Switched Campus Network Designs - Cisco Catalyst 2000 Configuration Handbook

pool together into a VSS 1440. The two switches connect with 10 GbE links called
Virtual Switch Links (VSL). When a VSS 1440 is created, it acts as a single virtual
Catalyst switch.
Note The Catalyst 6500 chassis was classified as end of sale and was replaced with the
Catalyst 6500-E chassis. The E chassis supports all existing line cards but was enhanced to
provide a better power bus for PoE and power supplies. The E chassis also provides the fol-
lowing benefits from the non-E chassis: support for 80 Gbps per slot, increase cooling
capacity per slot to accommodate high-performance line cards, and adds a redundant con-
trol channel to improve high availability (HA) capabilities of the switch.

2-2: Switched Campus Network Designs

When you design a switched network, you must consider many things. Adding to or
redesigning a large enterprise or campus network can seem complex or overwhelming.
An accepted, organized approach to switched network design can simplify the design
process and make the network more efficient and scalable.
This section is organized as a quick reference "checklist" of guidelines, rules of thumb,
and ideas to help you think through the overall network architecture and configuration.
Many of the checklist items include a reference to the appropriate sections of this book
that deal with the switch features.
Segment LANs into the smallest collision domains possible by using LAN switches.
1.
Organize your enterprise network into a hierarchical structure.
2.
A network designed around a layered structure gives the foundation for predictable
behavior, consistent latency (number of switch hops) from anywhere in the network,
and scalability. If the network needs to be expanded, you can add more switch
blocks into the existing structure.
Figure 2-1 shows the basic network hierarchy divided into three distinct layers:
Access layer: Consists of switches that connect to the end users
■
Distribution layer: Consists of switches that aggregate traffic from the access layer
■
Core layer: Consists of switches that aggregate traffic from the distribution layers
■
Tip In small- to medium-sized enterprise networks, the distribution layer can be omitted.
The access layer switches uplink directly into the core layer, which is referred to as a
collapsed core design.
Chapter 2: Switch Functionality 17