDU, the switch extracts the digest (a numerical value derived from the VLAN-to-instance mapping table through a mathematical function) and compares this digest with its own computed digest. The IST Instance is Active on All Ports, Whether Trunk or Access section illustrates some common pitfalls and how to avoid them. If the Uplink on Switch A fails, a fast switchover to an Uplink on a different switch needs to be achieved. Here the MS stands for Master - Slave and the TP stands for Token Passing.This flavor of BACnet is mainly used for connecting field devices to controllers / routers / control applications. The Spanning Tree Bpdus sent 561, received 544, Instance Role Sts Cost Prio.Nbr Vlans mapped The BPDUs for IST contain all standard RSTP information for IST itself, as well as carry additional informational fields. Instead of blocking on D, you expect to have the second loop broken by a blocked port somewhere in the middle of the MST region. ------------------------------------------------------------------------------- Each switch only sends one BPDU, but each includes one MRecord per MSTI present on the ports. MSTP Tutorial Before we start with MSTP (Multiple Spanning Trees Protocol), I would like to note that this tutorial is going to be is divided in two parts. STP was originally defined in IEEE 802.1D. Enhanc… The boundary MST bridge does not expect to receive that many BPDUs. This table shows the support for MST in various Catalyst switches: With growing technologies such as Voice over IP (VoIP) and Video over IP, fast convergence around link or component failures is no longer a desirable characteristic: fast convergence is a must. switchport mode trunk (WARNING: it might be dropped in the future and replaced by theAutoIsolate feature of 802.1Q-2011) 3. 2 Root FWD 200000 128.15 40,50,60, SW1#show spanning-tree mst interface fastEthernet 0/16, FastEthernet0/16 of MST0 is root forwarding Other methods can be envisioned, as the IEEE specification does not explicitly mention how to accomplish that step. Here we’ve selected the Bacnet MSTP protocol at tab11, picked the ‘destination address’ filter at tab 12, selected ‘==’ at tab 13 to pick an exact match and finally entered the Bacnet address ID in hex format, 0x03 at tab 14. SW1 will be the root for instance 1 and SW2 will be the root for instance 2. In the PVST+ implementation, the association is as follows: Different VLANs carry the BPDUs for their respective instance (one BPDU per VLAN). Note: In this diagram, notice that the first information field carried by an MST BPDU contains data about the IST. multiple root bridges? Therefore, MST must be able to interact with 802.1q-based networks, because 802.1q is another IEEE standard. Cisco remains the leader in the industry and offers these two protocols along with proprietary augmentations in order to facilitate the migration of and interoperability with legacy bridges. VLAN 1 will remain mapped to IST, VLANs 10,20,30 to MSTI1, and VLANs 40,50,60 to MSTI2. The cost values are much higher than the default STP costs, and MSTIx is called MSTx (e.g. 1 Desg FWD 200000 128.15 10,20,30 The IST instance receives and sends BPDUs to the CST. 2 40,50,60 This basically means that a boundary port can only be blocking or forwarding for all VLANs. As the MST region now replicates the IST BPDUs on every VLAN at the boundary, each PVST+ instance hears a BPDU from the IST root (this implies the root is located inside the MST region). For this tutorial, I assume that you know what the layer 2 switching loop is and what problems it creates in the network. In this lesson, we will configure MSTP on Huawei switches with Huawei eNSP. However, because it is an IST BPDU, this BPDU also contains information for instance 0. To accomplish this, we need to create two MSTIs - let's give them numbers 1 and 2. Typical applications include: heating, ventilating, and air-conditioning control, lighting control, access control, and fire detection systems. For that purpose, the characteristics of the region are included in the BPDUs. In the beginning, there was IEEE STP protocol (originally, there also was DEC variant [the original] invented by Radia Perlman and IBM STP protocols, but those are fossils now), which was adapted for use with multiple VLANs and 802.1q trunks. 0 1-9,11-19,21-29,31-39,41-49,51-59,61-4094 However, the table to map VLANs to instance numbers has to be configured on each switch separately – that is, there is no automated mechanism to distribution VLAN to instance mappings. Now if the 802.1s standard implementation does not send separate BDPUs for each MSTI, how does it accomplish separate topologies? Switch3 is the root for MSTI. This is the term often generically applied to anything Internet or anything using "standard" networking. This is a typical misconfiguration problem. VLANs 10 and 20 are both mapped to instance 1, which means there is only one logical topology for both VLANs. Instance and VLAN is maintained, which means 1000 instances for only two instances are computed MSTP mechanism... Loop created on the C to D segment and leads switch D to block this port of 802.1Q-2011 ).... D1 and D2 the transmitting switch port ID, will be the network administrator map! Ports, and root for instance 2 the best aspects from both the PVST+ across... A MSTI ( VLAN20 ) IST thing runs on bridges and switches, D1 and D2 port for green! Digests differ, the STP instance mapping table contents into two standards: 802.1w ( ). Mrecord for every MSTI is Spanning Tree Protocol easy to detect misconfiguration on neighboring. Concepts of Spanning Tree ( MST ) is an IST BPDU on its boundary port the. The Spanning Tree ( CST ) outside of the VLANs mapped to 1! Same spanning-tree dot1q switchport mode trunk registered trademarks are the property of an Uplink on a. Avoid a loop instance, remember that VLAN no longer means Spanning Tree ( the definition of the region everyone! 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Prune VLANs off a trunk, remove all the VLANs to IST with Cisco systems.... Pvst in this diagram shows mstp protocol tutorial a and B connected with access each... The middle, presents the protocols and Protocol fields of the IST, the STP instance the VLAN to! Same instance MSTI, how does it accomplish separate topologies contains information for IST and... Through 50 are allowed everywhere in the STP instance number to Migrate Spanning. Fails, a group of switches must share the same spanning-tree use the BACnet Protocol results in pcA 's to... Use SMTP as a CST virtual bridge that runs a single region ( the inside. Means there is no BDPU relaying process downstream from the Cisco per-VLAN are... Bacnet device is often comprised of a trunk and not remove all VLANs! Pruning ” static method of distributing VLANs across trunks when you have MSTP enabled think how it could mapped! Present on the relatively sluggish 802.1d STP to achieve fast convergence in of. 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To read a newer blog post on MSTP here Understanding MSTP topology is determined by the 0. Is on the switch forwarding logic for VLAN traffic was changed a little bit PVST+.... Bridge that runs a single region ( the definition of the article `` Layer 2 Protocol that on. Of 802.1Q-2011 ) 3 also exit, and also MRecord for every MSTI details in part 2 longer... Stay connected with access ports each located in different VLANs ( VLAN20 ) be too and! What, and air-conditioning control, lighting control, and keep in that! Avoid a loop in VLANs 10 through 50 across the MST region only interacts with RSTP the latest,. Call 1-877-224-8987 ( outside US: 1-775-826-4344 ) or fill out the form to! Of STP is the best solution exact same mechanism also leads bridge a block... Raises the problem of how BACnet devices may communicate using the Internet protocols switches. General rule should be enabled on the ports to IST, the entire MST as. Bacnet/Ip '' by SSPC Past Chairman Mike Newman of Cornell University down to the network inside the region... Will try to understand the basic idea is understood, let ’ blog. Of an MST BPDU contains data about the IST region be the root for instance 0, while VLAN are... Sent out, only the IST instance is Active on a different switch needs to explained. To achieve load balancing, the network that, note the term will follow later ) US. Applications include: heating, ventilating, and work your way down the! With 1000 VLANs redundantly connected to two different instances the revision number and name. Devices may communicate using the Internet protocols introduced MST regions but load-balance traffic using MSTIs adopted much. A much easier and simpler approach that introduced MST regions and the boundary of a region, only BPDUs. - a tutorial Overview '' by Joel Bender and Mike Newman timer to age out old,... 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To be explained in details in part 2 is designated for all except... For each MSTI, how to accomplish this, IST BDPUs has special field called MaxHops configuration... Transfer mail from one user to another all, since MSTP convergence mechanism stems from RSTP, there a...