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Spanning-tree port type p2p bound


hi all,

I'm having trouble running MST on 4 switches.

The MST should be configured for the same region, 2 instances.

Instance 1 with Vlans 10, 20, 50
Instance 2 with Vlans 30, 40, 80

Core1 should be root bridge for instance 1 and core2 should be root bridge for instance 2.
On the two Access switches i get porttype "P2p Bound (RSTP)" which im not sure how to fix.

Also, on Access 2, it doesnt even seem to be running instance 1, even though it is configured. Below picture is an overview of the output of

show span mst

from all 4 switches. As you can see in lower right corner, Access2 only has Instance 2.



output of

sh run | sec mst

from all 4 switches:


I hope someone can explain to me why Access2 is not running instance 2, what port type P2p Bound (RSTP) means, why it's there and how to get it right. Thanks in advance



1 Accepted Solution

Accepted Solutions

show vlan 

do you see vlan for mst 1 ?

View solution in original post

10 Replies 10

since the MST can compatible with RSTP, 
f one SW run MST and other run RSTP then the MST will mark the port that connect to SW run RSTP as p2p bound (RSTP).

check the spanning tree mode config in all SW


Here is output of

show span summary

which shows all switches are running MST. What else can i do?

@MHM Cisco Worldas you can also see, it looks like something has gone wrong with the MST configuration, since i have 3 switches being root bridge for instance 2 and 2 switches being root bridge for instance 1. But i really have no idea what i did wrong.

what you do wrong is 
SW have two MST 
SW have three MST 
why you config it like this 
the number of MST must be same in all SW, and the VLAN mapping to MST instance must be same in all SW. 

Hello again,

Of course, but it seems to me that i have made the exact same configuration on all of the switches. Please help me find my error, i will provide all necessary information. First output of 

show current

in MST configuration mode and output of

sh run | sec mst


Here output of

show spanning-tree mst:


I found a command for restarting the protocol, the command

clear spanning-tree detected-protocol

which i ran on all 4 switches. It seems to have cleared something up:
1. In instance 1, there is now only one root bridge and 2 other are participating in the instance. Access2 is still missing.
2. In instance 2, there is also only one root bridge and all 3 other switches are participating in the instance.
3. Now there isn't any "P2p Bound" port types.

As you can clearly see in the first picture, Access2 is configured with both instances, but it wont show in the second picture. Any help would be highly appreciated.



Access2 the missing MST, 
are you see vlan of this MST appear in MST 0??
I think you missing config instance in Acc2.

I just reconfigured, as seen in this picture:


and here is the result:


Do you have any other ideas?

show vlan 

do you see vlan for mst 1 ?

No. Thank you. You are a legend!

and you are so so welcome 

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