7 – Native Extended Layer 2

The diversity of services required in a cloud computing environment and the constraints related to the type of applications moving over the extended network require a set of diversified DCI solutions. Cisco offers three groups of technical solutions that meet these criteria:

Point-to-Point Interconnections: For point-to-point interconnections between two sites using a dedicated fiber or a protected dense wavelength-division multiplexing (DWDM8)mode, Cisco offers Multi-Chassis Ether Channel (MEC) solutions that allow multiple physical links of a Port Channel to be distributed over two different chassis. MEC is available through two approaches:

  • A single control plane managing the two chassis: This method is available on the Catalyst 6500 series with the function of Virtual Switching System (VSS).
  • An independent control plane: This option is available on Cisco Nexus 5000 and Cisco Nexus 7000 Series switches with the function of a virtual Port-Channel (vPC).

These options can provide active physical link and edge device redundancy to ensure the continuity of traffic between the remote sites, for type 1 and type 2 faults. Both approaches eliminate the use of the Spanning Tree protocol to control the loops. In addition, the MEC solution improves bandwidth utilization.

MEC Solution


Multiple Site Interconnections: For multi-site interconnections using optical links or using a DWDM service running in protected mode, FabricPath (TRILL) can quickly and seamlessly connect multiple remote sites in a fabric fashion, remove the extension of the Spanning Tree Protocol between remote data centers, and offer huge scalability compared to classical Ethernet. FabricPath is available on the Cisco Nexus 7000 Series Switches, with upcoming availability on Cisco Nexus 5500 Series9 Switches. FabricPath can also be used in a point-to-point model, which supports tying additional data centers into the cloud without impacting the production network or affecting existing connections.

Security: Traffic sent through the DCI Layer 2 extension can also be encrypted between a Cisco Nexus 7000 Series Switch deployed at the network edge using the Cisco feature called TrustSec (CTS). With CTS, encryption is performed by the hardware at line rate without impacting the performance or the latency of the traffic crossing the inter-site network. CTS offers a rich set of security services including the confidentiality of data transmitted over the WAN via a standard encryption mechanism (802.1AE).

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