Spanning tree problem 2848 with cisco 6500

[Lutz Muehlig]

Hello,

I have 2 coreswitches (cat6500) connected with a trunk. Then I connect a HP 2848 via 1Gb to each Cat6500. Spanning Tree ist working fine, one Port of the 2848 is in blocking state, the other in forwarding. STP is configured on all switches as MST.
One Cat6500 is rootbridge and over this connection the traffic flows.
Now I want, that the traffic goes over the port of the 2848, who was before in blocking state. I changed the cost of this port (down to 100) but nothing changes. The port ist still in blocking mode.

I have tested this setup with a Cisco 3750 in case of the HP2848 and then it works...

What is wrong?
Regards Lutz

[Shadow13]

The cost in MST in hp is different as shown below
10 MB = 2,000,000
100 Mb = 200,000
1 Gb = 20,000
10 Gb = 2,000

so change the cost depending on these costs, try to raise the cost of the forwarding state and return the cost of the blocked port to it's normal cost and see if it works.

And as you mentioned you are using MST, did you configure 1 instance only for MST or more than 1 ?? if you did configure more than 1 instance then the port can be blocked for 1 instance and forwarding for the other isntance, plz post more information about this and if you can post the output of
#show span

from all of the switches it will help alot.


Regards,
Islam Hassan

[Lutz Muehlig]

I set the blocking port to auto cost (20000) and raised the forwarding port to 900000 but no changes.
We use now a 2910 for the test but it is the same problem like with 2848.
Here is the config:

ProCurve 2910al-48G Switch# sh spanning-tree

Multiple Spanning Tree (MST) Information

STP Enabled : Yes
Force Version : MSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : 0024a8-d66240
Switch Priority : 32768
Max Age : 8
Max Hops : 20
Forward Delay : 5

Topology Change Count : 1
Time Since Last Change : 6 mins

CST Root MAC Address : 00141b-2fbec0
CST Root Priority : 24576
CST Root Path Cost : 0
CST Root Port : 48

IST Regional Root MAC Address : 00141b-2fbec0
IST Regional Root Priority : 24576
IST Regional Root Path Cost : 20000
IST Remaining Hops : 19

Root Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports : 1-41,43-46
PVST Protected Ports :
PVST Filtered Ports :

| Prio | Designated Hello
Port Type | Cost rity State | Bridge Time PtP Edge
----- --------- + --------- ----- ---------- + ------------- ----- --- ----
1 100/1000T | Auto 128 Disabled |
2 100/1000T | Auto 128 Disabled |
3 100/1000T | Auto 128 Disabled |
4 100/1000T | Auto 128 Disabled |
5 100/1000T | Auto 128 Disabled |
6 100/1000T | Auto 128 Disabled |
7 100/1000T | Auto 128 Disabled |
8 100/1000T | Auto 128 Disabled |
9 100/1000T | Auto 128 Disabled |
10 100/1000T | Auto 128 Disabled |
11 100/1000T | Auto 128 Disabled |
12 100/1000T | Auto 128 Disabled |
13 100/1000T | Auto 128 Disabled |
14 100/1000T | Auto 128 Disabled |
15 100/1000T | Auto 128 Disabled |
16 100/1000T | Auto 128 Disabled |
17 100/1000T | Auto 128 Disabled |
18 100/1000T | Auto 128 Disabled |
19 100/1000T | Auto 128 Disabled |
20 100/1000T | Auto 128 Disabled |
21 100/1000T | Auto 128 Disabled |
22 100/1000T | Auto 128 Disabled |
23 100/1000T | Auto 128 Disabled |
24 100/1000T | Auto 128 Disabled |
25 100/1000T | Auto 128 Disabled |
26 100/1000T | Auto 128 Disabled |
27 100/1000T | Auto 128 Disabled |
28 100/1000T | Auto 128 Disabled |
29 100/1000T | Auto 128 Disabled |
30 100/1000T | Auto 128 Disabled |
31 100/1000T | Auto 128 Disabled |
32 100/1000T | Auto 128 Disabled |
33 100/1000T | Auto 128 Disabled |
34 100/1000T | Auto 128 Disabled |
35 100/1000T | Auto 128 Disabled |
36 100/1000T | Auto 128 Disabled |
37 100/1000T | Auto 128 Disabled |
38 100/1000T | Auto 128 Disabled |
39 100/1000T | Auto 128 Disabled |
40 100/1000T | Auto 128 Disabled |
41 100/1000T | Auto 128 Disabled |
42 100/1000T | Auto 128 Disabled |
43 100/1000T | Auto 128 Disabled |
44 100/1000T | Auto 128 Disabled |
45 100/1000T | Auto 128 Disabled |
46 100/1000T | Auto 128 Disabled |
47 1000SX | 20000 128 Blocking | 00115d-ee2800 2 Yes No
48 1000SX | 90000000 128 Forwarding | 00141b-2fbec0 2 Yes No

ProCurve 2910al-48G Switch# sh run

Running configuration:

; J9147A Configuration Editor; Created on release #W.14.30

hostname "ProCurve 2910al-48G Switch"
no cdp run
module 1 type J9147A
vlan 1
name "DEFAULT_VLAN"
untagged 1-41,46,48
tagged 47
no untagged 42-45
no ip address
exit
vlan 2
name "VLAN2"
tagged 47-48
no ip address
exit
vlan 4
name "VLAN4"
untagged 42-44
tagged 47-48
no ip address
exit
no lldp run
spanning-tree
spanning-tree 1 admin-edge-port
spanning-tree 1 bpdu-filter
spanning-tree 2 admin-edge-port
spanning-tree 2 bpdu-filter
spanning-tree 3 admin-edge-port
spanning-tree 3 bpdu-filter
spanning-tree 4 admin-edge-port
spanning-tree 4 bpdu-filter
spanning-tree 5 admin-edge-port
spanning-tree 5 bpdu-filter
spanning-tree 6 admin-edge-port
spanning-tree 6 bpdu-filter
spanning-tree 7 admin-edge-port
spanning-tree 7 bpdu-filter
spanning-tree 8 admin-edge-port
spanning-tree 8 bpdu-filter
spanning-tree 9 admin-edge-port
spanning-tree 9 bpdu-filter
spanning-tree 10 admin-edge-port
spanning-tree 10 bpdu-filter
spanning-tree 11 admin-edge-port
spanning-tree 11 bpdu-filter
spanning-tree 12 admin-edge-port
spanning-tree 12 bpdu-filter
spanning-tree 13 admin-edge-port
spanning-tree 13 bpdu-filter
spanning-tree 14 admin-edge-port
spanning-tree 14 bpdu-filter
spanning-tree 15 admin-edge-port
spanning-tree 15 bpdu-filter
spanning-tree 16 admin-edge-port
spanning-tree 16 bpdu-filter
spanning-tree 17 admin-edge-port
spanning-tree 17 bpdu-filter
spanning-tree 18 admin-edge-port
spanning-tree 18 bpdu-filter
spanning-tree 19 admin-edge-port
spanning-tree 19 bpdu-filter
spanning-tree 20 admin-edge-port
spanning-tree 20 bpdu-filter
spanning-tree 21 admin-edge-port
spanning-tree 21 bpdu-filter
spanning-tree 22 admin-edge-port
spanning-tree 22 bpdu-filter
spanning-tree 23 admin-edge-port
spanning-tree 23 bpdu-filter
spanning-tree 24 admin-edge-port
spanning-tree 24 bpdu-filter
spanning-tree 25 admin-edge-port
spanning-tree 25 bpdu-filter
spanning-tree 26 admin-edge-port
spanning-tree 26 bpdu-filter
spanning-tree 27 admin-edge-port
spanning-tree 27 bpdu-filter
spanning-tree 28 admin-edge-port
spanning-tree 28 bpdu-filter
spanning-tree 29 admin-edge-port
spanning-tree 29 bpdu-filter
spanning-tree 30 admin-edge-port
spanning-tree 30 bpdu-filter
spanning-tree 31 admin-edge-port
spanning-tree 31 bpdu-filter
spanning-tree 32 admin-edge-port
spanning-tree 32 bpdu-filter
spanning-tree 33 admin-edge-port
spanning-tree 33 bpdu-filter
spanning-tree 34 admin-edge-port
spanning-tree 34 bpdu-filter
spanning-tree 35 admin-edge-port
spanning-tree 35 bpdu-filter
spanning-tree 36 admin-edge-port
spanning-tree 36 bpdu-filter
spanning-tree 37 admin-edge-port
spanning-tree 37 bpdu-filter
spanning-tree 38 admin-edge-port
spanning-tree 38 bpdu-filter
spanning-tree 39 admin-edge-port
spanning-tree 39 bpdu-filter
spanning-tree 40 admin-edge-port
spanning-tree 40 bpdu-filter
spanning-tree 41 admin-edge-port
spanning-tree 41 bpdu-filter
spanning-tree 42 admin-edge-port
spanning-tree 43 admin-edge-port
spanning-tree 43 bpdu-filter
spanning-tree 44 admin-edge-port
spanning-tree 44 bpdu-filter
spanning-tree 45 admin-edge-port
spanning-tree 45 bpdu-filter
spanning-tree 46 admin-edge-port
spanning-tree 46 bpdu-filter
spanning-tree 48 path-cost 90000000
spanning-tree config-name "CORE"
spanning-tree config-revision 1
spanning-tree forward-delay 5 maximum-age 8
management-vlan 2

[Lutz Muehlig]

and here are the cat6500:

core1#sh spanning-tree

MST0
Spanning tree enabled protocol mstp
Root ID Priority 24576
Address 0014.1b2f.bec0
This bridge is the root
Hello Time 2 sec Max Age 8 sec Forward Delay 5 sec

Bridge ID Priority 24576 (priority 24576 sys-id-ext 0)
Address 0014.1b2f.bec0
Hello Time 2 sec Max Age 8 sec Forward Delay 5 sec

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/2 Desg FWD 20000 128.2 P2p
Gi1/40 Desg FWD 20000 128.40 P2p
Gi5/2 Desg FWD 20000 128.514 P2p
Po1 Desg FWD 6660 96.1665 P2p


core2#sh spanning-tree

MST0
Spanning tree enabled protocol mstp
Root ID Priority 24576
Address 0014.1b2f.bec0
Cost 0
Port 1665 (Port-channel1)
Hello Time 2 sec Max Age 8 sec Forward Delay 5 sec

Bridge ID Priority 28672 (priority 28672 sys-id-ext 0)
Address 0011.5dee.2800
Hello Time 2 sec Max Age 8 sec Forward Delay 5 sec

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/2 Desg FWD 20000 128.2 P2p
Gi5/2 Desg FWD 200000 128.514 P2p
Po1 Root FWD 6660 96.1665 P2p

[Richard Brodie_1 · Accepted solution]

You appear to have put all the switches in one MST region. Within the region, you need to change the instance path costs.

span instance ist path-cost

[Lutz Muehlig]

Thanks Richard,

that was the solution.

Regards
Lutz