Problem Connections between MSTP and RSTP

[bartosz.wrzosek]

Hello
I have a network at work as shown in the attached diagram.
Region 1 is in the MSTP
Region 2 is in the MSTP
and it is connected by a switch in the RSTP.
The scheme is simplified, of course i real , Region 1 I have 20 switches and Region 2 I have 50 switches.

The main switch for all switches is RSTP, It is the MST0 master in both regions and is the CST master.

Four VLANS are exchanged between the two regions and the RSTP switch. These are Vlan 1 which must be and for simplicity VLAN 10,11,12
Everything is OK during normal work.

Vlan priorities on RSTP switch are set Vlan 1 8192 and Vlans 2-4094 priority 0

In region Region 1 MST0 is set to priority 8192 MST 1 to priority 16384 and R2 MST0 priority 16384 MST1 priority 24576

The problem begins when resetting switches, especially those that connect to RSTP, then I have "no communication" for about 30 seconds.

My question is how should I have priorities on vlans and instances so that STP rebuilds quickly?

And what should I have to have vans passed between the regions and the RSTP

(Only Vlan 1 and Vlan 10,11,12)

Second topic dashed line I marked the connections that I want to make in the future connection of two MSTP regions.
How I should set ports Z1 to Z4 be if all was ok.

[paul driver]

Hello

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@bartosz.wrzosek wrote:

The problem begins when resetting switches, especially those that connect to RSTP, then I have "no communication" for about 30 seconds.

My question is how should I have priorities on vlans and instances so that STP rebuilds quickly?

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What does resetting the switch(s) actually involve?

[bartosz.wrzosek]

I do, for example, the RELOAD command, for example after uploading the new fimware.
Or the second situation is to take the power off the switch for maintenance work

[paul driver]

Hello
A 30 second convergence i would isn’t that long for a reload of a switch however It all depends on what switches you do this to, is it on the boundary switches , Not forgetting you have the rstp switch the root for both mst regions so then your in the realms of negating pvst simulation scenarios

[bartosz.wrzosek]

Hello

"Not forgetting you have the rstp switch the root for both mst regions so then your in the realms of negating pvst simulation scenarios"

And you can develop what that means for me? Maybe some special configuration should still be there. I also tried the configuration that CST is in one of the two regions. Unfortunately it does not work for me. When restarting the main CST switch from the R1 region, communication with the R2 region was lost and the switch RSTP switch took over the CST roles. I could ask you for a sample configuration for my network with CST in one of the regions

BR

[Elliot Dierksen]

At a high level, MST versus PVST only matters on trunks. If it is 4 VLAN's, you could use 4 access ports to interface between the MST and PVST regions. You shouldn't have conflicts then,

I had some customers with a mix of PVST and MST long ago (I always discouraged that), but I did use the following command on a trunk interface to make it play nicer.

interface FastEthernet0/2
 power inline never
 switchport trunk encapsulation dot1q
 switchport mode trunk
 spanning-tree mst pre-standard

That config is from 2006, so take it with a grain of salt.

[bartosz.wrzosek]

Hello

I understand that this configuration for a switch from the MSTP region and what about a switch in RSTP, an additional specific configuration is needed.

And what configuration should be between two regions MSTP  (in my diagram point Z1 to Z4)
I set up port mode trunk and acces vlan 1 and I have P2P dispute on the port in one Region.

BR

[paul driver]

Hello
When you have mst and non mst regions connecting then only vlan 1 of the non-mst switch and mst instance 0 of a mst switch comnpare bpdus also mst boundary switch(s) are then aware they connecting to a non mst region as such they enable pvst simulation on those ports.

In your case you have RSTP and the mst region1 the same pritotiys,

RSTP switch 
Vlan 1 8192
Vlans 2-4094 0

Region 1
MST0 8192
MST 1 16384 

Region2
MST0 16384
MST1 priority 24576

If you wisj the mst 1 region to be the root then something like the below should be applicable:

RSTP switch 
Vlan 1 16384
Vlans 2-4094 20480

Region 1  <--root
MST0 0
MST 1 4098 

Region 2
MST0 8192
MST1 priority 12288

[bartosz.wrzosek]

Hello

I did as you wrote in the second case, i.e. CST switch is in the R1 region
When I turn on the ports between region R1 and RSTP everything is OK (Ports P1, P2, P5, P6)
When I connect the secound port from the R2 region, P3(first) next P7  gets the PVST_INC message and Loop  is created. 

Port P4 and P8 port is not connected.
When I disabled Ports P1 P2 P5 P6.
And I will start to turn on the ports P3 P4 P7 P8 everything is ok (Region 2)
When it turn  on the P1 and P5 port, it gets a message PVST_INC on the P8 port again

Do you have any idea why this is happening?

Switch R1 MST 0 prority 0 MST1 prority 4097 

Switch R2 MST0 pro 0  MST1 pro 12289 (no connected to R1 and RSTP I try ping in vlan 11)

P1 P2 P5 P6 I allowed Vlan 1,10,11,12

P3 P4 P7 P8 I allowed Vlan 1,11,12

Connnected Z1to Z4 does not exist at this moment

Today I have made the MST configuration on all switches again is the same.

BR