Cisco CISCO7201 Installation And Configuration Manual page 80

Configuring a Cisco 7201 Router
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 recommend 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
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
page
Debugging
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.
Cisco 7201 Installation and Configuration Guide
3-16
The negotiation auto feature is not supported when using the rj-45 media type and will be
ignored if implementation is attempted. (Autonegotiation is always on in RJ-45 mode.)
A-9.
Chapter 3
"Gigabit Ethernet Flow Control Information" section on
Starting and Configuring the Router
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