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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 Configuring the Switch Interfaces
Configuring Switch Interfaces
Note You cannot configure speed or duplex mode on Gigabit Interface Conv erter (GBIC) ports, but for certain
types of GBICs, you can configure speed to not negotiate (nonegotiate) if the GBIC ports are connected
to a device tha t d oes n ot su ppor t a uton egotiat ion.
These sec tions descr ibe how to configure the int erface speed and duplex mode:
•Configuration Gu idelines, page 9-12
•Setting the Interface Speed and Duplex Parameters, page 9-13
Note The CPE Ethernet port sett ings hav e special considerat ions and diff erent default settin gs from the switch
10/100 ports. For this information, see the CPE device considerations in the “CPE Ethernet Links”
section on page 10-5.

Configuration Guidelines

When configur ing an inte rface spee d and duplex mode , note these guideli nes:
•Ether net por ts se t to 100 0 Mb ps s hould a lways b e set to f ull du pl ex.
•Gigabit Ethernet ports that do not match the settings of an attached de vice can lose connecti vity and
do not genera te statisti cs.
•If both end s of the line supp ort aut onegotiation , we highly recomm end the defaul t setting of
autonegotiation.
•When conne ctin g an interfac e to a 100BASE-T device that does not autonegot iate, set th e duplex
mode t o full or half to match the device, and set the speed to auto. Auton egotiati on for the speed
setting selects the correct speed ev en if the attached device does not autonegotiate, but duplex mode
must be explicitly set.
•When co nne ct ing a n inte rface to a Giga bit E the rne t d evice tha t do es no t a utonegot ia te, di sabl e
autonegotiation on the switch and set the duplex and flow control parameters to be compatible with
the remote device.
•100BASE-FX ports opera te only at 10 0 Mbps and in full -duplex mode .
•1000BASE-SX ports ope rat e on ly a t 1 000 M bps an d in f ull -du plex mo de.
•GigaStac k-t o-Gi gaSta c k ca sca de c on nect ion s op er ate in ha lf- dup lex mod e, a nd
GigaStack-to-GigaStack point-to-point connections operate in full-duplex mode.
•When Spanning Tree Protocol (STP) is enabled and a port is reconfigured, the switch can take up to
30 seconds t o check for loops. The por t LED is ambe r while STP reco nfigures.
Caution Changing th e interfac e speed and dupl ex mode configurat ion might shut down and re -enable t he
interface during the reconfiguration.