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Spanning-tree between 4 connected switches

Boon Keat Gan
Level 1
Level 1

Hi All,

We try to create a new inter-office link. The new link is highlighted in red line below.

However, we keep received the flapping error message as follow. How can I troubleshot on this?

*Jan  4 19:05:04.850: %SW_MATM-4-MACFLAP_NOTIF: Host 28d2.4476.140a in vlan 17 is flapping between port Gi4/0/42 and port Gi4/0/44
*Jan  4 19:05:05.026: %SW_MATM-4-MACFLAP_NOTIF: Host 0013.2304.ea7f in vlan 25 is flapping between port Gi4/0/44 and port Gi4/0/42
*Jan  4 19:05:05.026: %SW_MATM-4-MACFLAP_NOTIF: Host 0013.2304.49e8 in vlan 25 is flapping between port Gi4/0/44 and port Gi4/0/42
*Jan  4 19:05:05.144: %SW_MATM-4-MACFLAP_NOTIF: Host 4055.3926.8dc1 in vlan 17 is flapping between port Gi4/0/44 and port Gi4/0/42
*Jan  4 19:05:05.144: %SW_MATM-4-MACFLAP_NOTIF: Host a01d.48f5.4a7b in vlan 17 is flapping between port Gi4/0/44 and port Gi4/0/42
*Jan  4 19:05:05.312: %SW_MATM-4-MACFLAP_NOTIF: Host 4055.3926.8dc1 in vlan 25 is flapping between port Gi4/0/42 and port Gi4/0/44
*Jan  4 19:05:05.312: %SW_MATM-4-MACFLAP_NOTIF: Host 4055.3926.8dc1 in vlan 2 is flapping between port Gi4/0/42 and port Gi4/0/44
*Jan  4 19:05:05.320: %SW_MATM-4-MACFLAP_NOTIF: Host 4055.3926.8dc1 in vlan 19 is flapping between port Gi4/0/44 and port Gi4/0/42

 

6 Replies 6

Akash Agrawal
Cisco Employee
Cisco Employee

Hi,

 

Please share output of "show spanning-tree vlan 17" from switch SW03, SW04 ,SW40 amd SW85. Also check on all switches if you are seeing any unusual logs related to link flap or spanning tree flap.

 

Regards,

Akash

Hi Akash,

Thanks for replied. I only check the link flapping error on SW85 using console cable. 

Please see below for the requested show spanning-tree vlan 17 result.

 

SW03# show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol rstp
  Root ID    Priority    4113
             Address     4055.3904.cc41
             This bridge is the root
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    4113   (priority 4096 sys-id-ext 17)
             Address     4055.3904.cc41
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Desg FWD 1         128.4096 (vPC peer-link) Network P2p
Eth7/18          Desg FWD 19        128.914  P2p Peer(STP)

 

SW04# show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol rstp
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        1
             Port        4096 (port-channel1)
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    8209   (priority 8192 sys-id-ext 17)
             Address     4055.3926.8dc1
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Root FWD 1         128.4096 (vPC peer-link) Network P2p
Eth7/17          Desg FWD 19        128.913  P2p Peer(STP)

SW40#show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol ieee
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        20
             Port        47 (GigabitEthernet0/47)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32785  (priority 32768 sys-id-ext 17)
             Address     001b.0cb9.9c00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/1            Desg FWD 4         128.1    Edge P2p
Gi0/2            Desg FWD 19        128.2    Edge P2p
Gi0/3            Desg FWD 4         128.3    Edge P2p
Gi0/4            Desg FWD 4         128.4    Edge P2p
Gi0/8            Desg FWD 4         128.8    Edge P2p
Gi0/16           Desg FWD 4         128.16   Edge P2p
Gi0/17           Desg FWD 4         128.17   Edge P2p
Gi0/18           Desg FWD 4         128.18   Edge P2p
Gi0/20           Desg FWD 4         128.20   Edge P2p
Gi0/21           Desg FWD 4         128.21   Edge P2p
Gi0/24           Desg FWD 19        128.24   Edge P2p
Gi0/25           Desg FWD 19        128.25   Edge P2p
Gi0/26           Desg FWD 19        128.26   Edge P2p
Gi0/27           Desg FWD 19        128.27   Edge P2p
Gi0/28           Desg FWD 4         128.28   Edge P2p
Gi0/29           Desg FWD 19        128.29   Edge P2p
Gi0/32           Desg FWD 4         128.32   Edge P2p
Gi0/33           Desg FWD 4         128.33   Edge P2p
Gi0/35           Desg FWD 4         128.35   Edge P2p
Gi0/37           Desg FWD 4         128.37   Edge P2p
Gi0/38           Desg FWD 4         128.38   Edge P2p
Gi0/40           Desg FWD 4         128.40   Edge P2p
Gi0/44           Desg FWD 4         128.44   Edge P2p
Gi0/45           Desg FWD 16384     128.45   P2p
Gi0/47           Root FWD 19        128.47   P2p
Gi0/49           Desg FWD 4         128.49   P2p
Gi0/50           Desg FWD 4         128.50   P2p
Gi0/52           Desg FWD 4         128.52   P2p

SW85#show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol ieee
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        19
             Port        204 (GigabitEthernet4/0/42)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32785  (priority 32768 sys-id-ext 17)
             Address     e05f.b9da.e780
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/1/1             Desg FWD 4         128.49   P2p
Gi3/1/1             Desg FWD 4         128.157  P2p
Gi3/1/2             Desg FWD 4         128.158  P2p
Gi4/0/42            Root FWD 19        128.204  P2p

Hi,

 

As of now you have shut down the port Gig4/0/44 and that is why it is loop free topology and all ports are either in Desg FWD or Root FWD. When all links are up, one link should be in blocking mode. I believe host whose mac is flapping (for exa. 28d2.4476.140a) nust be connected below SW40,(to one of SW41,SW42,SW43 or SW44). When frame comes to SW40, it should be received to SW85, either on Gig4/0/42 or Gig4/0/44. One path should be blocked status.

 

You can unshut link Gig40/44 on SW85 during MW and check status of spanning tree on all vlans. Any recent changes in topology or port-channel/VPC on nexus switches?

 

Regards,

Akash

Hi Akash,

There is no recent changes to the nexus switches. We are trying to implement a backup redundant link in case the main link is down.

Sorry to ask, what do you mean by MW?

MW = Maintenance window.

Noted that. I have enabled and capture the configuration result. Please see below. It is in Desg mode and not block. Can i manually change it to block mode?

 

SW03# show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol rstp
  Root ID    Priority    4113
             Address     4055.3904.cc41
             This bridge is the root
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    4113   (priority 4096 sys-id-ext 17)
             Address     4055.3904.cc41
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Desg FWD 1         128.4096 (vPC peer-link) Network P2p
Eth7/18          Desg FWD 19        128.914  P2p Peer(STP)

SW04# show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol rstp
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        1
             Port        4096 (port-channel1)
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    8209   (priority 8192 sys-id-ext 17)
             Address     4055.3926.8dc1
             Hello Time  2  sec  Max Age 20 sec  Forward Delay 15 sec

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Po1              Root FWD 1         128.4096 (vPC peer-link) Network P2p
Eth7/17          Desg FWD 19        128.913  P2p Peer(STP)

SW40#show spanning-tree vlan 17

VLAN0017
  Spanning tree enabled protocol ieee
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        20
             Port        47 (GigabitEthernet0/47)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32785  (priority 32768 sys-id-ext 17)
             Address     001b.0cb9.9c00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 15

Interface        Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Gi0/1            Desg FWD 4         128.1    Edge P2p
Gi0/2            Desg FWD 19        128.2    Edge P2p
Gi0/3            Desg FWD 4         128.3    Edge P2p
Gi0/4            Desg FWD 4         128.4    Edge P2p
Gi0/8            Desg FWD 4         128.8    Edge P2p
Gi0/17           Desg FWD 4         128.17   Edge P2p
Gi0/18           Desg FWD 4         128.18   Edge P2p
Gi0/20           Desg FWD 4         128.20   Edge P2p
Gi0/21           Desg FWD 4         128.21   Edge P2p
Gi0/24           Desg FWD 19        128.24   Edge P2p
Gi0/25           Desg FWD 19        128.25   Edge P2p
Gi0/26           Desg FWD 19        128.26   Edge P2p
Gi0/27           Desg FWD 19        128.27   Edge P2p
Gi0/28           Desg FWD 4         128.28   Edge P2p
Gi0/29           Desg FWD 19        128.29   Edge P2p
Gi0/32           Desg FWD 4         128.32   Edge P2p
Gi0/35           Desg FWD 4         128.35   Edge P2p
Gi0/37           Desg FWD 4         128.37   Edge P2p
Gi0/38           Desg FWD 4         128.38   Edge P2p
Gi0/40           Desg FWD 4         128.40   Edge P2p
Gi0/42           Desg FWD 4         128.42   Edge P2p
Gi0/43           Desg FWD 19        128.43   Edge P2p
Gi0/44           Desg FWD 4         128.44   Edge P2p
Gi0/45           Desg FWD 16384     128.45   P2p
Gi0/47           Root FWD 19        128.47   P2p
Gi0/49           Desg FWD 4         128.49   P2p
Gi0/50           Desg FWD 4         128.50   P2p
Gi0/52           Desg FWD 4         128.52   P2p

SW85# show spanning-tree vlan 17
VLAN0017
  Spanning tree enabled protocol ieee
  Root ID    Priority    4113
             Address     4055.3904.cc41
             Cost        19
             Port        204 (GigabitEthernet4/0/42)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32785  (priority 32768 sys-id-ext 17)
             Address     e05f.b9da.e780
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  15  sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/1/1             Desg FWD 4         128.49   P2p
Gi3/1/1             Desg FWD 4         128.157  P2p
Gi3/1/2             Desg FWD 4         128.158  P2p
Gi4/0/42            Root FWD 19        128.204  P2p
Gi4/0/44            Desg FWD 16384     128.206  P2p

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