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Catalyst2950 Desktop Switch Software Configuration Guide
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Chapter9 Configuring Interface Characteristics
Configuring Layer 2 Interfaces
Configuring Interface Speed and Duplex Mode
Ethernet interfaces on the switch operate in 10, 100, or 1000 Mbps and in either full or half duplex mode.
In full-duplex mode, two stations can send and receive at the same time. When packets ca n flow in both
directions simultaneously, effective Ethernet bandwidth doubles to 20 Mbps for 10-Mbps int erfaces,
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. Normally, 10-Mbps ports operate in half-duplex mode, which means that stations can either
receive or send.
You can configure interface speed on Fast Ethernet (10/100-Mbps) and Gigabit Ethernet
(10/100/1000-Mbps) interfaces; you cannot configure speed on Gigabi t I nte rface Converter (GBI C)
interfaces. You can configure duplex mode on any Fast Ethernet or Gigabit Ethernet interfaces that are
not set to autonegotiate; you cannot configure duplex mode on GBIC interfaces.The 10/100/1000
interfaces can operate only in full duplex mode if the speed is set to 1000 ; they can autonegotiate to half
duplex if the speed is set to 10 or 100 Mbps.
Note You cannot configure speed or duplex mode on Gigabit Interface Converter (GBIC) ports, but for certain
types of GBICs, you can configure speed to not negotiate (nonegotiate) if connected to a device that
does not support autonegotiation.
Table9-1 Default Layer 2 Ethernet Interface Configuration
Feature Default Setting
Operating mode Layer 2
Allowed VLAN range VLANs 1 – 4094 with the enhanced software image installed
or 1 to 1005 with the standard softwar e image insta lled.
Default VLAN (for access ports) VLAN 1.
Native VLAN (for 802.1Q trunks) VLAN 1.
VLAN trunking Switchport mode dy namic de sirable (supports DT P).
Port enable state All ports are enabled.
Port description None defined.
Speed Autonegotiate.
Duplex mode Autonegotiate.
Flow control Flow control is set to off for receive and desired for send for
Gigabit Ethernet ports.
EtherChannel (PAgP) Disabled on all Ethernet ports. See Chapter26, “Configuring
EtherChannels.”
Broadcast, multicast, and unicast
storm control Disabled. See the “Default Storm Control Configuration” section
on page 17-2.
Protected port Disabled. See the “Configuring Protected Ports” section on
page 17-3.
Port security Disabled. See the “Default Port Security Configuration” section
on page 17-6.
Port Fast Disabled.