NAD 3020 manual Recommended Topology

Design Guide

Network Topologies Using the Cisco Catalyst Blade Switch 3020

This section discusses the following physical topologies:

●Recommended topology: Classic V-shaped topology with Spanning Tree Protocol

●Alternative topology: Square topology with Spanning Tree Protocol

These network designs emphasize high availability in the data center by eliminating any single point of failure and by providing deterministic traffic patterns and predictable behavior during times of network convergence. The configuration example included uses a pair of Cisco Catalyst 6513 Switches as the aggregation layer platform. This Layer 2/Layer 3 switching platform supports the slot density and integrated network services required by data centers deploying blade systems. An HP c-Class BladeSystem with two Cisco Catalyst Blade Switch 3020s composes the Layer 2 access layer.

Recommended Topology

Typical deployment in the data center uses the classic triangle topology. This deployment model has no single point of failure. The Cisco Catalyst Blade Switch 3020s are dual homed to the aggregation layer, providing link redundancy. The Spanning Tree Protocol manages the physical loops created by the uplinks between the aggregation and access switches, facilitating a predictable and fast-converging topology.

RPVST+ fulfills the high-availability requirements of this design and is the recommended mode of spanning-tree operation. RPVST+ provides fast convergence (less than 1 second) in device or uplink failure scenarios. In addition, RPVST+ offers enhanced Layer 2 features for the access layer with integrated capabilities equivalent to PortFast, UplinkFast, and BackboneFast.

The connection between the two internal blade switches supports local traffic limited to the HP BladeSystem; for example, clustering applications or management traffic such as remotely mirrored (RSPAN) traffic. This connection does not carry a publicly accessible subnet (for example, a VLAN that exists on the uplinks to the aggregation switches). If it did, another set of interfaces would have to be accounted for in the Spanning Tree Protocol calculations. Therefore, to create a less-complex Spanning Tree Protocol domain, these cross-connect interfaces are removed from the equation by clearing the public VLANs from the links.

The HP c-Class BladeSystem server-blade NICs support the logical separation of VLANs by trunking, allowing each NIC to accommodate the public and the private VLANs on the Cisco Catalyst Blade Switch 3020s. In addition, full-height servers are dual homed to each of the two Cisco Catalyst Blade Switch 3020s in the HP BladeSystem. This structural design allows for the physical separation of public and private VLANs between two NICs homed to the same Cisco Catalyst Blade Switch 3020.

A series of network-convergence tests was performed to verify and characterize the high- availability features of the recommended design. These tests consisted of passing traffic between an external client device and the blade servers while monitoring packet loss. The following test cases were used:

●Uplink failure and recovery between switch A and the primary root

●Uplink failure and recovery between switch B and the primary root

●Switch A failure and recovery

●Switch B failure and recovery

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