Cisco Nexus vPC Benefits and Deployment Scenarios

Benefits of vPC

vPC is a virtualization technology that presents both Cisco Nexus 7000 Series paired devices as a unique Layer 2 logical node to access layer devices or endpoints. vPC belongs to Multichassis EtherChannel [MCEC] family of technology.

​A virtual port channel (vPC) allows links that are physically connected to two different Cisco Nexus 7000 Series devices to appear as a single port channel to a third device. The third device can be a switch, server, or any other networking device that supports link aggregation technology.
 ​
vPC provides the following technical benefits:



● Eliminates Spanning Tree Protocol (STP) blocked ports
● Uses all available uplink bandwidth
● Allows dual-homed servers to operate in active-active mode
● Provides fast convergence upon link or device failure
● Offers dual active/active default gateways for servers

By using vPC, users get the immediate operational and architectural advantages:
● Simplifies network design
● Build highly resilient and robust Layer 2 network
● Enables seamless virtual machine mobility and server high-availability clusters
● Scales available Layer 2 bandwidth, increasing bisectional bandwith
● Grows the size of the Layer 2 network

Components of vPC

NX-OS Version Requirement for vPC

 vPC technology is supported since NX-OS 4.1.3. (i.e since the inception of NEXUS 7000 
platform).
 NX-OS appropriate version depends on line cards configuration (M1, F1 or F2), chassis 
type (7010, 7018 or 7009) and Fabric Module generation (FM generation 1 [46Gbps per 
module] or generation 2 [110Gbps per module]).

NX-OS License Requirement for vPC
​ vPC feature is included in the base NX-OS software license.
​ ​Hot Standby Router Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), Link 
Aggregation Control Protocol (LACP) are also included in this base license.

The 2 common deployment scenarios using vPC technology are listed as below:
​● Inside Data Center:
​◦ Single-sided vPC (access layer or aggregation layer)
​◦ Double-sided vPC, also called multilayer vPC (access layer using vPC interconnected to aggregation layer using vPC)
● Across Data Center i.e vPC for Data Center Interconnect (DCI):
◦ Multilayer vPC for Aggregation and DCI
◦ Dual Layer 2 /Layer 3 Pod Interconnect

Single-Sided vPC



In single-sided vPC, access devices are directly dual-attached to pair of Cisco Nexus 7000 Series 
Switches forming the vPC domain.

The access device can be any endpoint equipement (L2 switch, rack-mount server, blade server, 
firewall, load balancer, network attached storage [NAS] device). Only prerequisite for the access 
​device is to support port-channeling (or link aggregation) technology:
● LACP mode active
● LACP mode passive
​● Static bundling (mode ON)

Beginning with Cisco NX-OS Software Release 4.1(3)N1(1a), the Cisco Nexus 5000 Series is capable of supporting 16 active member ports per port-channel. Cisco Nexus 5000 Series to a vPC domain gives a compelling topology where vPC can be sized up to 160 Gbps (16 x 10-Gbps ports).

Double-Sided vPC
This topology superposes two layers of vPC domain and the bundle 
between vPC domain 1 and vPC domain 2 is by itself a vPC.

​vPC domain at the bottom is used for active/active connectivity from enpoint devices 
to network access layer.

​vPC domain at the top is used for active/active FHRP in the L2/L3 boundary 
​aggregation layer.

Benefits of double-sided vPC over single-sided vPC topology are listed below:
​● Enables a larger Layer 2 domain.
​● Provides a higher resilient architecture. In double-sided vPC, two access switches 
are connected to two aggregation switches whereas in single-sided vPC, one access switch 
is connected to two aggregation switches.
​● Provides more bandwidth from the access to aggregation layer. Using a Cisco Nexus F1 or F2 Series modules line card for vPC and Cisco Nexus 5000 Series Switches with Release 4.1(3)N1(1a) or later, a vPC with 32 active member ports (that is, 320 Gbps) can be instantiated.

Multilayer vPC for Aggregation and DCI

​

vPC provides capabilities to build a loop-free topology, and as such it makes the technology a good fit for Data Center Interconnect (DCI) deployments. In this scenario, a dedicated layer of vPC domain (adjacent to aggregation layer which also runs vPC) is used to interconnect the 2 data centers together.​