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7-2
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 7 Configuring Gigabit Ethernet Interfaces
Setting the Speed and Duplex Mode
Setting the Speed and Duplex Mode
The Gigabit Ethernet ports of the Cisco ASR 901 router can run in full or half- duplex mode—100 Mbps
or 1000 Mbps (1 Gbps). The Cisco ASR 901 router has an autonegotiation feature that allows the router
to negotiate the speed and duplex mode with the corresponding interface at the other end of the
connection.
Autonegotiation is the default setting for the speed and transmission mode.
When you configure an interface speed and duplex mode, follow these guidelines:
• If both ends of the line support autonegotiation, use the default autonegotiation settings.
• When autonegotiation is turned on, it autonegotiates both speed and the duplex mode.
• If one interface supports autonegotiation, and the interface at the other end does not, configure the
duplex mode and speed on both interfaces. If you use the autonegotiation setting on the supported
side, the duplex mode setting is set at half-duplex.
• For Giga Ethernet ports with copper cable, autonegotiation should always be enabled for operating
at 1000Mbps speed.
• Auto-negotiation must be enabled for 1000M full duplex Gigabit Ethernet devices; otherwise
behavior is unpredictable.
Note Speed and duplex can be configured only on the following interfaces:
• Copper gigabitethernet interfaces (0/0-3)
• Combo gigabitethernet interface (0/4-7), when the media type is configured as RJ-45
Note In the following procedure, press the Return key after each step unless otherwise noted. At any time,
you can exit the privileged level and return to the user level by entering disable at the Router# prompt.
Step 3
interface gigabitethernet
slot
/
port
Example:
Router(config)# interface
gigabitethernet 0/1
Specifies the port adapter type and the location of the interface to be
configured. The slot is always 0 and the port is the number of the port.
Step 4
cdp enable
Example:
Router(config-if)# cdp enable
Enables Cisco Discovery Protocol on the router, use the cdp enable
command.
Step 5
end
Example:
Router(config-if)# end
Router#
Exits configuration mode.
Command Purpose