Usage Guidelines
Use the
speed [10 |
100] command for 10/100 ports, the
speedauto [10100 [1000]] c ommand for 10/100/1000 ports, and the
speed [1000 |
nonegotiate] command for Gigabit Ethernet ports.
Cisco 7600 Series Routers
Cisco 7600 series routers cannot automatically negotiate interface speed and duplex mode if either connecting interface is configured to a value other than
auto.
Ethernet Interfaces
If you set the Ethernet interface speed to
auto on a 10/100-Mbps or 10/100/1000-Mbps Ethernet interface, both speed and duplex are autonegotiated.
Gigabit Ethernet Interfaces
The Gigabit Ethernet interfaces are full duplex only. You cannot change the duplex mode on the Gigabit Ethernet interfaces or on a 10/100/1000-Mbps interface that is configured for Gigabit Ethernet.
SPA Interfaces
The
speed command applies to SPA interfaces that are using RJ-45 media. Gigabit Ethernet interfaces using fiber media support 1000-Mbps speed only, and use the
negotiation command to enable and disable autonegotiation.
See also Flow Control in this Usage Guidelines section.
Speed Command Syntax Combinations
The table below lists the supported command options by interface.
Table 1 Supported speed Command Options
Interface Type
|
Supported Syntax
|
Default Setting
|
Usage Guidelines
|
10/100-Mbps module
|
speed
[10 |
100
speed
auto
[10 |
100
|
auto
|
If the speed is set to
auto, you cannot set
duplex.
If the speed is set to
10 or
100, and you do not configure the duplex setting, the duplex is set to
half.
|
10/100/1000-Mbps interface
|
speed
auto [{ 10 100} [ 1000 ]]
|
auto
|
If the speed is set to
auto, you cannot set
duplex.
If the speed is set to
10 or
100, and you do not configure the duplex setting, the duplex is set to
half by default .
If the speed is set to
10100, the interface is not forced to half duplex by default.
|
100-Mbps fiber modules
|
Factory set
|
Not applicable.
|
|
Gigabit Ethernet module
|
speed
[1000 |
nonegotiate
|
Speed is 1000 or negotiation is enabled.
|
Speed, duplex, flow control, and clocking negotiations are enabled.
|
10-Mbps ports
|
Factory set
|
Not applicable.
|
|
Autonegotiation
To enable the autonegotiation capability on an RJ-45 interface, you must set either the
speed command or the
duplex command to
auto. The default configuration is that both commands are set to
auto.
If you need to force an interface port to operate with certain settings and therefore disable autonegotiation, you must be sure that the remote link is configured for compatible link settings for proper transmission. This includes support of flow control on the link.
When you enable link negotiation, the speed, duplex, flow control, and clocking negotiations between two Gigabit Ethernet ports are automatically enabled.
Flow Control
Flow control support is always advertised when autonegotiation is enabled.
Every interface on a 4-Port 10/100 Fast Ethernet SPA supports transmission of pause frames to stop packet flow when the MSC is full. You cannot disable flow control for an interface on the 4-Port 10/100 Fast Ethernet SPA. Therefore, flow control support is not configurable, but it is advertised during autonegotiaton.
If you disable autonegotiation, then you must be sure that the remote device is configured to support flow control because flow control is automatically enabled for all interfaces on the 4-Port 10/100 Fast Ethernet SPA.
Speed Settings
Separate the
speed-list entries with a space.
When manually configuring the interface speed to either 10 or 100 Mbps, the switch prompts you to configure duplex mode on the interface.
The following
speed-listconfigurations are supported:
-
speed
auto
--Negotiate all speeds.
-
speed
auto
10
100
--Negotiate 10 and 100 speeds only.
-
speed
auto
10
100
1000
--Negotiate all speeds.
Speed and Duplex Combinations
The table below describes the interface behavior for various combinations of the
duplex and
speed command settings. The specified
duplex command configured with the specified
speed command produces the resulting system action.
If you decide to configure the interface speed and duplex commands manually, and enter a value other than
speedauto (for example, 10 or 100 Mbps), ensure that you configure the connecting interface speed command to a matching speed but do not use the
auto keyword.
If you specify both a
duplex and
speed setting other than
autoon an RJ-45 interface, then autonegotiation is disabled for the interface.
You cannot set the duplex mode to
half when the port speed is set at 1000 and similarly, you cannot set the port speed to
1000 when the mode is set to half duplex. In addition, if the port speed is set to
auto, the
duplex command is rejected.
 Caution |
Changing the interface speed and duplex mode might shut down and reenable the interface during the reconfiguration.
|
Table 2 Relationship Between duplex and speed Commands
duplex Command
|
speed Command
|
Resulting System Action
|
duplex
auto
|
speed
auto
|
Autonegotiates both speed and duplex mode. The interface advertises capability for the following link settings:
- 10 Mbps and half duplex
- 10 Mbps and full duplex
- 100 Mbps and half duplex
- 100 Mbps and full duplex
- 1000 Mbps and half duplex (Gigabit Ethernet only)
- 1000 Mbps and full duplex (Gigabit Ethernet only)
|
duplex
auto
|
speed
10
orspeed100orspeed1000
|
Autonegotiates the duplex mode. The interface advertises capability for the configured speed with capability for both half-duplex or full-duplex mode.
For example, if the
speed100command is configured with
duplexauto, then the interface advertises the following capability:
- 100 Mbps and half duplex
- 100 Mbps and full duplex
|
duplex
half
orduplexfull
|
speed
auto
|
Autonegotiates the speed. The interface advertises capability for the configured duplex mode with capability for both 10-Mbps or 100-Mbps operation for Fast Ethernet interfaces, and 10-Mbps, 100-Mbps, and 1000-Mbps for Gigabit Ethernet interfaces.
For example, if the
duplexfullcommand is configured with the
speedauto command, then the interface advertises the following capability:
- 10 Mbps and full duplex
- 100 Mbps and full duplex
- 1000 Mbps and full duplex (Gigabit Ethernet interfaces only)
|
duplex
half
|
speed
10
|
Forces 10-Mbps and half-duplex operation, and disables autonegotiation on the interface.
|
duplex
full
|
speed
10
|
Forces 10-Mbps and full-duplex operation, and disables autonegotiation on the interface.
|
duplex
half
|
speed
100
|
Forces 100-Mbps and half-duplex operation, and disables autonegotiation on the interface.
|
duplex
full
|
speed
100
|
Forces 100-Mbps and full-duplex operation, and disables autonegotiation on the interface.
|
duplex
half
|
speed
1000
|
Forces 1000-Mbps and half-duplex operation, and disables autonegotiation on the interface (Gigabit Ethernet only).
|
duplex
full
|
speed
1000
|
Forces 1000-Mbps and full-duplex operation, and disables autonegotiation on the interface (Gigabit Ethernet only).
|