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.

Guide Contents
Troubleshooting Overview
Troubleshooting Installs, Upgrades, and Reboots
Troubleshooting Licensing
Troubleshooting VDCs
Troubleshooting CFS
Troubleshooting Ports
Troubleshooting vPCs {this section}
Troubleshooting VLANs
Troubleshooting STP
Troubleshooting Routing
Troubleshooting WCCP
Troubleshooting Memory
Before Contacting Technical Support
Troubleshooting Tools and Methodology


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

Verify that all vPC interfaces in a vPC domain are configured in the same virtual device context (VDC).

Verify that you have a separate vPC peer-link and peer-keepalive link infrastructure for each VDC deployed.

Verify that the vPC peer link exists between two 10-Gigabit Ethernet ports in dedicated mode.

Verify that you have attached all vPC devices using port channels to both vPC peer devices.

Verify that you have configured the peer-keepalive link before you configure the vPC peer link or the peer link will not come up.

Verify that you have first configured a port channel on each device and then configure the vPC domain.

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.

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.

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.

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.

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 
       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

Troubleshooting Ports

Further Reading

The following links contain further information on this topic from

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

vPC (Virtual Port-Channel) and the Nexus 5000 Platform

Blog on Cisco Nexus Features (VLANs, vPCs)

Rating: 3.6/5 (8 votes cast)

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