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This chapter contains the following sections:
Information About the Basic Interface Parameters
For the vEthernet, Ethernet, and management interfaces, you can configure the description parameter to provide a name for the interface. Using a unique name for each interface allows you to quickly identify the interface when you are looking at a listing of multiple interfaces.
By default, the description for vEthernet interfaces is automatically formatted to contain information about the connected device. The description for a virtual Network Interface Card (vNIC), for example, contains the VM name and network adapter number. You keep this default description or you can override it with a description of your choosing.
The speed and duplex modes are interrelated for each Ethernet and management interface. By default, each interface autonegotiates its speed and duplex modes with the other interface, but you can change these settings. If you change the settings, be sure to use the same speed and duplex mode settings on both interfaces or use autonegotiation for at least one of the interfaces.
The maximum transmission unit (MTU) size specifies the maximum frame size that an Ethernet port can process. For transmissions to occur between two ports, you must configure the same MTU size for both ports. A port drops any frames that exceed its MTU size.
By default, the MTU size for each port is 1500 bytes, which is the IEEE 802.3 standard for Ethernet frames. Larger MTU sizes are possible for more efficient processing of data with less overhead. The larger frames, called jumbo frames, can be up to 9000 bytes in size, which is also the fixed system jumbo MTU size in the Cisco Nexus 1000V.
The administrative-status parameter determines whether an interface is up or down. When an interface is administratively down, it is disabled and unable to transmit data. When an interface is administratively up, it is enabled and able to transmit data.
The Cisco Discovery Protocol (CDP) is a Layer 2 protocol that enables two devices that run CDP to learn about each other. You can use CDP to troubleshoot the network by displaying information about the neighboring devices that are linked through each interface. By default, CDP is enabled.
A port channel is an aggregation of multiple physical interfaces that comprise a logical interface. You can bundle up to eight individual interfaces into a port channel to provide increased bandwidth and redundancy. Port channeling also load balances traffic across these physical interfaces. The port channel stays operational if at least one physical interface within the port channel is operational.
Any configuration changes that you apply to the port channel are applied to each interface member of that port channel.
Interface parameters have the following configuration guidelines and limitations:
Note |
The device cannot automatically negotiate the Ethernet port speed and duplex modes if the connecting port is configured to a value other than auto. |
Note |
Changing the Ethernet port speed and duplex mode configuration might shut down and reenable the interface. |
Configuring the Basic Interface Parameters
You can specify an interface to configure.
Log in to the CLI in EXEC mode.
This example shows how to specify an interface to configure:
switch# configure terminal switch(config)# interface ethernet 2/1 switch(config-if)# show interface ethernet 2/1 switch(config-if)#
You can add a description to an Ethernet, vEthernet, or management interface.
This example shows how to set the interface description to Ethernet port 24 on module 3:
switch# configure terminal switch(config)# interface ethernet 3/24 switch(config-if)# description Ethernet port 24 on module 3 switch(config-if)#
You can configure the interface speed and duplex modes.
Note |
The interface speed that you specify can affect the duplex mode used for an interface, so you should set the speed before setting the duplex mode. If you set the speed for autonegotiation, the duplex mode is automatically set to be autonegotiated. If you specify a speed of 10 Mbps or 100 Mbps, the port is automatically configured to use half-duplex mode, but you can specify full-duplex mode instead. If you specify a speed of 1000 Mbps (1 Gbps) or faster, full duplex is automatically used. |
This example shows how to set the interface description to Ethernet port 24 on module 3:
switch# configure terminal switch(config)# interface ethernet 2/1 switch(config-if)# speed 1000 switch(config-if)# duplex full switch(config-if)# show interface mgmt0 switch(config-if)#
You can configure the size of the maximum transmission unit (MTU) for a Layer 2 Ethernet interface.
This example shows how to configure the Ethernet interface 3/1 with the default MTU size of 1500 bytes:
switch# configure terminal switch# interface ethernet 3/1 switch(config-if)# mtu 1500 switch(config-if)#
You can shut down and restart Ethernet or management interfaces.
This example shows how to configure the Ethernet interface 3/1 with the default MTU size of 1500 bytes:
switch# configure terminal switch(config)# interface ethernet 3/1 switch(config-if)# shutdown switch(config-if)# no shutdown switch(config-if)#
You can enable or disable the Cisco Discovery Protocol (CDP) for Ethernet and management interfaces.
This example shows how to enable CDP for Ethernet port 3/1:
switch# configure terminal switch(config)# interface ethernet 3/1 switch(config-if)# cdp enable switch(config-if)#
This example shows how to disable CDP for Ethernet port 3/1:
n1000v# configure terminal switch(config)# interface ethernet 3/1 switch(config-if)# no cdp enable switch(config-if)#
You can clear the Ethernet, vEthernet, and management interface counters.
Log in to the CLI in EXEC mode, configuration mode, or interface configuration mode.
This example shows how to clear and reset the counters on Ethernet port 5/5:
switch# clear counters ethernet 5/5 switch#
Use one of the following commands to verify the configuration:
Command | Purpose |
---|---|
show cdp |
Displays the CDP status. |
show interface interface |
Displays the configured states of one or all interfaces. |
show interface brief |
Displays a table of interface states. |
show interface switchport |
Displays the status of Layer 2 ports. |
Feature Name |
Releases |
Feature Information |
---|---|---|
System jumbo MTU |
4.2(1)SV1(4) |
The system jumbo MTU is fixed at 9000 and cannot be changed. |
Interface MTU |
4.2(1)SV1(4) |
The interface MTU can be configured as a value between 1500 and 9000. |
Basic interface parameters |
4.0(4)SV1(1) |
This feature was introduced. |