Cisco 3560G 48TS Software Configuration Guide - Page 235

Chapter 10 Configuring Interface Characteristics Configuring Layer 3 Interfaces Configuring Layer 3 Interfaces The Catalyst 3560 switch supports these types of Layer 3 interfaces: • SVIs: You should configure SVIs for any VLANs for which you want to route traffic. SVIs are created when you enter a VLAN ID following the interface vlan global configuration command. To delete an SVI, use the no interface vlan global configuration command. Note When you create an SVI, it does not become active until it is associated with a physical port. For information about assigning Layer 2 ports to VLANs, see Chapter 12, "Configuring VLANs." • Routed ports: Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface configuration command. • Layer 3 EtherChannel ports: EtherChannel interfaces made up of routed ports. EtherChannel port interfaces are described in Chapter 29, "Configuring EtherChannels." A Layer 3 switch can have an IP address assigned to each routed port and SVI. There is no defined limit to the number of SVIs and routed ports that can be configured in a switch. However, the interrelationship between the number of SVIs and routed ports and the number of other features being configured might have an impact on CPU usage because of hardware limitations. If the switch is using maximum hardware resources, attempts to create a routed port or SVI have these results: • If you try to create a new routed port, the switch generates a message that there are not enough resources to convert the interface to a routed port, and the interface remains as a switchport. • If you try to create an extended-range VLAN, an error message is generated, and the extended-range VLAN is rejected. • If the switch is notified by VLAN Trunking Protocol (VTP) of a new VLAN, it sends a message that there are not enough hardware resources available and shuts down the VLAN. The output of the show vlan user EXEC command shows the VLAN in a suspended state. • If the switch attempts to boot up with a configuration that has more VLANs and routed ports than hardware can support, the VLANs are created, but the routed ports are shut down, and the switch sends a message that this was due to insufficient hardware resources. All Layer 3 interfaces require an IP address to route traffic. This procedure shows how to configure an interface as a Layer 3 interface and how to assign an IP address to an interface. Note If the physical port is in Layer 2 mode (the default), you must enter the no switchport interface configuration command to put the interface into Layer 3 mode. Entering a no switchport command disables and then re-enables the interface, which might generate messages on the device to which the interface is connected. Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 interface: Step 1 Step 2 Command Purpose configure terminal Enter global configuration mode. interface {{fastethernet | gigabitethernet} interface-id} Enter interface configuration mode, and enter the | {vlan vlan-id} | {port-channel port-channel-number} interface to be configured as a Layer 3 interface. 78-16156-01 Catalyst 3560 Switch Software Configuration Guide 10-19