This section describes the different types of interfaces supported by the device. The rest of the chapter describes configuration procedures for physical interface characteristics.

Note	The stack ports on the rear of the stacking-capable devices are not Ethernet ports and cannot be configured.

Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs cannot exchange data without going through a routing device. With a standard Layer 2 device, ports in different VLANs have to exchange information through a router. By using the device with routing enabled, when you configure both VLAN 20 and VLAN 30 with an SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through the device with no need for an external router.

When the Network Advantage license is used on the device or the active device, the device uses the routing method to forward traffic between interfaces. If the Network Essentials license is used on the device or the active device, only basic routing (static routing and RIP) is supported. Whenever possible, to maintain high performance, forwarding is done by the device hardware. However, only IPv4 packets with Ethernet II encapsulation are routed in hardware.

The routing function can be enabled on all SVIs and routed ports. The device routes only IP traffic. When IP routing protocol parameters and address configuration are added to an SVI or routed port, any IP traffic received from these ports is routed.

The device supports these interface types:

• Physical ports: Device ports and routed ports

• VLANs: Switch virtual interfaces

• Port channels: EtherChannel interfaces

You can also configure a range of interfaces.

To configure a physical interface (port), specify the interface type, stack member number (only stacking-capable switches), module number, and device port number, and enter interface configuration mode.

• Type: Gigabit Ethernet (GigabitEthernet or gi) for 10/100/1000 Mbps Ethernet ports, 2.5-Gigabit Ethernet (TwoGigabitEthernet or tw) for 2.5 Gbps, 5-Gigabit Ethernet (FiveGigabitEthernet or fi) for 5 Gbps, 10-Gigabit Ethernet (TenGigabitEthernet or te) for 10 Gbps, 25-Gigabit Ethernet (TwentyFiveGigE or twe) for 25 Gbps, small form-factor pluggable (SFP) module Gigabit Ethernet and 10-Gigabit Ethernet interfaces and quad small-form-factor pluggable (QSFP) module 40-Gigabit Ethernet (FortyGigabitEthernet or fo) for 40 Gbps.

  Note	On a Cisco Catalyst 9300L Series Switch, the Type can be either Gigabit Ethernet or 10-Gigabit Ethernet.

• Stack member number: The number that identifies the device within the stack. The device number range is 1 to 8 and is assigned the first time the device initializes. The default device number, before it is integrated into a device stack, is 1. When a device has been assigned a stack member number, it keeps that number until another is assigned to it.

  You can use the switch port LEDs in Stack mode to identify the stack member number of a device.

• Module number: The module or slot number on the device: switch (downlink) ports are 0, and uplink ports are 1.

• Port number: The interface number on the device. The 10/100/1000 port numbers always begin at 1, starting with the far left port when facing the front of the device, for example, GigabitEthernet1/0/1 or GigabitEthernet1/0/8.

  On a device with SFP uplink ports, the module number is 1 and the port numbers restart. For example, if the device has 24 10/100/1000 ports, the SFP module ports are GigabitEthernet1/1/1 through GigabitEthernet1/1/4 or TenGigabitEthernet1/1/1 through TenGigabitEthernet1/1/4.

You can identify physical interfaces by physically checking the interface location on the device. You can also use the show privileged EXEC commands to display information about a specific interface or all the interfaces on the switch. The remainder of this chapter primarily provides physical interface configuration procedures.

These are examples of how to configure interfaces on stacking-capable and standalone device:

• To configure 10/100/1000 port 4 on a standalone device, enter this command:

  
  Device# configure terminal
  Device(config)# interface GigabitEthernet1/0/4
  
  

• To configure 10-Gigabit Ethernet port 1 on a standalone device, enter this command:

  
  
  Device# configure terminal
  Device(config)# interface TenGigabitEthernet 1/1/1
  
  

• To configure 10-Gigabit Ethernet port on stack member 3, enter this command:

  
  
  Device# configure terminal
  Device(config)# interface TenGigabitEthernet 3/1/1
  
  

• To configure the first SFP module (uplink) port on a standalone device, enter this command:

  
  
  Device# configure terminal
  Device(config)# interface GigabitEthernet 1/1/1
  
  

Cisco Catalyst 9300 Series Switches support breakout cables. These cables support 4x10 G by enabling a single 40-G QSFP+ interface to be split into four 10-G SFP+ interfaces and a single 100-G QSFP28 interface into four 25-G SFP28 interfaces.

Note	Breakout cable support is available only on the following switch models and network modules, with a few limitations.

To configure Layer 2 parameters, if the interface is in Layer 3 mode, you must enter the switchport interface configuration command without any parameters to put the interface into Layer 2 mode. This shuts down the interface and then re-enables it, which might generate messages on the device to which the interface is connected. When you put an interface that is in Layer 3 mode into Layer 2 mode, the previous configuration information related to the affected interface might be lost, and the interface is returned to its default configuration.

This table shows the Ethernet interface default configuration, including some features that apply only to Layer 2 interfaces.

Ethernet interfaces on the switch operate at 10, 100, 1000 Mbps, 2.5 Gbps, 5 Gbps, 10 Gbps and in either full-duplex or half-duplex mode. In full-duplex mode, two stations can send and receive traffic at the same time. Normally, 10-Mbps ports operate in half-duplex mode, which means that stations can either receive or send traffic.

Switch modules include Gigabit Ethernet (10/100/1000-Mbps) ports. The switch also includes multigigabit ethernet ports which support speeds up to 2.5 Gbps (100/1000/2500-Mbps), 5 Gbps (100/1000/2500/5000-Mbps), 10 Gbps (100/1000/2500/5000/10000-Mbps); SFP modules that support speeds up to 1 Gbps, SFP+ modules that support speeds up to 10 Gbps, SFP28 modules that support speeds up to 25 Gbps, QSFP modules that support speeds up to 40 Gbps.

Note	Cisco Catalyst 9300L Series Switches support only SFP uplink ports with speeds up to 1Gbps and SFP+ uplink ports with speeds up to 10 Gbps.

When configuring an interface speed and duplex mode, note these guidelines:

• Gigabit Ethernet (10/100/1000-Mb/s) ports support all speed options and all duplex options (auto, half, and full). However, Gigabit Ethernet ports operating at 1000 Mb/s and above do not support half-duplex mode.

  Multigigabit ethernet ports (2.5 Gb/s, 5Gb/s, 10 Gb/s) support all speed options but only support auto and full duplex mode. These ports do not support half-duplex mode at any speed.

  SFP ports operating at 1 Gb/s, SFP+ ports operating at 10 Gb/s, SFP28 ports operating at 25 Gb/s and QSFP ports operating at 40 Gb/s only no speed nonegotiate or speed nonegotiate . Duplex options are not supported.

  Note	SFP, SFP+ and SFP28 ports support speed (auto/10/100/100) and duplex (auto/full/half) options only if the 1000Base-T SFP or the GLC-GE-100FX modules are used.

  QSFP ports operating at 40 Gb/s support all speed options but only support auto and full duplex.

• If both ends of the line support autonegotiation, we highly recommend the default setting of auto negotiation.

• If one interface supports autonegotiation and the other end does not, configure duplex and speed on both interfaces; do not use the auto setting on the supported side.

• When STP is enabled and a port is reconfigured, the device can take up to 30 seconds to check for loops. The port LED is amber while STP reconfigures. As best practice, we suggest configuring the speed and duplex options on a link to auto or to fixed on both the ends. If one side of the link is configured to auto and the other side is configured to fixed, the link may or may not be up and this is expected.

Caution

Changing the interface speed and duplex mode configuration might shut down and re-enable the interface during the reconfiguration.

The device 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. You cannot delete interface VLAN 1.

  Note	When you create an SVI, it does not become active until it is associated with a physical port.

  When configuring SVIs, you can use the switchport autostate exclude command on a port to exclude that port from being included in determining SVI line-state. To disable autostate on the SVI, use the no autostate command on the SVI.

• 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.

A Layer 3 device 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 device or in a device stack. 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 device is using its maximum hardware resources, attempts to create a routed port or SVI have these results:

• If you try to create a new routed port, the device 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 device 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 device 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 device sends a message that this was due to insufficient hardware resources.

Note

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: 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. Furthermore, when you put an interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to the affected interface might be lost, and the interface is returned to its default configuration

The following procedure provides steps of how to set the interface speed and duplex parameters:

For information about device compatibility, see the Transceiver Module Group (TMG) Compatibility Matrix.