CCNP Switch (300 - 115) version 2.0: MSTP introduction

now in this video we'll talk about multiple spanning tree introduction to multiple spanning tree and before we get into the multiple spanning tree in the previous video we have seen something about four-wheelin spanning tree in case of per wheel and spanning tree what we can do is we can map a specific VLANs like VLAN 10 maybe 1 to 20 all the VLANs for all these VLANs we can have a separate route which a as a root bridge and we can configure for VLAN 21 to 40 the remaining 20 VLANs we can make this as a root bridge now in this way we can do something called load sharing but the major drawback with the per wheel and spanning tree is even though we can do some load shredding but still it is going to run one STP instance for each and every VLAN so which means in this example if I'm running for TV lands in that case the every switch is going to run a separate instance for each and every VLAN so 40 STP instances now to overcome this we can run something called multiple spanning tree initially started by Cisco within Cisco terminology recalled as multiple instance of spanning tree protocol originally standardized in eight node 2.1 s now the main difference here is now in case of multiple spanning tree we can define a set of VLANs to be mapped now once you enable MSTP default it's going to create a common spanning tree but again now here what I can do is I can define some set of VLANs let's say I can say that we learn one two VLAN 20 I'm assuming I got some 40 VLANs and I'm saying that I can I can group this VLANs into one common spanning tree one STP instance rather than having a separate entity P instance for each and every be lab let's let's take an example in my diagram here now assume that I got a VLAN 1 to VLAN 20 and then I got a VLAN 21 to VLAN 40 here now total there are 40 VLANs so which means by default it's going to run pbht which means there are 40 STP instances going to run if I go with a PV st now instead we can we can change the configuration to MST wait we can run one common spanning tree for 20 VLANs and we can we can run a separate spanning tree instance for the remaining 20 VLANs that's what we call as instance to instant more instance 2 and all the remaining VLANs or whatever the future VLANs which we are going to create they by default goes into B for instance called MST is 0 now in the switch every switch we just ran a we are just running default 3 instances in fact if you if you assume that there are only 40 VLANs we are just running only 2 instance of STP rather than running a force 40 separate instances of STV so in this way we are reducing the overhead on the switches by by having a very less number of STP instances running and at the same time we can have something called load sharing option where we can configure that in case of instance 1 we can define that a is primary and P secondary or just just we can define that a switch should be the primary root bridge for for instance 1 which means it will apply for all the 20b lands and I can define that B is a primary switch for all the remaining VLANs now in this way I can do some I can have something called separate forwarding paths for a and supplied forwarding path for B again so that's what here you can see I can have for instance one this will be the forwarding for instance 1 and this will be the blocking port for instance 1 and for instance 2 this will be the forwarding when it says 2 and this root will be the blocking State now in this way I am going to provide some load sharing that is one of the advantage we get the same thing what you can hu by using volumes by and also we are minimizing the cpu resources minimizing the CPD resources by by running a common instance of spanning tree for a set of reruns so that's how it's going to work now let us see some more some more on MSTP here now when when we start confidential of MSTP we define something called instance name let's take an example I got some six features here and I want these four switches to run a common spanning tree that is a multiple spanning tree for a group of VLANs and in order for this to work you must you must match these three configurations so you need to define some name for the region region name we called as and that region name let's say I'm giving CCIE now all the four switches has to match this region name that's what we call as instance name the region name and then they must match the revision number as well when we define something or revision number two by revision number and then the instance two real and mappings like let's say on instance one I'm defining the all the VLANs from VLAN 1 to 20 and on the instance two I am defining some VLANs from 21 to 40 so this mapping has to match in all the switches now then they are going to run some common spanning tree common instance of a spanning tree for this group of freelance now the conversation wise it's little bit straightforward configuration where the first command we are going to enable now this command is going to enable MSTP on all the switches now we just need to say spanning tree mode MST now once I give spanning tree mode MST what we are going to do is it's going to enable the default is PVS tree but if you want you can run a rapid spanning tree now default is pbht it's going to change to MSTP and then we can get into the configuration of spanning tree MST configuration we can define some revision memory name so just ensure that this this configuration matches on all the switches and then we create some instances like instance one instance two and the default instance will be MST zero now whenever you create any instance by default all the VLANs once you enable this command by default all the VLANs will be in default instance of MST zero but we can create some instances multiple instances here instance one instance two and we can define what set of VLANs should be in the instance one and what set of VLANs should be on the instance two and then we can change the rules and I can say that for instance one this is primary so that it is forward it is using all the ports in the forwarding and then probably blocking this sport and for instance two I'm going to say that for instance ooh this is my primary switch now by having some supplied route bridges for different instances we can provide some load sharing okay so the instance must have the same MST name and the revision number that is something you need to ensure that they have the same MST name M the revision number if it's not going to match they will be concerned as in normal different instances and it's going to run a common spanning tree between them now it comes to common MSTP interoperability now we got some intra region intra region kind of things now once you run a common spanning tree configurations within this within the multiple switches now they will be covered as normal MST multiple spanning tree intra region within the same region so in between different regions now you can have multiple MSTP instances instances created in a different regions we call them as internal inter region where you have some different region names and the details between the regions are not known here and in between them it's going to run something called common spanning tree now MSTP is backward compatible with with the legacy CST it's something no more used and also with P vs T plus and in general it's going to behave just like inter region MST configuration where you have some set of switches which is conferred with MSTP and then there are some switches which are not confer with MSTP it's going to treat them as outside the region or inter region MST configurations

Channel: Sikandar Shaik

Views: 48,763

Keywords: stp, stp stock, CCNP

Id: r2gnfsJeQo4

Length: 9min 9sec (549 seconds)

Published: Mon Jun 08 2015