NEXUS: TROUBLESHOOTING VPC WITH EXAMPLES


TROUBLESHOOTING VPC

 

 

ISSUE MAY RELATE TO:

VDC, KEEPALIVE, PEER-LINK, SYSTEM PRIORITY, VPC NUMBER, VPC CONSISTENCY PARAMETERS, STP ROOT

 

VDC

To simplify, VDC is dividing the Single Physical device into number of Virtual devices

 

  1. All vPC interfaces in a vPC domain are configured in the same virtual device context (VDC)

 

  1. You have a separate vPC peer-link and peer-keepalive link infrastructure for each VDC deployed

 

KEEPALIVE

  1. Physical ports assigned to Keep Alive VRF should be up. In below example, port is Eth3/48

If peer-keep alive link is down, then the vPC peer-link will not come up.

 

  1. Verify that both the source and destination IP addresses used for the peer-keepalive messages are reachable from the VRF associated with the vPC peer-keepalive link

 

Example:

For making Peer Keep Alive connectivity up, we make dedicated VRF & assign physical ports of peer devices to these VRF

N7K1# sh vrf all

VRF-Name                           VRF-ID State   Reason

KEEPALIVE                                 3 Up     —

default                                      1 Up     —

management                             2 Up     —

N7K1# sh vrf int

Interface                  VRF-Name                       VRF-ID Site-of-Origin

port-channel110     KEEPALIVE                           3 —

N7K1# sh port-channel sum

Group Port-       Type     Protocol Member Ports

Channel

110 Po110(RU)   Eth     LACP     Eth3/48(P)

 

PEER LINK

Verify that the vPC peer-link is configured as a Layer 2 Port Channel trunk which only allows vPC VLANs

 

SYSTEM PRIORITY

If you manually configured the system priority, verify that you assigned the same priority value on both vPC peer devices

Example:

N7K1# sh vpc role

vPC Role status

vPC role                       : primary

Dual Active Detection Status   : 0

vPC system-mac                 : 00:23:04:ee:be:14

vPC system-priority             : 4000

vPC local system-mac           : e8:ed:f3:39:dd:41

vPC local role-priority         : 1000

 

VPC NUMBER

  1. 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.

 

VPC CONSISTENCY PARAMETERS

Check the show vpc consistency-parameters command to verify that both vPC peer devices have identical type-1 parameters

 

STP ROOT

  1. Verify that the primary vPC is the primary STP root and the secondary vPC is the secondary STP root

 

To simplify, out of two end devices of VPC, one must be acting as Primary & other must be acting as secondary

In our example, 7K1 is primary & 7K2 is secondary

So, In terms of STP, 7K1 must act as STP Root Bridge

If 7K1 is Root Bridge, then all its ports in VPC must be designated ports, which is shown below in example

 

Example

N7K1# sh vpc role

vPC Role status

vPC role                       : primary

N7K1# sh spanning-tree interface port-channel 100

Vlan             Role Sts Cost     Prio.Nbr Type

VLAN0001         Desg FWD 1         128.4195 (vPC peer-link) Network P2p

VLAN0320         Desg FWD 1         128.4195 (vPC peer-link) Network P2p

VLAN0696       Desg FWD 1         128.4195 (vPC peer-link) Network P2p

VLAN0697        Desg FWD 1         128.4195 (vPC peer-link) Network P2p

 

 

 

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