Table Of Contents
Configuring Basic Interface Parameters
Information About the Basic Interface Parameters
Unidirectional Link Detection Parameter
UDLD Aggressive and Nonaggressive Modes
Prerequisites for Configuring the Basic Interface Parameters
Configuring the Basic Interface Parameters
Specifying the Interfaces to Configure
Configuring the MDIX Parameter
Configuring the Debounce Timer
Configuring the Interface Speed and Duplex Mode
Configuring the Interface MTU Size
Configuring the System Jumbo MTU Size
Configuring the Throughput Delay
Shutting Down and Activating the Interface
Device: Device Details: MTU Settings Section
Port: Port Details: Basic Settings Section
Port: Port Details: Port Mode Settings Section
Port: Port Details: Advanced Settings Section
Configuring Basic Interface Parameters
This chapter describes how to configure the basic interface parameters. These parameters are shared by multiple interfaces.
This chapter includes the following sections:
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Information About the Basic Interface Parameters
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Note
Information About the Basic Interface Parameters
This section includes the following topics:
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Description
For the Ethernet and management interfaces, you can configure the description parameter to provide a recognizable 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.
For information on setting the description parameter for port-channel interfaces, see the "Configuring a Port-Channel Description" section on page 5-18. For information on configuring this parameter for other interfaces, see the "Configuring the Description" section.
Beacon
The beacon mode allows you to identify a physical port by flashing its link state LED with a green light. By default, this mode is disabled. To identify the physical port for an interface, you can activate the beacon parameter for the interface.
For information on configuring the beacon parameter, see the "Configuring the Beacon Mode" section.
MDIX
The medium dependent interface crossover (MDIX) parameter enables or disables the detection of a crossover connection between devices. This parameter applies only to copper interfaces. By default, this parameter is enabled.
Debounce Timer
The debounce timer delays notification of a link change, which can decrease traffic loss due to network reconfiguration. You can configure the debounce timer separately for each Ethernet port and specify the delay time in milliseconds. By default, this parameter is set for 100 milliseconds.
Caution
For information on configuring the debounce-timer parameters, see the "Configuring the Debounce Timer" section.
Speed Mode and Duplex Mode
The speed mode and duplex mode are interrelated for each Ethernet and management interface. By default, each of these interfaces autonegotiates its speed and duplex mode 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 setting on both interfaces, or use autonegotiation for at least one of the interfaces. Table 2-1 shows the settings that work for each type of Ethernet and management interface.
Table 2-1 Speed- and Duplex-Mode Settings Used for Ethernet and Management Interfaces
32-port 10 GE Ethernet
Auto1
Auto1
10,000
Full
48-port 10/100/1000 Ethernet
Auto1
Auto1
1000
Full
10 or 100
Half
1000
Auto1 or full
1000
Full
100
Auto1 or half
100
Half
Full
100
Full
10
Auto1 or half
10
Half
Full
10
Full
Management
Auto1
Auto1
1000
Full
10 or 100
Half
1000
Auto1 or full
1000
Full
100
Auto1 or half
100
Half
Full
100
Full
10
Auto1 or half
10
Half
Full
10
Full
1 Default setting
For information on setting the speed mode and duplex mode for port-channel interfaces, see the "Configuring the Speed and Duplex Settings for a Port-Channel Interface" section on page 5-18. For information on setting the speed and duplex speed for other interfaces, see the "Configuring the Interface Speed and Duplex Mode" section.
Flow Control
When the receive buffer for an Ethernet port that runs 1 Gbps or faster fills, flow control enables that port to send an IEEE 802.3x pause frame to the transmitting port to request it to stop transmitting data for a specified amount of time. Transmitting ports, running at any speed, can receive the pause frames to stop their transmission of data.
To allow flow control to work between two ports, you must set the corresponding receive and send flow control parameters for both ports as enabled or desired. When you set the parameter to enabled, the send or receive flow-control function is activated regardless of the setting of the other port. When you set the parameter to desired, the send or receive flow-control function is activated if you set the corresponding flow-control state of the other port to enabled or desired. If you set one of the flow control states to disabled, flow control is disabled for that transmission direction. To see how the different port flow-control states affect the link flow-control state, see Table 2-2.
For information on setting the flow-control parameters, see the "Configuring the Flow Control" section.
Port MTU Size
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, each port has an MTU of 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 9216 bytes in size, which is also the default system jumbo MTU size.
On a Layer 3 interface, you can configure an MTU size between 576 and 9216 bytes. You can configure up to 64 MTU settings for each I/O module.
Note
For a Layer 2 port, you can configure an MTU size that is either the system default (1500 bytes) or the system jumbo MTU size (initially 9216 bytes).
Note
For information on setting the MTU size, see the "Configuring the MTU Size" section.
Bandwidth
Ethernet ports have a fixed bandwidth of 1,000,000 Kb at the physical level. Layer 3 protocols use a bandwidth value that you can set for calculating their internal metrics. The value that you set is used for informational purposes only by the Layer 3 protocols—it does not change the fixed bandwidth at the physical level. For example, the Interior Gateway Routing Protocol (IGRP) uses the minimum path bandwidth to determine a routing metric, but the bandwidth at the physical level remains 1,000,000 Kb.
For information on configuring the bandwidth parameter for port-channel interfaces, see the Chapter 5, "Configuring Port Channels.". For information on configuring the bandwidth parameter for other interfaces, see the "Configuring the Bandwidth" section.
Throughput Delay
Specifying a value for the throughput-delay parameter provides a value used by Layer 3 protocols; it does not change the actual throughput delay of an interface. The Layer 3 protocols can use this value to make operating decisions. For example, the IGRP can use the delay setting to differentiate between a satellite link and a land link. The delay value that you set is in the tens of microseconds.
For information on configuring the bandwidth parameter for port-channel interfaces, see the Chapter 5, "Configuring Port Channels.". For information on configuring the throughput-delay parameter, see the "Configuring the Throughput Delay" section.
Administrative Status
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.
For information on configuring the administrative status parameter for port channel interfaces, see the "Shutting Down and Restarting the Port-Channel Interface" section on page 5-17. For information on configuring the administrative-status parameter for other interfaces, see the "Shutting Down and Activating the Interface" section.
Unidirectional Link Detection Parameter
This section includes the following topics:
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UDLD Overview
The Cisco-proprietary Unidirectional Link Detection (UDLD) protocol allows devices that are connected through fiber-optic or copper (for example, Category 5 cabling) Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. When a device detects a unidirectional link, UDLD shuts down the affected LAN port and alerts the user. Unidirectional links can cause a variety of problems, including spanning tree topology loops.
UDLD is a Layer 2 protocol that works with the Layer 1 protocols to determine the physical status of a link. At Layer 1, autonegotiation takes care of physical signaling and fault detection. UDLD performs tasks that autonegotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected LAN ports. When you enable both autonegotiation and UDLD, Layer 1 and Layer 2 detections work together to prevent physical and logical unidirectional connections and the malfunctioning of other protocols.
A unidirectional link occurs whenever traffic transmitted by the local device over a link is received by the neighbor but traffic transmitted from the neighbor is not received by the local device. If one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up. In this case, the logical link is undetermined, and UDLD does not take any action. If both fibers are working normally at Layer 1, then UDLD at Layer 2 determines whether those fibers are connected correctly and whether traffic is flowing bidirectionally between the correct neighbors. This check cannot be performed by autonegotiation, because autonegotiation operates at Layer 1.
The Nexus 7000 Series device periodically transmits UDLD frames to neighbor devices on LAN ports with UDLD enabled. If the frames are echoed back within a specific time frame and they lack a specific acknowledgment (echo), the link is flagged as unidirectional and the LAN port is shut down. Devices on both ends of the link must support UDLD in order for the protocol to successfully identify and disable unidirectional links.
Note
Figure 2-1 shows an example of a unidirectional link condition. Device B successfully receives traffic from device A on the port. However, device A does not receive traffic from device B on the same port. UDLD detects the problem and disables the port.
Figure 2-1 Unidirectional Link
Default UDLD Configuration
Table 2-3 shows the default UDLD configuration.
For information on configuring the UDLD for the device and its port, see the "Configuring the UDLD Mode" section.
UDLD Aggressive and Nonaggressive Modes
UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive mode is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops receiving UDLD frame, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.
To prevent spanning tree loops, nonaggressive UDLD with the default interval of 15 seconds is fast enough to shut down a unidirectional link before a blocking port transitions to the forwarding state (with default spanning tree parameters).
When you enable the UDLD aggressive mode, the following occurs:
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In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic from being discarded.
Note
Port Channel Parameters
A port channel is an aggregation of 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.
You can create a Layer 2 port channel by bundling compatible Layer 2 interfaces, or you can create Layer 3 port channels by bundling compatible Layer 3 interfaces. You cannot combine Layer 2 and Layer 3 interfaces in the same port channel.
Any configuration changes that you apply to the port channel are applied to each interface member of that port channel.
For information on port channels and for information on configuring port channels, see Chapter 5, "Configuring Port Channels."
Licensing Requirements
The interface command and its sub commands do not require licenses.
Prerequisites for Configuring the Basic Interface Parameters
Before you begin configuring the basic interface parameters, make sure that you are in the correct VDC. To change the VDC, choose Virtual Devices from the Feature Selector pane.
Guidelines and Limitations
Follow these guidelines and limitations for configuring the basic interface parameters:
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By default, each port is a Layer 3 interface.
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Caution
Configuring the Basic Interface Parameters
When you configure an interface, you must specify the interface before you can configure its parameters.
The following sections explain how to specify the interface and configure each of its basic parameters:
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Specifying the Interfaces to Configure
Before you can configure the parameters for one or more interfaces of the same type, you must specify the type and the identities of the interfaces. Table 2-4 shows the interface types and identities that you should use for specifying the Ethernet and management interfaces.
Table 2-4 Information Needed to Identify an Interface for Configurations
Ethernet
I/O module slot numbers and port numbers on the module.
Management
0 (for port 0)
To verify the current configuration of interfaces, you can display their properties.
You can choose an interface and see its parameter values in the Details pane.
DETAILED STEPS
To specify the interfaces to configure, follow these steps:
Step 1
a.
b.
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c.
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d.
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The devices with the interface type that you specified appear in the Summary pane.
Figure 2-2 shows the three Feature Selector items to choose to specify an interface type.
Figure 2-2 Specifying an Interface Type
Step 2
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Figure 2-3 Specifying a Port for an Ethernet Interface
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Figure 2-4 Specifying a Device for a Management Interface
Tabs and sections for displaying detailed information for the interface that you specified appear in the Details pane.
Configuring the Description
You can provide textual interface descriptions for the Ethernet and management interfaces. Descriptions can be a maximum of 80 case-sensitive alphanumeric characters.
DETAILED STEPS
To provide and interface description for Ethernet and management interfaces, follow these steps:
Step 1
Step 2
The devices with the interface type that you specified appear in the Summary pane.
Step 3
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Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
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Tabs appear for the device information in the Details pane. The Details tab is active but its sections are not expanded.
Step 4
The Basic Settings shows the basic parameters.
Step 5
Step 6
Configuring the Beacon Mode
You can enable the beacon mode for an Ethernet port to flash its LED to confirm its physical location.
DETAILED STEPS
To enable or disable the beacon mode, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
The Basic Settings section shows the basic parameters.
Step 4
Step 5
Configuring the MDIX Parameter
If you need to detect the type of connection (crossover or straight) with another copper Ethernet port, enable the medium dependent independent crossover (MDIX) parameter for the local port. By default, this parameter is enabled.
BEFORE YOU BEGIN
MDIX must be enabled for the remote port.
DETAILED STEPS
To enable or disable an MDIX connection, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
The Basic Settings section shows the basic parameters.
Step 4
Step 5
Configuring the Debounce Timer
You can enable or disable the debounce timer by using the Link Debounce and Debounce Time fields. In the Link Debounce field, you enable or disable the timer. In the Debounce Time field, you specify the time in milliseconds (ms).
Note
DETAILED STEPS
To enable or disable the debounce timer, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
The Basic Settings section shows the basic parameters.
Step 4
Step 5
A time of 0 milliseconds effectively disables the debounce timer. A time of 1 to 5000 milliseconds is used only if you enabled the timer.
Step 6
Configuring the Interface Speed and Duplex Mode
The interface speed and duplex mode are interrelated, so you should configure both of their parameters at the same time.
To see which speeds and duplex modes you can configure together for Ethernet and management interfaces, see Table 2-1.
Note
BEFORE YOU BEGIN
Make sure that the remote port has a speed setting that supports your changes for the local port. If you want to set the local port to use a specific speed, you must set the remote port for the same speed or set the local port to autonegotiate the speed.
DETAILED STEPS
To configure the interface speed and duplex mode, follow these steps:
Step 1
Step 2
The devices with the interface type that you specified appear in the Summary pane.
Step 3
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Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
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Tabs appear for the device information in the Details pane. The Details tab is active but its sections are not expanded.
Step 4
The Basic Settings shows the basic parameters.
Step 5
Step 6
If one of these options is not available, change the interface speed (see the previous step).
Step 7
Configuring the Flow Control
For Ethernet ports that run at 1 Gbps or faster, you can enable or disable the port's ability to send and receive flow-control pause frames. For Ethernet ports that run slower than 1 Gbps, you can enable or disable only the port's ability to receive pause frames.
When enabling flow control for the local port, you either fully enable the local port to send or receive frames regardless of the flow-control setting of the remote port, or you set the local port to use the desired setting used by the remote port. If you enable both the local and remote port for flow control, or set the desired flow control of the other port, or set a combination of those two states, flow control is enabled for those ports.
Note
For information on configuring flow control, refer to Flow Control.
BEFORE YOU BEGIN
Make sure that the remote port has the corresponding setting for the flow control that you need. If you want the local port to send flow-control pause frames, the remote port has a receive parameter set to on or desired. If you want the local port to receive flow-control frames, you must make sure that the remote port has a send parameter set to on or desired. If you do not want to use flow control, you can set the remote port's send and receive parameters to off.
DETAILED STEPS
To configure the interface flow control, follow these steps:
Step 1
The Summary pane lists the devices with Ethernet interfaces.
Step 2
The Details pane shows tabs and an unexpanded Basic Settings area for the port.
Step 3
The Basic Settings area expands to show the basic parameters used for multiple features.
Step 4
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Step 5
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Step 6
Configuring the MTU Size
You can configure the maximum transmission unit (MTU) size for Layer 2 and Layer 3 Ethernet interfaces. For Layer 3 interfaces, you can configure the MTU to be between 576 and 9216 bytes (even values are required). For Layer 2 interfaces, you can configure the MTU to be either the system default MTU (1500 bytes) or the system jumbo MTU size (which has the default size of 9216 bytes).
Note
By default, DCNM configures Layer 3 parameters. If you want to configure Layer 2 parameters, you need to switch the port mode to Layer 2.
You change the port mode by clicking Port Details and Port Mode Settings in the Details pane and then choosing a Layer 2 mode (Access, Trunk, PVLAN Host, or PVLAN Promiscuous).
After changing the port mode to Layer 2, you can return to configuring Layer 3 interfaces by changing the port mode again, by clicking Port Details and Port Mode Settings, and then choosing a Layer 3 mode (Routed).
This section includes the following topics:
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Configuring the Interface MTU Size
For Layer 3 interfaces, you can configure an MTU size that is between 576 and 9216 bytes.
For Layer 2 interfaces, you can configure all Layer 2 interfaces to use either the default MTU size (1500 bytes) or the system jumbo MTU size (default size of 9216 bytes).
If you need to use a different system jumbo MTU size for Layer 2 interfaces, see the "Configuring the System Jumbo MTU Size" section.
DETAILED STEPS
To change an interface MTU size, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
Note
Step 4
The Basic Settings shows the basic parameters.
Step 5
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Step 6
Configuring the System Jumbo MTU Size
You can configure the system jumbo MTU size, which can be used to specify the MTU size for Layer 2 interfaces. You can specify an even number between 1500 and 9216. If you do not configure the system jumbo MTU size, it defaults to 1500 bytes.
DETAILED STEPS
To configure the system jumbo MTU size, follow these steps:
Step 1
The devices for the type that you specified appear in the Summary pane.
Step 2
Tabs appear for the device information in the Details pane. The Details tab is active but its sections are not expanded.
Step 3
Step 4
Step 5
Step 6
Configuring the Bandwidth
You can configure the bandwidth for Ethernet interfaces. The physical level uses an unchangeable bandwidth of 1 GB, but you can configure a value of 1 to 10,000,000 Kb for Level 3 protocols.
DETAILED STEPS
To change the interface bandwidth, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
The Basic Settings section shows the basic parameters.
Step 4
Step 5
Configuring the Throughput Delay
You can configure the interface throughput delay for Ethernet interfaces. The actual delay time does not change, but you can set an informational value between 1 and 16777215, where the value represents the number of tens of microseconds.
For more information on configuring an informational delay value, see the "Throughput Delay" section.
DETAILED STEPS
To change the informational value of the interface throughput delay, follow these steps:
Step 1
The devices with Ethernet interfaces appear in the Summary pane.
Step 2
Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
Step 3
The Basic Settings section shows the basic parameters.
Step 4
For example, for a delay of 10,000 microseconds, type 1000.
Step 5
Shutting Down and Activating the Interface
You can shut down and restart Ethernet or management interfaces. When you shut down interfaces, they become disabled and all monitoring displays show them as being down. This information is communicated to other network servers through all dynamic routing protocols. When the interfaces are shut down, the interface is not included in any routing updates. To activate the interface, you must restart the device.
DETAILED STEPS
To change the administrative status for an interface, follow these steps:
Step 1
Step 2
The devices with the interface type that you specified appear in the Summary pane.
Step 3
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Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
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Tabs appear for the device information in the Details pane. The Details tab is active but its sections are not expanded.
Step 4
The Basic Settings section shows the basic parameters.
Step 5
Step 6
Step 7
Enabling or Disabling CDP
Note
You can enable or disable CDP for Ethernet and management interfaces. This protocol works only when you have it enabled on both interfaces on the same link.
BEFORE YOU BEGIN
Make sure that the remote port also has this protocol enabled.
DETAILED STEPS
To enable or disable CDP for an interface, follow these steps:
Step 1
Step 2
The devices with the interface type that you specified appear in the Summary pane.
Step 3
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Tabs appear for the port information in the Details pane. The Port Details tab is active but its sections are not expanded.
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Tabs appear for the device information in the Details pane. The Details tab is active but its sections are not expanded.
Step 4
The Basic Settings section shows the basic parameters.
Step 5
Note
Step 6
Configuring the UDLD Mode
You can configure normal or aggressive unidirectional link detection (UDLD) modes for Ethernet interfaces on devices configured to run UDLD. Before you can enable a UDLD mode for an interface, you must make sure that UDLD is already enabled on the device that includes the interface. UDLD must also be enabled on the other linked interface and its device.
To use the normal UDLD mode, you must configure one of the ports for normal mode and configure the other port for the normal or aggressive mode. To use the aggressive UDLD mode, you must configure both ports for the aggressive mode.
By default, UDLD is disabled for the 48-port, 10/100/1000 Ethernet module ports but the normal UDLD mode is enabled for the 32-port, 10 gigabit Ethernet module ports.
BEFORE YOU BEGIN
UDLD must be enabled for the other linked port and its device.
DETAILED STEPS
To enable or disable the beacon mode, follow these steps:
Step 1
Step 2
Step 3
Step 4
Step 5
Tabs and unexpanded sections for the port appear in the Details pane.
Step 6
The Basic Settings section shows the basic parameters.
Step 7
Step 8
Field Descriptions
This section describes the fields shown on the Ethernet pane and includes the following:
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Device: Device Details: MTU Settings Section
Table 2-5 Device: Device Details: MTU Settings Section
Jumbo MTU
System jumbo maximum transmission unit (MTU) size in bytes. The range is 1500 to 9216. The default is 1500.
Device: Device Status Tab
Port: Port Details: Basic Settings Section
Port: Port Details: Port Mode Settings Section
Port: Port Details: Advanced Settings Section
Port: Port Status Tab
