between ports without Layer 2 protocol translation.

Gigabit Ethernet: An extension of the IEEE 802.3 Ethernet standard, Gigabit Ethernet increases speed tenfold over that of Fast Ethernet, to 1000 Mbps, or 1 gigabit per second (Gbps). IEEE 802.3z specifies operations over fiber optics, and IEEE 802.3ab specifies operations over twisted-pair cable.

10-Gigabit Ethernet: 10-Gigabit Ethernet was formally ratified as an IEEE 802.3 Ethernet standard in June 2002. This technology is the next step for scaling the performance and functionality of an enterprise. With the deployment of Gigabit Ethernet becoming more common, 10-Gigabit will become the norm for uplinks.

EtherChannel: This feature provides link aggregation of bandwidth over Layer 2 links between two switches. EtherChannel bundles individual Ethernet ports into a single logical port or link, providing aggregate bandwidth of up to 1600 Mbps (eight 100 Mbps links, full duplex) or up to 16 Gbps (8-Gigabit links, full duplex) between two Cisco Catalyst switches. All interfaces in each EtherChannel bundle must be configured with similar speed, duplex, and VLAN membership.

Figure discusses the use of each interconnection technology in the Campus Infrastructure module.

Content 2.1 Implementing Best Practices for VLAN Topologies 2.1.4 Determining Equipment and Cabling Needs There are four objectives in the design of any high-performance network: security, availability, scalability, and manageability. The ECNM, when implemented properly, provides the framework to meet these objectives. In the migration from a current network infrastructure to the ECNM, a number of infrastructure changes may be needed, including the replacement of current equipment and existing cable plant. This list describes the equipment and cabling decisions that should be considered when altering infrastructure.

Replace hubs and legacy switches with new switches at the Building Access layer. Select equipment with the appropriate port density at the access layer to support the current user base while preparing for growth. Some designers begin by planning for about 30 percent growth. If the budget allows, use modular access switches to accommodate future expansion. Consider planning for support of inline power and quality of service (QoS) if IP telephony may be implemented in the future.
When building the cable plant from the Building Access layer to the Building Distribution layer devices, remember that these links carry aggregate traffic from the end nodes at the access layer to the building distribution switches. Ensure that these links have adequate bandwidth capability. EtherChannel bundles can be used here to add bandwidth as necessary.
At the Building Distribution layer, select switches with adequate performance to handle the load of the current Building Access layer. Also plan some port density for adding trunks later to support new access layer devices. The devices at this layer should be multilayer (Layer 2/Layer 3) switches that support routing between the workgroup VLANs and network resources. Depending on the size of the network, the building distribution layer devices may be fixed chassis or modular. Plan for redundancy in the chassis and in the connections to the access and core layers, as the business objectives dictate.
The campus backbone equipment must support high-speed data communications between other submodules. Be sure to size the backbone for scalability and plan on redundancy.

Cisco has online tools to assist designers in making the proper selection of devices and uplink ports based on business and technology needs. Cisco suggests oversubscription ratios that can be used to plan bandwidth requirements between key devices on a network with average traffic flows.

Access to distribution layer links: The oversubscription ratio should be no higher than 20:1. That is, the link can be 1/20 of the total bandwidth available cumulatively to all end devices using that link.
Distribution to core links: The oversubscription ratio should be no higher than 4:1.
Between core devices: There should be little to no oversubscription planning. That is, the links between core devices should be able to carry traffic at the speed represented by the aggregate number bandwidth of all the distribution uplinks into the core.

CAUTION: These ratios are appropriate for estimating average traffic from access layer, end-user devices. They are not accurate for planning oversubscription from the server farm or edge distribution modules. They are also not accurate for planning bandwidth needed on access switches hosting typical user applications with high bandwidth consumption (for example, non-client server databases or multimedia flows to unicast addresses). Using QoS end to end prioritizes the traffic that would need to be dropped in the event of congestion.

Content 2.1 Implementing Best Practices for VLAN Topologies 2.1.5 Considering Traffic Source to Destination Paths Figure lists different types of traffic that may exist on the network and require consideration before device placement and VLAN configuration. Figure describes the specific traffic types. Considering IP Telephony The size of an enterprise network drives the design and placement of certain types of devices. If the network is designed according to the ECNM, there will be distinct devices separating the access, distribution, and backbone areas of the network. The network design and the types of applications supported determine where certain traffic sources are located. Multicast and IP telephony applications share some common traffic types. Specifically, if a Cisco CallManager is providing music on hold, it may need to multicast that traffic stream. Consider the following points when determining where to place the servers:

Cisco CallManager servers must be accessible throughout the network at all times. Ensure that there are redundant NICs in the publisher and subscriber servers and redundant connections between those NICs and the upstream switch from the server. It is recommended that voice traffic be configured on its own VLAN. Cisco CallManagers are typically located within the Server Farm block in the ECNM design.
VLAN trunks must be configured appropriately to carry IP telephony traffic throughout the network or to specific destinations.

When you deploy voice, it is recommended that you enable two VLANs at the access layer: a native VLAN for data traffic and a voice VLAN. Separate voice and data VLANs are recommended for the following reasons:

Address space conservation and voice device protection from external networks
QoS trust boundary extension to voice devices
Protection from malicious network attacks
Ease of management and configuration

Considering IP Multicast Traffic The multilayer campus design is ideal for control and distribution of IP multicast traffic. The Layer 3 multicast control is provided by Protocol Independent Multicast (PIM) routing protocol. Multicast control at the wiring closet is provided by Internet Group Membership Protocol (IGMP) snooping or Cisco Group Multicast Protocol (CGMP). Multicast control is extremely important because of the large amount of traffic involved when several high-bandwidth multicast streams are provided. Consider the following when designing the network for multicast traffic:

IP multicast servers may exist within a server farm or be distributed throughout the network at appropriate locations.
Select distribution layer switches to act as PIM rendezvous points (RPs) and place them where they are central to the location of the largest distribution of receiving nodes. RPs are typically used to temporarily connect multicast sources and receivers.

Web Links For more information on CallManager, such as the publisher and subscriber functionality, see the