Nexus Basic Design Aspects in a multi-tier Architecure
Where The Nexus and MDS Switches Fit In a Data Center according to Cisco Validated designs and best practices? This section answers this question describing the typical placement of the Cisco Nexus and MDS Families series switches in a Cisco Data Center. It should be noticed that every design may have specific requirements, so a mixed architecture can be deployed.
Single-Tier Data Center
The Cisco Nexus 7000 Series switches can be used for both access and core layer connectivity in the single-tier data center architecture. The access layer can provide connectivity for the servers with low cost 48-port Gigabit Ethernet linecards or with the 32-port 10 Gigabit Ethernet linecards if 10GE interfaces is required.
The single-tier data center architecture can be expanded by connecting Cisco Nexus 2000 fabric extenders (FEX) to Cisco Nexus 7000 Series switches to provide connectivity for the servers. It should be mentioned that the Nexus 2000 can be used only to provide connectivity to servers or end hosts and should not be connected with Layer 2 devices e.g. blade switches. This setup would provide a Top-of-Rack (ToR) solution for the servers with a Cisco Nexus 7000 Series switch acting as the aggregation point collapsing the access, aggregation, & core layers. It should be highlighted that if the budget is limited then the Nexus 9000 is the best alternative to the Nexus 7000. A pair of Nexus 5000 switches in a single-tier setup as parent switch with several FEX is a common low cost solution for small Data Centers.
Two-Tier Data Center
The two-tier data center option connects the Cisco Nexus 2000 Fabric Extenders to an upstream Cisco Nexus 5000 Series switch. The Cisco Nexus 5000 function as End-of-Row (EOR) access switch and is connected via active multiple links (portchannel) to a pair of Cisco Nexus 7000 switches. The following topology illustrates an access layer and a collapsed core/ distribution layer.
Three-Tier Data Center
The three-tier data center is similar to the aforementioned two-tier data center architecture regarding the access layer and the placement of the Nexus 5000 and Nexus 2000 switches. However, multiple Nexus 7000 switches are used to the aggregation/distribution layer. The core layer is provided by a pair of Cisco Nexus 7000 Series switches (check figure below).
The Nexus 9000 switches due to their exceptional performance and comprehensive feature set switches are versatile platforms that can be deployed in multiple scenarios such as layered access-aggregation-core designs, Leaf-and-spine architecture and Compact aggregation-layer solutions.
Regarding the Storage (SAN) architecture, the Cisco MDS 9000 Series Multilayer Switches can provide SAN connectivity at the access layer and the core layer. Connectivity between the SAN and LAN infrastructures to support FCoE can be supported through the Cisco Nexus 7000 or 5000 series switches and the Cisco MDS 9000 Series. It is very common at the modern Data Centers with Cisco equipment the converge FC and LAN traffic by utilizing the FCoE technology. So, the number of connections, the SAN equipment and the complexity is drastically reduced. Finally, the MDS SAN switches are not mandatory to a small-sized SAN architecture if the Nexus Swithces e.g. N5k are equipped with the necessary license.