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Configuring the Interface Transmission and Speed Modes
After changing the media type, configure the speed and duplex transmission modes to appropriately match the new interface
characteristics. Changing the speed and duplex of a Cisco 7201 router Gigabit Ethernet interface is done using the speed and
duplex interface commands.
When using the sfp media type, there is also the additional negotiation auto command that is used to enable the IEEE 802.1z
Gigabit Ethernet (1000 Mbps) autonegotiation protocol.
To turn this negotiation auto feature off (it is on by default), issue the interface command
no negotiation auto. This is useful for connecting to other Gigabit Ethernet equipment that does not support IEEE 802.1z
autonegotiation. We recommended that a fixed speed and duplex setting should be used.
When the interface is configured for negotiation auto, the interface advertises all modes of which it is capable. The link only
comes up if the negotiation process succeeds in finding a common mode between the Cisco 7201 SFP media type and its link
partner.
The sfp media type always defaults to 1000-Mbps, full-duplex operation. The only available speed in this mode is 1000 Mbps;
there is no difference whether 1000 or auto is selected. GE 0/0, GE 0/1 and GE 0/2 support half and full duplex mode; GE 0/3
only supports full duplex mode.
Note Copper SFP modules are considered to be SFP media types, not RJ-45 media types. GE 0/2 and GE 0/3 are optical ports,
whether or not a copper SFP module with an RJ-45 connector, or a standard SFP module is installed.
Note The negotiation auto feature is not supported when using the rj-45 media type and will be ignored if implementation
is attempted. (Auto negotiation is always on in RJ-45 mode.)
When an RJ-45 interface is enabled, it advertises all modes of which it is capable. The link only comes up if the negotiation
process succeeds in finding a common mode between the Cisco 7201 RJ-45 media type and its link partner.
If you change from the sfp to the rj-45 media type, you must set speed and duplex after you have executed the media type
command to ensure the interface operates in the correct mode.
For information on flow control, see the Cisco 7201 Installation and Configuration Guide, Appendix A, “Gigabit Ethernet Flow
Control Information” section.
Debug Information
Cisco IOS provides two commands to provide information on your interfaces: show interface GigabitEthernet 0/X (where X is
0, 1, 2, or 3) and show controllers GigabitEthernet 0/X (where X is 0, 1, 2, or 3).
The output of the show interface command is useful for determining the current operating mode of the interface
(speed/duplex/media type) and the current interface statistics.
The output of the show controllers command displays more information specific to the Cisco 7201 router Gigabit Ethernet
interface. For example, it shows the detected link status, speed, and duplex, and also determines the current status of
autonegotiation and the link partners’ abilities (if it is an autonegotiation-capable interface).
The show controllers command also displays the current operating state of the driver and the Ethernet controller hardware. The
show controllers command is a very powerful debugging aid, especially for Cisco engineers should you need help in debugging
a problem. If you have any problems with your Gigabit Ethernet interfaces, you will need to provide this information to Cisco
for analysis.
Table 3 Supported Speed and Duplex Settings
Media Type Speed Duplex
SFP 1000, auto full, half, auto
1
1. GE 0/3 only supports full duplex mode.
RJ-45 10, 100, 1000, auto full, half, auto