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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 Configuri ng th e Switch Interfaces Configuring Switch Interfaces
become active. In that scenario, a valid configuration is to install the fiber-optic under Uplink Port 1 by
having an SFP module plugged in, and to install the copper under Uplink Port 2 without the SFP module
plugged i n.
Note By using the media-type auto-select command in Cisco IOS command-line interface (CLI), you can
configure the Catalyst 2950 LRE so that the SFP module port does not take precedence over the
10/100/1000 port. In that scenario, whichever media type establishes a link first will have precedence
over the ot her.
For more information about the media-type auto- select, media-type sfp, and media-type rj45
comm an ds, re fer t o th e Catalyst 2950 Desktop Switch Command Reference.

Configuring Interface Speed and Duplex Mode

The 10/100 Ethernet interfaces on the Catalyst 2950 switch operate in 10 or 100 Mbps and in either full-
or half- dupl ex mode. (Ther e are no 10/100 Eth ernet inter faces on the Catalys t 2950 LRE switch .) The
10/100/10 00 Ethe rn et int erfac es ope rat e i n 10, 1 00, or 1 000 M bps on ly in fu ll- dup lex mod e. I n
full-dupl ex mode, two stat ion s c an se nd and re ceive at the sa m e tim e. Wh en p acket s can flow in both
directio ns s imu ltan eou sly, effective Etherne t ba nd wid th d oub les to 20 M bp s for 10- M bps i nter faces,
to 200 Mbps for Fast Ethernet interfaces, and to 2 Gbps for Gigabit interfaces. Full-duplex
communication is often an effective solution to collisions, which are major constrictions in Ethernet
networks . Normal ly, 10-Mb ps ports oper ate in hal f-duplex mod e, whic h means tha t stations ca n eithe r
receive or send .
On th e Ca tal yst 2950 LR E sw it ch, the co ppe r me dia ( 10/10 0/10 00) of the Gi gabi t i nte rface op erat e i n
10/100 full-duplex or half-duplex mode and 1000 Mbps only in full-duplex mode. The fiber-optic media
of the Gi gab it i nter face only op er ate in 10 00 Mb ps and f ul l-du plex m ode .
Note You ca nno t c onfigure spee d an d d uplex o n the LRE p ort s by nor ma l sp ee d an d d upl ex com ma nds , but
need the special local speed and local duplex commands.
You can configure in terface spe ed on Fast Etherne t (10/100 -Mbps ) and Gigabit Et hernet
(10/100 /1000 -M bps) i nte rface s on th e Ca talyst 2950 sw it ch; you ca nnot configu re spe ed on
100BASE-FX, 1000BASE-SX, an d Gigabit In terface Convert er (GBIC ) mod ule interfaces. You can
configure dup lex mode on any Fast Etherne t interfa ces that ar e not set to aut onegotiat e; you can not
configure dup lex mode on 100BASE-FX, 100 0BA SE-SX, an d GBIC- module interface s. The
10/100/ 1000 inter faces can op erate only in full- duplex mode.
Note Th e speed and dup lex comm ands are me ant for cop per me dia. The fiber- optic media always ope rate as
1000 Mbps wi th full auto negotiatio n no matter wha t has been settin g for speed and duplex from the
comm and l in e. For exam pl e, you can use the co mm an d-lin e i n terface t o c onfigu re t he spee d to b e 10
Mbps and half-du plex. If the fiber-optic medium is active, then the switch attempts to perf orm auto
negotiation a s 1 000 M bps wi th f ull aut onego tiat ion. If the co pper me dium is ac tive, then th e sw itc h
advertises as 10 Mbps and hal f-duplex.