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Community Member

Spanning Tree BDPU Guard.HSRP/ OSPF

I had issue come up yesterday and unfortunately i was unable to trouble shoot this root cause so i am getting second hand information so bare with me.

Issue 1: users pluggd 4 (non cisco)switches into the network daisy chained them together. This caused the ort to reconize a BDPU and since we have BDPU guard turned on it thus shut the port down as expected.

Issue 2. Once BDPU guard shut down the port HSRP started flapping from active to standby state

Issue 3. once the HSRP started flapping OSPF started reconverging

My question is what would cause Issue 2 and 3? BDPU guard should have just shut down the port and network would have been okay but that was not the case.

Here is an output of the lof that was generated:

1,x.x.62.3,HSRP-4-DUPADDR,,May,16,10:18:44,May,16,10:18:44,Duplicate address x.x.1.3onVlan101 sourced by 0000.0c07.ac00

71,x.x.63.7,SPANTREE-2-RX_PORTFAST,Port2/38,May,16,10:20:49,May,16,10:25:32,Received BPDU on PortFast enable port. Disabling 2/38

3,x.x.62.3,HSRP-4-DUPADDR,,May,16,10:22:59,May,16,10:23:00,Duplicate address x.x.1.3onVlan101 sourced by 0000.0c07.ac00

2,x.x.62.3,HSRP-6-STATECHANGE,Vlan168,May,16,10:27:32,May,16,10:29:20,Vlan168 Grp 0 state Standby->Active

2,x.x.62.3,HSRP-6-STATECHANGE,Vlan200,May,16,10:27:32,May,16,10:29:20,Vlan200 Grp 0 state Standby->Active

2,x.x.62.3,HSRP-6-STATECHANGE,Vlan102,May,16,10:27:32,May,16,10:29:20,Vlan102 Grp 0 state Standby->Active

5,x.x.62.3,HSRP-6-STATECHANGE,Vlan120,May,16,10:27:32,May,16,10:29:20,Vlan120 Grp 0 state Standby->Active

4,x.x.62.3,HSRP-6-STATECHANGE,Vlan340,May,16,10:27:32,May,16,10:29:20,Vlan340 Grp 0 state Standby->Active

15,x.x.62.2,HSRP-6-STATECHANGE,Vlan165,May,16,10:27:34,May,16,10:29:22,Vlan165 Grp 0 state Standby->Active

2,x.x.62.2,HSRP-6-STATECHANGE,Vlan63,May,16,10:27:34,May,16,10:29:22,Vlan63 Grp 0 state Standby->Active

19,x.x.62.2,HSRP-6-STATECHANGE,Vlan101,May,16,10:27:34,May,16,10:29:23,Vlan101 Grp 0 state Standby->Active

2,x.x.62.3,HSRP-6-STATECHANGE,Vlan166,May,16,10:27:34,May,16,10:29:20,Vlan166 Grp 0 state Standby->Active

8,x.x.62.3,HSRP-6-STATECHANGE,Vlan340,May,16,10:27:42,May,16,10:28:51,Vlan340 Grp 0 state Active->Speak

3,x.x.62.2,HSRP-6-STATECHANGE,Vlan165,May,16,10:27:54,May,16,10:28:51,Vlan165 Grp 0 state Active->Speak

8,x.x.62.2,OSPF-5-ADJCHG,,May,16,10:27:56,May,16,10:29:59,Process 300 Nbr x.x.62.5 on GigabitEthernet1/0/2 from FULL to DOWN Neighbor Down: Dead timer expired

5,x.x.62.3,OSPF-5-ADJCHG,,May,16,10:27:56,May,16,10:30:00,Process 300 Nbr x.x.62.5 on GigabitEthernet1/0/1 from FULL to DOWN Neighbor Down: Dead timer expired

2,x.x.62.2,HSRP-6-STATECHANGE,Vlan101,May,16,10:27:57,May,16,10:28:51,Vlan101 Grp 0 state Active->Speak

1,x.x.62.2,HSRP-6-STATECHANGE,Vlan63,May,16,10:28:51,May,16,10:28:51,Vlan63 Grp 0 state Active->Speak

1,x.x.62.3,HSRP-6-STATECHANGE,Vlan166,May,16,10:28:51,May,16,10:28:51,Vlan166 Grp 0 state Active->Speak

1,x.x.62.3,HSRP-6-STATECHANGE,Vlan168,May,16,10:28:52,May,16,10:28:52,Vlan168 Grp 0 state Active->Speak

Community Member

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

Perhaps it is something to do with interface tracking in HSRP ?

Community Member

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

I do not have HSRP tracking turned on..

Also this happened on a 4006 switch

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

How many active ports are in the VLAN? Is it possible just this one port was active and when BPDU Guard shut the port down no more ports were active in this VLAN so the SVI interface went down as well which in turn caused HSRP to flip and also OSPF to recalculate?


Community Member

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

What you are showing here is the normal state change of the current router from standby to active. I would assume the former active router fell out of play because it was on the losing end of the daisy-chained switches. Was that the case here? Did it return to standby state later?

Community Member

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

HSRP should only change state should the keepalives not be received or if there was an interface being tracked. Since you mentioned it is not the latter one, then it seems that the keep alives got lost somewhere when the port disabled. I would check the cabling and L2 paths between the HRSP peers.

Did the HSRP recover eventually back to normal?

Community Member

Re: Spanning Tree BDPU Guard.HSRP/ OSPF

Well it turns out that we are spannng a vlan across multiple switches and when the user plugged the switches into each other they looped them some how and caused the VLAN to start flapping thus causing HSRP to bounce back between stanby and active thus OSPF would have to keep reconverging everytime the HSRP change state.

When the support engineer got onto the switch and disabled the port on the 4006 the problem cleared up. So I guess I need to understand why BPDU guard did not error disable this port and stop the flapping.

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