Comware

Hello!

I have a couple of  S5120-28C-PWR-EI  switches here.
They are connected to each other with 2 Ethernet cables.

Im trying to establish an evaluation setup for MSTP here.

Everything is working so far. Except that port cost is not respected in any way.
The same port is always FORWARDING, no matter if i put very high port cost on this one, and very low port cost on the other one.

 ----[Port19(GigabitEthernet1/0/19)][FORWARDING]----
 Port Role           :Master Port
 Port Priority       :128
 Port Cost(Legacy)   :Config=201 / Active=201
 Desg. Bridge/Port   :0.3ce5-a637-ebca / 128.19
 Num of Vlans Mapped :2
 Port Times          :RemHops 20

 ----[Port20(GigabitEthernet1/0/20)][DISCARDING]----
 Port Role           :Alternate Port
 Port Priority       :128
 Port Cost(Legacy)   :Config=8 / Active=8
 Desg. Bridge/Port   :0.3ce5-a637-ebca / 128.20
 Num of Vlans Mapped :2
 Port Times          :RemHops 20

[SW-VIE-IT29-GigabitEthernet1/0/20]dis this
#
interface GigabitEthernet1/0/20
 description "STPTEST1"
 port link-type trunk
 undo port trunk permit vlan 1
 port trunk permit vlan 77 to 78
 port trunk pvid vlan 79
 poe enable
 stp instance 1 cost 8
#

How is that possible?

Regards,
ND

Hi 

It is observed that when you connect two 5120 switches using two cable the port with least port number is preferred than that of the port priority .

In your case the port 19 would always be the root port . You can try connecting another cable on 21 which has higher port number and shut the 19 port and observe . As per my theory the 20th port would be the root port and would be in forwarding state .

Please raise a case with HPE TAC to verify if it is a firmware issue .

So, are you trying to say "cost" and "priority" parameters are useless, because those H3C switches are taking the port number with the lowest value as those with lowest cost?

Wow, that would be a horrific bug.
We don't have any lower ports available on those coreswitches, they are all filled up already.

We just had a troubleshooting session with all kind of combinations of priority, cost and stp standard settings.
That one port is always discarding. Except if you pull the network cable from the other one. Then it changes to FORWARDING.

There seems to be really no way to accomplish this.

Hi

I noticed the change of cost affects the STP also the priority on the root switch affects the election .

Last time I was checking on the non root switch . You can also try modifying the STP parameters on the root switch .