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Finding the root cause of Spanning-Tree recalculations (on Cisco Nexus 9000s)
VLAN load sharing on Metro-E links between two Juniper EX 4200Cisco 2960 Portfast ports generate Spanning Tree TCNHow can I determine the STP designated bridge on Cisco IOS?Why showing IEEE Spanning Tree protocolCisco proprietary protocol - Spanning TreeHow do modern switches forward ethernet frames logically?Finding the optimum root bridge for a spanning treeSpanning tree root bridge process validationAdding new switch to Spanning Tree networkCisco nexus spanning-tree logging to syslog
I have a nagging Rapid PVST problem on some Nexus 9000 switches. Rapid-PVST keeps recalculating 3 to 5 times an hour. We have in this topology (summarized):
Edge Router Access Layer
+-------------+ +-------------+
| | Eth1/28 Eth1/54 | |
| Nexus9000_1 +-------------------------+ Nexus9000_2 |
| | Vlan350 | |
+-------------+ dot1q Trunk +-------------+
|Eth1/45 (dot1q trunk)
|
Something_Important
SHOW OUTPUT: Nexus9000_1
Nexus9000_1# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1348 last change occurred 0:35:39 ago <---
from Ethernet1/28 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
SHOW OUTPUT: Nexus9000_2
Nexus9000_2# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1157 last change occurred 0:35:39 ago <---
from Ethernet1/54 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
BACKGROUND
The reason I found the STP recalculations is because we got so many complaints about the device connected to Nexus9000_2 Eth1/45 having 30-ish second outages over and over again. Configuring Nexus9000_2 Eth1/45 as spanning-tree port type edge trunk made the problem much less visible because STP moves into a forwarding state much faster with that port-type.
I checked and know that the interfaces in this diagram are not flapping.
QUESTION
Each of those switches says it received a topology change notification (TCN) from the other switch. That's not very helpful... and I don't want to band-aid the problem with spanning-tree port type edge trunk on port Eth1/45.
What is the best way to find the root cause of these STP topology changes using the tools available on Nexus 9000 switches?
Please don't respond with show spanning-tree internal event-history all or other show spanning-tree internal commands without explaining what exactly to look for in those commands.
cisco spanning-tree cisco-nexus
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
add a comment |
I have a nagging Rapid PVST problem on some Nexus 9000 switches. Rapid-PVST keeps recalculating 3 to 5 times an hour. We have in this topology (summarized):
Edge Router Access Layer
+-------------+ +-------------+
| | Eth1/28 Eth1/54 | |
| Nexus9000_1 +-------------------------+ Nexus9000_2 |
| | Vlan350 | |
+-------------+ dot1q Trunk +-------------+
|Eth1/45 (dot1q trunk)
|
Something_Important
SHOW OUTPUT: Nexus9000_1
Nexus9000_1# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1348 last change occurred 0:35:39 ago <---
from Ethernet1/28 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
SHOW OUTPUT: Nexus9000_2
Nexus9000_2# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1157 last change occurred 0:35:39 ago <---
from Ethernet1/54 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
BACKGROUND
The reason I found the STP recalculations is because we got so many complaints about the device connected to Nexus9000_2 Eth1/45 having 30-ish second outages over and over again. Configuring Nexus9000_2 Eth1/45 as spanning-tree port type edge trunk made the problem much less visible because STP moves into a forwarding state much faster with that port-type.
I checked and know that the interfaces in this diagram are not flapping.
QUESTION
Each of those switches says it received a topology change notification (TCN) from the other switch. That's not very helpful... and I don't want to band-aid the problem with spanning-tree port type edge trunk on port Eth1/45.
What is the best way to find the root cause of these STP topology changes using the tools available on Nexus 9000 switches?
Please don't respond with show spanning-tree internal event-history all or other show spanning-tree internal commands without explaining what exactly to look for in those commands.
cisco spanning-tree cisco-nexus
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09
add a comment |
I have a nagging Rapid PVST problem on some Nexus 9000 switches. Rapid-PVST keeps recalculating 3 to 5 times an hour. We have in this topology (summarized):
Edge Router Access Layer
+-------------+ +-------------+
| | Eth1/28 Eth1/54 | |
| Nexus9000_1 +-------------------------+ Nexus9000_2 |
| | Vlan350 | |
+-------------+ dot1q Trunk +-------------+
|Eth1/45 (dot1q trunk)
|
Something_Important
SHOW OUTPUT: Nexus9000_1
Nexus9000_1# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1348 last change occurred 0:35:39 ago <---
from Ethernet1/28 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
SHOW OUTPUT: Nexus9000_2
Nexus9000_2# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1157 last change occurred 0:35:39 ago <---
from Ethernet1/54 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
BACKGROUND
The reason I found the STP recalculations is because we got so many complaints about the device connected to Nexus9000_2 Eth1/45 having 30-ish second outages over and over again. Configuring Nexus9000_2 Eth1/45 as spanning-tree port type edge trunk made the problem much less visible because STP moves into a forwarding state much faster with that port-type.
I checked and know that the interfaces in this diagram are not flapping.
QUESTION
Each of those switches says it received a topology change notification (TCN) from the other switch. That's not very helpful... and I don't want to band-aid the problem with spanning-tree port type edge trunk on port Eth1/45.
What is the best way to find the root cause of these STP topology changes using the tools available on Nexus 9000 switches?
Please don't respond with show spanning-tree internal event-history all or other show spanning-tree internal commands without explaining what exactly to look for in those commands.
cisco spanning-tree cisco-nexus
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
I have a nagging Rapid PVST problem on some Nexus 9000 switches. Rapid-PVST keeps recalculating 3 to 5 times an hour. We have in this topology (summarized):
Edge Router Access Layer
+-------------+ +-------------+
| | Eth1/28 Eth1/54 | |
| Nexus9000_1 +-------------------------+ Nexus9000_2 |
| | Vlan350 | |
+-------------+ dot1q Trunk +-------------+
|Eth1/45 (dot1q trunk)
|
Something_Important
SHOW OUTPUT: Nexus9000_1
Nexus9000_1# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1348 last change occurred 0:35:39 ago <---
from Ethernet1/28 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
SHOW OUTPUT: Nexus9000_2
Nexus9000_2# sh spanning-tree vlan 350 detail | i from|topology|VLAN
VLAN0350 is executing the rstp compatible Spanning Tree protocol
Number of topology changes 1157 last change occurred 0:35:39 ago <---
from Ethernet1/54 <---
Times: hold 1, topology change 35, notification 2
Timers: hello 0, topology change 0, notification 0
... Output snipped ...
BACKGROUND
The reason I found the STP recalculations is because we got so many complaints about the device connected to Nexus9000_2 Eth1/45 having 30-ish second outages over and over again. Configuring Nexus9000_2 Eth1/45 as spanning-tree port type edge trunk made the problem much less visible because STP moves into a forwarding state much faster with that port-type.
I checked and know that the interfaces in this diagram are not flapping.
QUESTION
Each of those switches says it received a topology change notification (TCN) from the other switch. That's not very helpful... and I don't want to band-aid the problem with spanning-tree port type edge trunk on port Eth1/45.
What is the best way to find the root cause of these STP topology changes using the tools available on Nexus 9000 switches?
Please don't respond with show spanning-tree internal event-history all or other show spanning-tree internal commands without explaining what exactly to look for in those commands.
cisco spanning-tree cisco-nexus
cisco spanning-tree cisco-nexus
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
edited May 10 at 22:06
Mike Pennington
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
asked May 9 at 21:30
Mike PenningtonMike Pennington
27.1k1167140
27.1k1167140
Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09
add a comment |
Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09
Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09
Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09
add a comment |
1 Answer
1
active
oldest
votes
In my case, I was able to solve the problem by turning on these debugs on Nexus9000_2:
debug spanning-tree rstp interface eth1/54debug spanning-tree event interface eth1/54debug spanning-tree bpdu_rx interface eth1/54
The next time a BPDU triggered a calculation, the debug gave me detailed information on what was happening on the switchport.
The output of this command was also useful: sh spanning-tree internal event-history all | begin VLAN0350
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpcpeer-switchconfigured on a non-RPVST root switch
– Mike Pennington
May 10 at 17:02
add a comment |
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1 Answer
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active
oldest
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
In my case, I was able to solve the problem by turning on these debugs on Nexus9000_2:
debug spanning-tree rstp interface eth1/54debug spanning-tree event interface eth1/54debug spanning-tree bpdu_rx interface eth1/54
The next time a BPDU triggered a calculation, the debug gave me detailed information on what was happening on the switchport.
The output of this command was also useful: sh spanning-tree internal event-history all | begin VLAN0350
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpcpeer-switchconfigured on a non-RPVST root switch
– Mike Pennington
May 10 at 17:02
add a comment |
In my case, I was able to solve the problem by turning on these debugs on Nexus9000_2:
debug spanning-tree rstp interface eth1/54debug spanning-tree event interface eth1/54debug spanning-tree bpdu_rx interface eth1/54
The next time a BPDU triggered a calculation, the debug gave me detailed information on what was happening on the switchport.
The output of this command was also useful: sh spanning-tree internal event-history all | begin VLAN0350
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpcpeer-switchconfigured on a non-RPVST root switch
– Mike Pennington
May 10 at 17:02
add a comment |
In my case, I was able to solve the problem by turning on these debugs on Nexus9000_2:
debug spanning-tree rstp interface eth1/54debug spanning-tree event interface eth1/54debug spanning-tree bpdu_rx interface eth1/54
The next time a BPDU triggered a calculation, the debug gave me detailed information on what was happening on the switchport.
The output of this command was also useful: sh spanning-tree internal event-history all | begin VLAN0350
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
In my case, I was able to solve the problem by turning on these debugs on Nexus9000_2:
debug spanning-tree rstp interface eth1/54debug spanning-tree event interface eth1/54debug spanning-tree bpdu_rx interface eth1/54
The next time a BPDU triggered a calculation, the debug gave me detailed information on what was happening on the switchport.
The output of this command was also useful: sh spanning-tree internal event-history all | begin VLAN0350
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
edited May 10 at 2:56
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
answered May 9 at 22:22
Mike PenningtonMike Pennington
27.1k1167140
27.1k1167140
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpcpeer-switchconfigured on a non-RPVST root switch
– Mike Pennington
May 10 at 17:02
add a comment |
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpcpeer-switchconfigured on a non-RPVST root switch
– Mike Pennington
May 10 at 17:02
2
2
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
Do tell what the ultimate problem was!
– Ron Trunk
May 10 at 1:49
vpc
peer-switch configured on a non-RPVST root switch– Mike Pennington
May 10 at 17:02
vpc
peer-switch configured on a non-RPVST root switch– Mike Pennington
May 10 at 17:02
add a comment |
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Do they actually recalculate the spanning tree, or are they just flooding another switch's TC flagged BPDU? (while flushing their CAM tables)
– Marc 'netztier' Luethi
May 10 at 5:09