ISSUE: SG350XG-24F stack problems; link flapping

IFM · ‎06-17-2019

Hi,

we use two SG350XG-24F as a Stack as core switches and 3 SG350XG-48T as access switches.

The stack members are connected on fiber ports 23 and 24.

Each access switch is connected via DAC to each stack member. No LAG there.

We only created a LAG on port 3 of each fiber switch to our firewall. Is LAG even needed in stack mode if we dont want to use aggregation but simple failover?

Right now we are facing network outages and link flapping on several ports.

Any ideas?

Firmware is 2.4.5.71.

2147483556	2018-Nov-09 22:44:12	Warning	%STP-W-PORTSTATUS: te2/0/7: STP status Blocking   
2147483557	2018-Nov-09 22:43:32	Warning	%STP-W-PORTSTATUS: te2/0/7: STP status Forwarding   
2147483558	2018-Nov-09 22:42:30	Warning	%STP-W-PORTSTATUS: te2/0/12: STP status Forwarding
2147483559	2018-Nov-09 22:42:25	Warning	%STP-W-PORTSTATUS: te2/0/5: STP status Forwarding   
2147483560	2018-Nov-09 22:42:24	Warning	%STP-W-PORTSTATUS: te2/0/10: STP status Forwarding   
2147483561	2018-Nov-09 22:42:24	Warning	%STP-W-PORTSTATUS: te2/0/6: STP status Forwarding   
2147483562	2018-Nov-09 22:42:23	Notice	%STCK SYSL-N-UNITMSG: UNIT ID 2,Msg:%SYSLOG-N-LOGGING: Logging started.    
2147483563	2018-Nov-09 22:42:00	Informational	%LINK-I-Up:  te2/0/12   
2147483564	2018-Nov-09 22:41:59	Warning	%LINK-W-Down:  te2/0/12   
2147483565	2018-Nov-09 22:41:59	Warning	%STP-W-PORTSTATUS: te2/0/4: STP status Forwarding   
2147483566	2018-Nov-09 22:41:59	Warning	%STP-W-PORTSTATUS: te2/0/3: STP status Forwarding   
2147483567	2018-Nov-09 22:41:59	Warning	%STP-W-PORTSTATUS: te2/0/11: STP status Forwarding   
2147483568	2018-Nov-09 22:41:58	Warning	%STP-W-PORTSTATUS: te2/0/8: STP status Forwarding   
2147483569	2018-Nov-09 22:41:58	Informational	%TRUNK-I-PORTADDED: Port te2/0/1 added to Po1   
2147483570	2018-Nov-09 22:41:55	Informational	%LINK-I-Up:  te2/0/12   
2147483571	2018-Nov-09 22:41:55	Informational	%LINK-I-Up:  te2/0/5   
2147483572	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/4   
2147483573	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/3   
2147483574	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/11   
2147483575	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/10   
2147483576	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/8   
2147483577	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/7   
2147483578	2018-Nov-09 22:41:54	Informational	%LINK-I-Up:  te2/0/6   
2147483579	2018-Nov-09 22:41:53	Informational	%LINK-I-Up:  te2/0/1

Kind regards,

Seb Rupik · ‎06-17-2019

Hi there,

If you are getting a steady stream of these STP messages then it clearly is a re-convergence issue you are experiencing.

Given that running LAG provides additional bandwidth and doesn't suffer from failover delay like a pair of STP enabled uplinks, it strike me as the obvious solution to implement.

cheers,

Seb.

IFM · ‎06-17-2019

Hi Seb,

thanks for your input. As the stack only supports 8 LAGs and I already use 1 for my uplink, I cant connect every downstream switch via LAG.
Do you have any other tips to make this work? IMHO this structure is not to uncommon.

We simply want to have automatic failover on core side.

Kind regards,

Seb Rupik · ‎06-17-2019

Is your access layer connected to the core by a single link?

Perhaps I am mis-understanding your topology, can you provide a diagram?

cheers,

Seb.

IFM · ‎06-17-2019

Hi,

I attached a png of our structure. In the png there are 3 access layers switch connected to two core layer switches with one cable to each stack member of core layer. From there we use a LAG to connect to the firewall.

Kind regards,

Hendrik

Seb Rupik · ‎06-17-2019

Do you send the switch logs to an external server?

Can you filter what logs you have for the occurrence of the string:

%STCK

eg: sh logg | inc %STCK

...and share the output here.

It looks like the second switch in the stack is reloading.

cheers,

Seb.

IFM · ‎06-17-2019

09-Nov-2018 22:42:23 :%STCK SYSL-N-UNITMSG: UNIT ID 2,Msg:%SYSLOG-N-LOGGING: Logging started.
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%MLDP-I-CONNECT: Connection to Unit 1 is established.
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%MLDP-I-SLAVE: Switching to the Slave Mode.
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-ACTIVE: Stack port te24 is active in stack LAG 1
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-UP: Stack port te24 operational status is UP
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-ACTIVE: Stack port te23 is active in stack LAG 1
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-UP: Stack port te23 operational status is UP
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%PNPAGENT-I-AGENTREADY: PnP is ready
09-Nov-2018 22:41:40 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%INIT-I-InitCompleted: Initialization task is completed

This are the log entries I got. I can generate some new logs but I will have to connect the second switch in the stack first and this will take some time.

Kind regards,

Seb Rupik · ‎06-17-2019

OK now I'm a little bit confused. From your diagram I thought that the two 350X switches were stacked together. Are you saying they are separate, or is one of them kept powered off??

The logs you have supplied show a stack being established. Is this a constant occurrence during 'normal' operation or have you just established the stack connections?

cheers,

Seb.

IFM · ‎06-17-2019

Hi,

sorry! The two 350x are stacked. I just kept stack member 02 offline/disconnected from power as this solved the network problems.
I can plug it in during maintenance and collect the needed logs.

Kind regards,
Hendrik

Seb Rupik · ‎06-18-2019

If you could power up and connect both core stack members that would be great. Once both are online share the output of:

sh spanning detail

...also run the same command on one of the access layer switches too and share the output.

Can you also configure root-guard on the all switchports and ensure the core switch is the STP root bridge for all locally routed VLANS. This should stem the tide of re-convergence and err-disable the switchports instead. Checking the logs with this feature enabled will give us a better indication of where the fault lies.

cheers,

Seb.

IFM · ‎06-25-2019

Hi Seb,

root guard has to be enabled on all ports on both core switches, correct?

Kind regards,
Hendrik

Seb Rupik · ‎06-30-2019

Hi Hendrik,

Yes, providing 'both core switches' are actually one logical unit, ie stacked together.

If they are logically separate, then adding root-guard on the links will cause additional problems with your topology.

cheers,

Seb.

IFM · ‎12-22-2019

Hi Seb,

christmas time is fixing time ;-)

I finally powered on the second core. One thing I found was that loopback-guard was disabled on the stack and the bridge priority was 32768 like on the other access switches.

Here is the output:

sw-fra-c#sh spanning-tree detail


Spanning tree enabled mode RSTP
Default port cost method:  long
Loopback guard:   Enabled



  Root ID    Priority    4096
             Address     70:c9:c6:f9:5c:27
             This switch is the root
             Hello Time  2 sec  Max Age 20 sec  Forward Delay 15 sec

  Number of topology changes 1031 last change occurred 00:03:54 ago
  Times:  hold 1, topology change 35, notification 2
          hello 2, max age 20, forward delay 15

Interfaces

te1/0/1 is a member of Po1


Port te1/0/2 enabled
State: disabled                                Role: disabled
Port id: 128.2                                 Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.2                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/3 enabled
State: forwarding                              Role: designated
Port id: 128.3                                 Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.3                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 72
BPDU: sent 9138517, received 238

Port te1/0/4 enabled
State: forwarding                              Role: designated
Port id: 128.4                                 Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.4                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 52
BPDU: sent 9138516, received 216

Port te1/0/5 enabled
State: forwarding                              Role: designated
Port id: 128.5                                 Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.5                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 80
BPDU: sent 9138526, received 203

Port te1/0/6 enabled
State: forwarding                              Role: designated
Port id: 128.6                                 Port cost: 20000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.6                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 9138475, received 365

Port te1/0/7 enabled
State: forwarding                              Role: designated
Port id: 128.7                                 Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.7                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 45
BPDU: sent 2241, received 9138078

Port te1/0/8 enabled
State: forwarding                              Role: designated
Port id: 128.8                                 Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.8                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 78
BPDU: sent 9138524, received 200

Port te1/0/9 enabled
State: forwarding                              Role: designated
Port id: 128.9                                 Port cost: 20000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.9                      Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 9058970, received 227

Port te1/0/10 enabled
State: forwarding                              Role: designated
Port id: 128.10                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.10                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 45
BPDU: sent 9138524, received 216

Port te1/0/11 enabled
State: forwarding                              Role: designated
Port id: 128.11                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.11                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 79
BPDU: sent 9138528, received 197

Port te1/0/12 enabled
State: forwarding                              Role: designated
Port id: 128.12                                Port cost: 20000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.12                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 9059401, received 815

Port te1/0/13 enabled
State: disabled                                Role: disabled
Port id: 128.13                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.13                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/14 enabled
State: disabled                                Role: disabled
Port id: 128.14                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.14                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/15 enabled
State: disabled                                Role: disabled
Port id: 128.15                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.15                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/16 enabled
State: disabled                                Role: disabled
Port id: 128.16                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.16                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/17 enabled
State: disabled                                Role: disabled
Port id: 128.17                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.17                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/18 enabled
State: disabled                                Role: disabled
Port id: 128.18                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.18                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/19 enabled
State: disabled                                Role: disabled
Port id: 128.19                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.19                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/20 enabled
State: disabled                                Role: disabled
Port id: 128.20                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.20                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/21 enabled
State: disabled                                Role: disabled
Port id: 128.21                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.21                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te1/0/22 enabled
State: disabled                                Role: disabled
Port id: 128.22                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.22                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

te2/0/1 is a member of Po1


Port te2/0/2 enabled
State: disabled                                Role: disabled
Port id: 128.54                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.54                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/3 enabled
State: forwarding                              Role: designated
Port id: 128.55                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: Yes (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.55                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 242639, received 181

Port te2/0/4 enabled
State: forwarding                              Role: designated
Port id: 128.56                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: Yes (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.56                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 242630, received 216

Port te2/0/5 enabled
State: forwarding                              Role: designated
Port id: 128.57                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.57                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 242621, received 177

Port te2/0/6 enabled
State: forwarding                              Role: designated
Port id: 128.58                                Port cost: 20000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.58                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 164533, received 168

Port te2/0/7 enabled
State: forwarding                              Role: designated
Port id: 128.59                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.59                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 59713, received 11669

Port te2/0/8 enabled
State: forwarding                              Role: designated
Port id: 128.60                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: Yes (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.60                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 166590, received 179

Port te2/0/9 enabled
State: disabled                                Role: disabled
Port id: 128.61                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.61                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/10 enabled
State: forwarding                              Role: designated
Port id: 128.62                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: Yes (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.62                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 166846, received 179

Port te2/0/11 enabled
State: forwarding                              Role: designated
Port id: 128.63                                Port cost: 2000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.63                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 164355, received 154

Port te2/0/12 enabled
State: forwarding                              Role: designated
Port id: 128.64                                Port cost: 20000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.64                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 164004, received 328

Port te2/0/13 enabled
State: disabled                                Role: disabled
Port id: 128.65                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.65                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/14 enabled
State: disabled                                Role: disabled
Port id: 128.66                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.66                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/15 enabled
State: disabled                                Role: disabled
Port id: 128.67                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.67                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/16 enabled
State: disabled                                Role: disabled
Port id: 128.68                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.68                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/17 enabled
State: disabled                                Role: disabled
Port id: 128.69                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.69                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/18 enabled
State: disabled                                Role: disabled
Port id: 128.70                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.70                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/19 enabled
State: disabled                                Role: disabled
Port id: 128.71                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.71                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/20 enabled
State: disabled                                Role: disabled
Port id: 128.72                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.72                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/21 enabled
State: disabled                                Role: disabled
Port id: 128.73                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.73                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port te2/0/22 enabled
State: disabled                                Role: disabled
Port id: 128.74                                Port cost: 2000000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.74                     Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po1 enabled
State: forwarding                              Role: designated
Port id: 128.1000                              Port cost: 10000
Type: P2P    (configured:Auto  ) RSTP          Port Fast: Yes (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1000                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 1
BPDU: sent 9138497, received 0

Port Po2 enabled
State: disabled                                Role: disabled
Port id: 128.1001                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1001                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po3 enabled
State: disabled                                Role: disabled
Port id: 128.1002                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1002                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po4 enabled
State: disabled                                Role: disabled
Port id: 128.1003                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1003                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po5 enabled
State: disabled                                Role: disabled
Port id: 128.1004                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1004                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po6 enabled
State: disabled                                Role: disabled
Port id: 128.1005                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1005                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po7 enabled
State: disabled                                Role: disabled
Port id: 128.1006                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1006                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Port Po8 enabled
State: disabled                                Role: disabled
Port id: 128.1007                              Port cost: 20000
Type: N/A (configured:Auto  ) RSTP             Port Fast: No (configured:Auto)
Designated bridge Priority : 4096              Address: 70:c9:c6:f9:5c:27
Designated port id: 128.1007                   Designated path cost: 0
Guard root: Disabled                           BPDU guard: Disabled
Number of transitions to forwarding state: 0
BPDU: sent 0, received 0

Does this look good? Priorities of the access switches can be equal, right?

Seb Rupik · ‎12-24-2019

Hello again,

The bridge priorities look good to ensure the core stack remains the root bridge.

With the second core switch powered on, you say it had a bridge priority of 32768? When stacked, it should be reporting the same value as the master switch in the stack. If the two stack 'members' are reporting different STP bridge values then something it wrong.

What is the output of:

sh stack

sh stack links details

...from both switches?

Regarding the loopguard, you do not want to have that enabled on stacking ports between members. I don't have a 350X to check with, but if you have loopguard enabled globally I would disable it and configure it on a per-port basis. However with your topology loopguard should not be used on the core stack. Rootguard yes, but not loopguard.

cheers,

Seb.

IFM · ‎12-26-2019

Hi Seb,

yes. The second core switch had that bridge priority but since I set this manually to 4096 like on the other core everything seems to work.

Output:

sw-fra-c#sh stack

Topology is Chain
Units stack mode: Native

Unit Id MAC Address Role Network Uplink
Port Port
Type Type
------- ------------------- -------- ------- ------
1 70:c9:c6:f9:5c:27 master te none
2 70:c9:c6:f9:74:a1 backup te none

sw-fra-c#sh stack links details

Topology is Chain

UNIT ID Link Status Speed Neighbor Neighbor Neighbor
Unit ID Link MAC Address
------- -------- ---------- ----- -------- -------- -------------------
1 te23 Active 10G 2 te23 70:c9:c6:f9:74:a1
1 te24 Active 10G 2 te24 70:c9:c6:f9:74:a1
2 te23 Active 10G 1 te23 70:c9:c6:f9:5c:27
2 te24 Active 10G 1 te24 70:c9:c6:f9:5c:27

I now disabled loopback guard on my stacked core and enabled root guard on all ports connected to the access layer switches.

Best regards,

Hendrik