Cisco Nexus 7000 Series NX-OS Troubleshooting Guide -- Troubleshooting vPCs
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This article describes how to troubleshoot virtual Port Channel(vPC) problems on a Cisco NX-OS device.
Contents |
Information About Troubleshooting vPCs
A vPC allows links that are physically connected to two different Cisco Nexus 7000 Series devices to appear as a single port channel by a third device.
See the Configuring vPC chapter in the Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide for more information on vPCs.
Initial Troubleshooting Checklist
Begin troubleshooting vPC issues by checking the following issues first:
| Checklist | Check off |
|---|---|
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Verify that all vPC interfaces in a vPC domain are configured in the same virtual device context (VDC). | |
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Verify that you have a separate vPC peer-link and peer-keepalive link infrastructure for each VDC deployed. | |
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Verify that the vPC peer link exists between two 10-Gigabit Ethernet ports in dedicated mode. | |
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Verify that you have attached all vPC devices using port channels to both vPC peer devices. | |
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Verify that you have configured the peer-keepalive link before you configure the vPC peer link or the peer link will not come up. | |
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Verify that you have first configured a port channel on each device and then configure the vPC domain. | |
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Verify that you have manually configured the STP root, the Layer 3 VLAN network interface, and HSRP active (if required) to conform to the primary/secondary mapping of each of the vPC peer devices. | |
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Verify that you have configured a VLAN network interface on each peer device and that the interface is connected to the same VLAN on each device. Also, each VLAN interface must be in the same administrative and operational mode. | |
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Verify that both the source and destination IP addresses used for the peer-keepalive messages are unique in your network and these IP addresses are reachable from the VRF associated with the vPC peer-keepalive link. | |
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If you manually configured the system priority, verify that you assigned the same priority value on both vPC peer devices. If the vPC peer devices have different system priority values, vPC will not come up. | |
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Verify that the vPC number that you assigned to the port channel that connects to the downstream device from the vPC peer device is identical on both vPC peer devices. |
Verifying vPCs Using the CLI
To verify vPCs using the CLI, follow these steps:
1. Use the show running-config vpc command to verify the vPC configuration.
2. Use the show vpc consistency-parameters interface to verify that the vPC peers have the required identical configurations.
3. Use the show vpc brief command to verify that none of the vPC interfaces are in suspend mode.
4. Use the show vpc peer-keepalive command to verify the status of the vPC peers.
5. Use the show cfs status commands to verify that distribution over Ethernet is enabled.
6. If you enable STP, use the show spanning-tree command on both sides of the vPC peer link to verify that the following STP parameters are identical:
- BPDU Filter
- BPDU Guard
- Cost
- Link type
- Priority
- VLANs (PVRST+)
Received Type 1 Configuration Element Mismatch
You may have a problem where you cannot bring up a vPC link because of a type 1 configuration element mismatch.
| Symptom | Possible Cause | Solution | |
|---|---|---|---|
|
Received a type 1 configuration element mismatch. |
The vPC peer ports or membership ports do not have identical configurations. |
Use the show vpc consistency-parameters interface command to determine where the configuration mismatch occurs. |
Example: show vpc consistency-parameters Command Output
This example shows how to display the vPC consistency parameters on a port channel:
switch# show vpc consistency-parameters interface po 10
Legend:
Type 1 : vPC will be suspended in case of mismatch
Name Type Local Value Peer Value
------------- ---- ---------------------- -----------------------
STP Mode 1 Rapid-PVST Rapid-PVST
STP Disabled 1 None None
STP MST Region Name 1 "" ""
STP MST Region Revision 1 0 0
STP MST Region Instance to 1
VLAN Mapping
STP Loopguard 1 Disabled Disabled
STP Bridge Assurance 1 Enabled Enabled
STP Port Type 1 Normal Normal
STP MST Simulate PVST 1 Enabled Enabled
Allowed VLANs - 1-10,15-20,30,37,99 1-10,15-20,30,37,99
Cannot Enable the vPC Feature
You may receive an error when you enable the vPC feature.
| Symptom | Possible Cause | Solution |
|---|---|---|
|
Cannot enable the vPC feature. |
The hardware is incompatible with the vPC. |
Use the show module command to determine the hardware version of each 10/100/1000 Ethernet module. The hardwere version must be 1.3 or later to enable the vPC feature. |
Example: show module Command Output
This example shows how to display the module hardware version:
switch# show module Mod Ports Module-Type Model Status --- ----- -------------------------------- ------------------ ------------ 2 32 10 Gbps Ethernet Module N7K-M132XP-12 ok 3 48 10/100/1000 Mbps Ethernet Module N7K-M148GT-11 ok 5 0 Supervisor module-1X N7K-SUP1 active * 6 0 Supervisor module-1X N7K-SUP1 ha-standby 10 32 10 Gbps Ethernet Module N7K-M132XP-12 ok Mod Sw Hw --- -------------- ------ 2 4.1(5) 1.2 3 4.1(5) 1.0 >>> Must be 1.3 or later.
See Also
Further Reading
The following links contain further information on this topic from Cisco.com:
Virtual PortChannels: Building Networks without Spanning Tree Protocol (Cisco White Paper)
Configuring vPCs (Cisco Nexus 7000 Series Interfaces Configuration Guide)
Nexus 5000 Virtual PortChannel Quick Configuration Guide
External Links
The following links contain content developed by external authors. Cisco does not review this content for accuracy.
Our Nexus Data Center Network - To vPC or not to vPC
Nexus 7000 Virtual Portchannel Part 1
Nexus 7000 Virtual Portchannel Part 2
Nexus 7000 Virtual Portchannel Part 3
