Cisco Datacenter: vPC ( Single and Double Sided vPC)

Lets talk about the two different scenarios in Cisco Datacenter environment. The two different concept of vPC called single-sided vPC and Dual sided vPC.

We have two different deployment scenarios for vPC in the datacenter as

• In the single datacenter environment we can use Single-sided vPC (access layer or aggregation layer) or we can go with the scenario Double-sided vPC, also called multilayer vPC (access layer using vPC interconnected to aggregation layer using vPC)
• In the multi datacenter environment we can have Multilayer vPC for Aggregation and DCI or we can have and Dual Layer 2 /Layer 3 Pod Interconnect.

Let's start discussion on every deployment methods



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 anything like L2 switches, rack mount or blade servers , Load balancers, firewalls or any storage devices. The end device which is an access device will have to support the port-channel connection between them. The Bundling can be LACP mode active, LACP mode passive and static bundling- mode on. There are some recommendations using LACP protocol connecting to the vPC domains.

• vPC with Cisco Nexus M1 Series module line-card: 16 active member ports (8 on peer device 1 and 8 on peer device 2)
• vPC with Cisco Nexus F1/F2 Series module line card: 32 active member ports (16 on peer device 1 and 16 on peer device 2)

Fig 1.1- vPC Deployment Scenarios

Double-Sided vPC: 
In Dual sided vPC where you have the two different vPC domain from distribution to Access layer parent switch and other vPC domain from parent access switch to the FEX devices you can say. vPC domain at the bottom is used for active/active connectivity from endpoint 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

we can further discuss on Multilayer vPC for Aggregation and DCI in another post. Keep connected and supported.