4.2 Enabling Routing Between VLANs 4.2.2 Describing Configuration Commands for Inter-VLAN Communication on a Multilayer Switch The commands in Figure are used to configure inter-VLAN routing on a multilayer switch using SVIs. These commands are described in Figure .
Content 4.2 Enabling Routing Between VLANs 4.2.3 Configuring Inter-VLAN Routing on a Multilayer Switch To configure inter-VLAN routing on a Cisco Catalyst SVI, perform the steps in Figure . Figure describes each of these steps.
Content 4.2 Enabling Routing Between VLANs 4.2.4 Describing Routed Ports on a Multilayer Switch A routed switch port is a physical switch port on a multilayer switch that is capable of Layer 3 packet processing. A routed port is not associated with a particular VLAN, as contrasted with an access port or SVI. The switch port functionality is removed from the interface. A routed port behaves like a regular router interface, except that it does not support VLAN subinterfaces. Routed switch ports can be configured using most commands applied to a physical router interface, including the assignment of an IP address and the configuration of Layer 3 routing protocols. A routed switch port is a standalone port that is not associated with a VLAN, whereas an SVI is a virtual interface that is associated with a VLAN. SVIs generally provide Layer 3 services for devices connected to the ports of the switch where the SVI is configured. Routed switch ports can provide a Layer 3 path into the switch for a number of devices on a specific subnet, all of which are accessible from a single physical switch port. The number of routed ports and SVIs that can be configured on a switch is not limited by software. However, the interrelationship between these interfaces and other features configured on the switch may overload the CPU because of hardware limitations.
Content 4.2 Enabling Routing Between VLANs 4.2.5 Configuration of Routed Ports on a Multilayer Switch Routed switch ports are typically configured by removing the Layer 2 switch port capability of the switch port. On most switches, the ports are Layer 2 ports by default. On some switches, the ports are Layer 3 ports by default. The layer at which the port functions determines the commands that can be configured on the port.A routed port has the following characteristics and functions:
Content 4.2 Enabling Routing Between VLANs 4.2.6 Configuring Routed Ports on a Multilayer Switch To configure a routed port, perform the steps in Figure . Figure describes each of these steps.
Content 4.3 Deploying CEF-Based Multilayer Switching 4.3.1 Explaining Layer 3 Switch Processing Layer 3 switching refers to a class of high performance routers optimized for the campus LAN or intranet, providing both wire-speed Ethernet routing and switching services. A Layer 3 switch router performs the following three major functions: Compared to other routers, Layer 3 switch routers process more packets faster by using ASIC hardware instead of microprocessor-based engines. Layer 3 switch routers also improve network performance with two software functions: route processing and intelligent network services. Layer 3 switching software employs a distributed architecture in which the control path and data path are relatively independent. The control path code, such as routing protocols, runs on the route processor, whereas most of the data packets are forwarded by the Ethernet interface module and the switching fabric. Each interface module includes a microcoded processor that handles all packet forwarding. The control layer functions between the routing protocol and the firmware datapath microcode with the following primary duties: Layer 3 switching can occur at two different locations on the switch: Layer 3 switching uses one of these two methods, depending on the platform:
Content 4.3 Deploying CEF-Based Multilayer Switching 4.3.2 Explaining CEF-based Multilayer Switches Cisco Layer 3 devices can use a variety of methods to switch packets from one port to another. The most basic method of switching packets between interfaces is called process switching. Process switching moves packets between interfaces on a scheduled basis, based on information in the routing table and the Address Resolution Protocol (ARP) cache. As packets arrive, they are put in a queue to wait for further processing. When the scheduler runs, the outbound interface is determined, and the packet is switched. Waiting for the scheduler introduces latency. To speed the switching process, strategies exist to switch packets on demand as they arrive and to cache the information necessary to make packet-forwarding decisions. CEF uses these strategies to expediently switch data packets to their destination. It caches information generated by the Layer 3 routing engine. CEF caches routing information in one table (the FIB), and caches Layer 2 next-hop addresses for all FIB entries in an adjacency table. Because CEF maintains multiple tables for forwarding information, parallel paths can exist and enable CEF to load balance per packet. CEF operates in one of two modes. There is a wide range of CEF-based Cisco multilayer switches: The Cisco Catalyst 6500 is a modular switch in which the Multilayer Switch Feature Card