I have three switches I'd like to configure in a loop – a Cisco stack (3750s) and two HP 2900 series. Each is connected to the next with a 10 gig backplane of one form or another.
How do I configure the spanning tree on these systems to make this function correctly? From the documents I've looked at it looks like I need to set both sets of hardware to use MST mode but I'm not sure past that point. The trunking, etc is all set up as needed.
HP Switch 1 A4 connected to Cisco 1/0/1.
HP Switch 2 B2 connected to Cisco 2/0/1.
HP Switch 1 A2 connected to HP Switch 2 A1.
HP Switch 1
show spanning-tree
Multiple Spanning Tree (MST) Information
STP Enabled : Yes
Force Version : MSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : 0021f7-126580
Switch Priority : 32768
Max Age : 20
Max Hops : 20
Forward Delay : 15
Topology Change Count : 352,485
Time Since Last Change : 2 secs
CST Root MAC Address : 0018ba-c74268
CST Root Priority : 1
CST Root Path Cost : 200000
CST Root Port : 1
IST Regional Root MAC Address : 0021f7-126580
IST Regional Root Priority : 32768
IST Regional Root Path Cost : 0
IST Remaining Hops : 20
Root Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports :
PVST Protected Ports :
PVST Filtered Ports :
| Prio | Designated Hello
Port Type | Cost rity State | Bridge Time PtP Edge
----- --------- + --------- ---- ---------- + ------------- ---- --- ----
...
A1 | Auto 128 Disabled |
A2 10GbE-CX4 | 2000 128 Forwarding | 0021f7-126580 2 Yes No
A3 10GbE-CX4 | Auto 128 Disabled |
A4 10GbE-SR | 2000 128 Forwarding | 0021f7-126580 2 Yes No
HP Switch 2
show spanning-tree
Multiple Spanning Tree (MST) Information
STP Enabled : Yes
Force Version : MSTP-operation
IST Mapped VLANs : 1-4094
Switch MAC Address : 0024a8-cd6000
Switch Priority : 32768
Max Age : 20
Max Hops : 20
Forward Delay : 15
Topology Change Count : 19,623
Time Since Last Change : 32 secs
CST Root MAC Address : 0018ba-c74268
CST Root Priority : 1
CST Root Path Cost : 202000
CST Root Port : A1
IST Regional Root MAC Address : 0024a8-cd6000
IST Regional Root Priority : 32768
IST Regional Root Path Cost : 0
IST Remaining Hops : 20
Root Guard Ports :
TCN Guard Ports :
BPDU Protected Ports :
BPDU Filtered Ports :
PVST Protected Ports :
PVST Filtered Ports :
| Prio | Designated Hello
Port Type | Cost rity State | Bridge Time PtP Edge
----- --------- + --------- ---- ---------- + ------------- ---- --- ----
...
A1 10GbE-CX4 | 2000 128 Forwarding | 0021f7-126580 2 Yes No
A2 10GbE-CX4 | Auto 128 Disabled |
B1 SFP+SR | 2000 128 Blocking | a44c11-a67c80 2 Yes No
B2 | Auto 128 Disabled |
Cisco Stack 1
show spanning-tree
... (additional VLANs)
VLAN0100
Spanning tree enabled protocol ieee
Root ID Priority 1
Address 0018.bac7.426e
Cost 2
Port 107 (TenGigabitEthernet2/1/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)
Address a44c.11a6.7c80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Te1/1/1 Desg FWD 2 128.53 P2p
Te2/1/1 Root FWD 2 128.107 P2p
Best Answer
The Cisco side isn't configured for MST. Take a look here for specifics, but you need to set the 3750 to use the appropriate mode and assign the various ports in the switch to an instance corresponding to the HP's (likely instance 0, but I don't know their implementation). That should - in broad strokes - get the switches at least speaking the same protocol.
Beyond this, I would highly recommend that you explicitly configure one of the three as the root bridge. This is configured on a per-instance basis - lower switch priority wins. A quick Google search turned up some suggested example configs for interoperability. The document in this link has some appropriate warnings about older IOS revisions, but if you're running something reasonably current it's safe to disregard.