Virtual Port Channel

This design showcases a back-to-back vPC (Virtual Port Channel) topology utilizing Cisco Nexus switches. In a back-to-back vPC setup, two pairs of vPC domains are interconnected, allowing redundancy and efficient traffic distribution without the reliance on STP (Spanning Tree Protocol) to block redundant paths. The diagram includes two vPC domains: Domain 11 (Nexus 101 and Nexus 102) in the core and two access-layer vPC domains, Domain 12 (Nexus 201 and Nexus 202) and Domain 13 (Nexus 301 and Nexus 302), which are connected to the core via vPC links.

Core Layer (vPC Domain 11):
The core layer consists of Nexus 101 and Nexus 102, configured in vPC Domain 11. These switches are connected using a vPC peer link (Po11), composed of four 100Gb DAC cables, ensuring high-speed interconnection and synchronization. A dedicated vPC keepalive link is used to monitor the health of the vPC peers. These switches manage the interconnection between the access-layer domains, handling significant traffic loads while maintaining redundancy.

Access Layers (vPC Domain 12 and Domain 13):
The access layer includes two separate vPC domains, Domain 12 (Nexus 201 and Nexus 202) and Domain 13 (Nexus 301 and Nexus 302). Each domain has a vPC peer link (Po12 and Po13, respectively) with two 40Gb DAC cables, along with keepalive links for health monitoring. These switches provide connectivity for servers or endpoints in their respective domains.

The back-to-back vPC design interconnects the access-layer vPC domains to the core layer using aggregated 10Gb interfaces in Port Channels Po21 and Po31, respectively. This ensures high availability and balanced traffic distribution across the uplinks. Each access-layer switch connects to both core switches, creating multiple active-active paths, eliminating any single point of failure while providing fault tolerance.

Technical Benefits:
High Availability: The design eliminates single points of failure with redundant paths between core and access layers.
Active-Active Traffic Flow: vPC allows links to operate in an active-active state, maximizing bandwidth utilization.
Reduced Convergence Times: By avoiding STP-blocked links, the design ensures faster network convergence in case of link or node failures.
Scalability: The design can easily accommodate additional switches or servers by expanding the existing vPC domains or adding new ones.
This design is ideal for environments requiring robust redundancy, high throughput, and minimal downtime, such as data centers or enterprise networks.

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