Odd stp issue on foundrys

Question

I have 2 foundry devices running 802.1w which are both connected to an access switch which also runs 802.1w.

The 2 foundry's are connected to each as well.

I have the vlan configured on each of the devices to participate in spanning tree however when I add the tag/trunk ports to the vlan, the end devices configured on the access switch lose connectivity. As soon as I remove the tagged ports from the vlan either on switchA or switchB, the connectivity gets restored.

It's not making much sense to me why it doesn't work when the tagged ports are added to the vlans.

SwitchA vlan config:

vlan 16 by port                                       
 tagged ethe 2/1 ethe 8/21 to 8/22                                
 router-interface ve 16                                           
 spanning-tree 802-1w                                             
 spanning-tree 802-1w priority 4096

SwitchB vlan config:

vlan 16 by port
 tagged ethe 2/2 ethe 5/1 to 5/2
 router-interface ve 16
 spanning-tree 802-1w
 spanning-tree 802-1w priority 8192

This is the output from SwitchA:

Port IEEE 802.1W Parameters:

       <--- Config Params --><-------------- Current state -----------------> 
Port   Pri PortPath P2P Edge Role       State       Designa-  Designated       
Num        Cost     Mac Port                        ted cost  bridge           
2/1    128 200000   F   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/21   128 20000    T   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/22   128 20000    T   F    DESIGNATED FORWARDING  0         10000012f21e880f

This is the output from SwitchB:

      <--- Config Params -->|<------------- Current state ------------------->
Port  Pri PortPath  P2P Edge Role       State       Designa-  Designated       
Num       Cost      Mac Port                        ted cost  bridge           
2/2   128 200000    F   F    ALTERNATE       DISCARDING  19        f010001380fa0480 
5/1   128 20000    T   F    DESIGNATED FORWARDING  0         f010001380fa0480 
5/2   128 20000    T   F    DESIGNATED FORWARDING  0         f010001380fa0480

Now with the config like this, connectivity is lost. When I remove either the 5/1-5/2 or the 8/21-8/22 from either switch, connectivity gets restored.

The access switch down below has the following:

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/18              Desg FWD 19        128.18   P2p 
Fa0/46              Desg FWD 19        128.46   P2p 
Fa0/47              Root FWD 19        128.47   P2p 
Fa0/48              Desg FWD 19        128.48   P2p

Ports 47+48 are the uplinks ports going to the foundry's and 18+46 are going to end user equipment.

This doesn't make sense to me why this happens.

Anyone have an explanation or a fix for this?

Thanks

More info

From SwitchA:

--- VLAN 16 [ STP Instance owned by VLAN 16 ] ----------------------------

Bridge IEEE 802.1W Parameters:

Bridge           Bridge Bridge Bridge Force    tx   
Identifier       MaxAge Hello  FwdDly Version  Hold 
hex              sec    sec    sec             cnt  
10000012f21e880f 20     2      15     Default  3    

RootBridge       RootPath  DesignatedBri-   Root  Max Fwd Hel 
Identifier       Cost      dge Identifier   Port  Age Dly lo  
hex                        hex                    sec sec sec 
10000012f21e880f 0         10000012f21e880f Root  20  15  2   

Port IEEE 802.1W Parameters:

       <--- Config Params --><-------------- Current state -----------------> 
Port   Pri PortPath P2P Edge Role       State       Designa-  Designated       
Num        Cost     Mac Port                        ted cost  bridge           
2/1    128 200000   F   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/21   128 20000    F   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/22   128 20000    F   F    DESIGNATED FORWARDING  0         10000012f21e880f

From SwitchB:

--- VLAN 16 [ STP Instance owned by VLAN 16 ] ----------------------------

Bridge IEEE 802.1W Parameters:

Bridge           Bridge Bridge Bridge Force    tx   
Identifier       MaxAge Hello  FwdDly Version  Hold 
hex              sec    sec    sec             cnt  
2000000cdba0d20f 20     2      15     Default  3    

RootBridge       RootPath  DesignatedBri-   Root  Max Fwd Hel 
Identifier       Cost      dge Identifier   Port  Age Dly lo  
hex                        hex                    sec sec sec 
10000012f21e880f 200019    f010001380fa0480 2/2   20  15  2   

          <--- Config Params -->|<------------- Current state ------------------->
    Port  Pri PortPath  P2P Edge Role       State       Designa-  Designated       
    Num       Cost      Mac Port                        ted cost  bridge           
    2/2   128 200000    F   F    ALTERNATE       DISCARDING  19        f010001380fa0480 
    5/1   128 20000    T   F    DESIGNATED FORWARDING  0         f010001380fa0480 
    5/2   128 20000    T   F    DESIGNATED FORWARDING  0         f010001380fa0480

REDID CONFIG and NOW GET THE FOLLOWING

SwitchA:

--- VLAN 16 [ STP Instance owned by VLAN 16 ] ----------------------------

Bridge IEEE 802.1W Parameters:

Bridge           Bridge Bridge Bridge Force    tx   
Identifier       MaxAge Hello  FwdDly Version  Hold 
hex              sec    sec    sec             cnt  
10000012f21e880f 20     2      15     Default  3    

RootBridge       RootPath  DesignatedBri-   Root  Max Fwd Hel 
Identifier       Cost      dge Identifier   Port  Age Dly lo  
hex                        hex                    sec sec sec 
10000012f21e880f 0         10000012f21e880f Root  20  15  2   

Port IEEE 802.1W Parameters:

       <--- Config Params --><-------------- Current state -----------------> 
Port   Pri PortPath P2P Edge Role       State       Designa-  Designated       
Num        Cost     Mac Port                        ted cost  bridge           
2/1    0   200000   F   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/21   128 20000    F   F    DESIGNATED FORWARDING  0         10000012f21e880f 
8/22   128 20000    F   F    DESIGNATED FORWARDING  0         10000012f21e880f

SwitchB:

--- VLAN 16 [ STP Instance owned by VLAN 16 ] ----------------------------

Bridge IEEE 802.1W Parameters:

Bridge           Bridge Bridge Bridge Force    tx   
Identifier       MaxAge Hello  FwdDly Version  Hold 
hex              sec    sec    sec             cnt  
2000000cdba0d20f 20     2      15     Default  3    

RootBridge       RootPath  DesignatedBri-   Root  Max Fwd Hel 
Identifier       Cost      dge Identifier   Port  Age Dly lo  
hex                        hex                    sec sec sec 
10000012f21e880f 20000     10000012f21e880f 5/1   20  15  2   

Port IEEE 802.1W Parameters:

      <--- Config Params -->|<------------- Current state ------------------->
Port  Pri PortPath  P2P Edge Role       State       Designa-  Designated       
Num       Cost      Mac Port                        ted cost  bridge           
2/2   128 200000    F   F    ALTERNATE  DISCARDING  19        f010001380fa0480 
5/1   128 20000     F   F    ROOT       FORWARDING  0         10000012f21e880f 
5/2   128 20000     F   F    ROOT       FORWARDING  0         10000012f21e880f

There is something wrong with your spanning tree configuration. Neither Foundry switch has a port in the "Root" role, so it would appear that they both believe they are the root bridge. Could you add more details on the spanning tree configuration? — YLearn, Mar 26 '14 at 01:46
Hi Ylearn, I updated my post with some more info. Let me know if you need anything else. Thx — Network Samurai, Mar 26 '14 at 01:56
Still no connectivity even when it shows the root port as 5/1 on SwitchB. — Network Samurai, Mar 26 '14 at 02:14
Can you add a diagram? Since both 5/1 and 5/2 are showing a role as root, they are both connected to switch A. But I can't figure out how you have it wired. Which ports are connected between the Foundrys, and which are the links to the access switch? — Ron Trunk, Mar 26 '14 at 02:37
5/1 & 5/2 are connected to 8/21 & 8/22 for the foundrys. They are running LACP. Port 47 goes to SwitchA and port 48 goes to SwitchB from the access switch. — Network Samurai, Mar 26 '14 at 02:47
What's the access switch? How is it configured? Are you trying to have a per-vlan stp? — Ricky, Mar 26 '14 at 18:06
After all your changes, can you also add the STP config from the access switch as well as the output from "show spanning-tree summary" and "show spanning-tree vlan 16"? Remember, Cisco devices will do PVST by default, and 802.1w basically operates like CST. — YLearn, Mar 26 '14 at 23:17
@NetworkNinja, was this problem ever solved? If so could you either accept Ricky's answer or post your own with the resolution? — Mike Pennington, Jun 25 '14 at 02:08
Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer. — Ron Maupin, Jan 05 '21 at 02:06

Ricky · Answer 1 · 2014-03-26T19:30:57.827

2

5/1 & 5/2 are connected to 8/21 & 8/22 for the foundrys. They are running LACP. Port 47 goes to SwitchA and port 48 goes to SwitchB from the access switch.

Then what you are seeing is exactly what you should see... STP killing the loop. Switch A & B are connected via their LACP trunk. And then an access switch is connected to BOTH Switch A and B. One of those two links will be (MUST BE) blocked.

There may be a disconnect between the access and main switches, as the access switch is in the FWD state on all ports. I've never seen a stack do that.

edited Mar 26 '14 at 19:30

answered Mar 26 '14 at 03:10

Ricky

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With 802.1w, doesn't discarding replace blocking from regular spanning tree 802.1d? There is no blocking role in 802.1w. Can you pls clarify? – Network Samurai Mar 26 '14 at 09:06
On the mgmt vlan of the access switch, I have the same config as vlan 16 yet there is no connectivity loss when having both sides of the lacp trunk added to the vlan. Any idea why that vlan works but this one doesn't then? Thanks – Network Samurai Mar 26 '14 at 09:14

Odd stp issue on foundrys

1 Answers1