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Nexus 5K & 2K Link Aggregation (vPC)

Hi Guys,

Just want to get your expert opinion on this. I configured port-channel & vPC on two separate Nexus switch. The configuration is correct as the vPC is up and are port-channeling. The only thing I noticed is the aggregated bandwidth or link speed on the vPC as shown on the verification below. It does not show the aggregated BW which should be 2000000 Kbit in this case because I bundled two 1Gbe interfaces from diferent Nexus switches.

vPC is define as: "A virtual port channel (vPC) allows links that are physically connected to two different Cisco Nexus 5000 Series switches to appear as a single port channel to a third device."

My questions is, does vPC aggregates the bandwidth or speed accross multiple physical switches? Why it wasn't shown on the "show vpc" result as aggregated bandwidth?

Just curious and I wonder if I missed something on the configuration.

Configuration on Switch-1:

interface port-channel100
  switchport mode trunk
  vpc 100
  switchport trunk allowed vlan 12-14
  duplex full

interface Ethernet100/1/1
  switchport mode trunk
  switchport trunk allowed vlan 12-14
  duplex full
  channel-group 100

Configuration on Switch-2:

interface port-channel100
  switchport mode trunk
  vpc 100
  switchport trunk allowed vlan 12-14
  duplex full

interface Ethernet100/1/1
  switchport mode trunk
  switchport trunk allowed vlan 12-14
  duplex full
  channel-group 100

Verification on Switch-1:

N5K-01# show vpc statistics vpc 100

port-channel100 is up

vPC Status: Up, vPC number: 100

  Hardware: Port-Channel, address:

  Description:

  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA

  Port mode is trunk

  full-duplex, 1000 Mb/s

  Beacon is turned off

  Input flow-control is off, output flow-control is on

  Switchport monitor is off

  EtherType is 0x8100

  Members in this channel: Eth100/1/1

Verification on Switch-2:

N5K-02# show vpc statistics vpc 100
port-channel100 is up
vPC Status: Up, vPC number: 100
  Hardware: Port-Channel, address:
  Description:
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA
  Port mode is trunk
  full-duplex, 1000 Mb/s
  Beacon is turned off
  Input flow-control is off, output flow-control is on
  Switchport monitor is off
  EtherType is 0x8100
  Members in this channel: Eth100/1/1

I appreciate and welcomed your comments. Thanks.

Richard

Everyone's tags (2)
2 REPLIES
Cisco Employee

Nexus 5K & 2K Link Aggregation (vPC)

Hi

As it comes - nexus reports about aggregated bandwidth of local VPC members. SO if you'd have 2 1gig links on this chassis and 2 1gig links - on the other - total bandwidtch would be  2000000 Kbit.

Same behavior on n5k and n7k platforms.

As for aggregating the bandwidth - vpc works as portchannel - so traffic which came to vpc cluster will be balanced between vpc links.

That means that your downstream device will use whole bandwidth loadbalancing between port-chanel members.

HTH,

Alex

New Member

Nexus 5K & 2K Link Aggregation (vPC)

Remember a downstream device sees the two Nexus switches as a single logical device, but it still uses 'port-channel' and not 'virtual port-channel' to the upstream device. The vPC is only between the two Nexus 5k switches.

vPC actively forwards on both links. Hence it uses up all the uplink bandwidth.

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