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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter11 Configuring Interface Characteristics
Using the Interface Command

Connecting Interfaces

Devices within a single VLAN can communicate directly through any switch. Ports in d ifferent VLANs
cannot exchange data without going through a routing device or routed interface.
With a standard Layer 2 switch, ports in dif fer ent VLANs ha ve to ex change inf ormation thr ough a ro uter .
In the configuration shown in Figure 11-1, when Host A in VLAN 20 sends data to Host B in VLAN 30,
it must go from Host A to the switch, to the router, back to the switch, and then to Host B.
Figure11-1 Connecting VLANs with Layer 2 Switches
Using the Interface Command
To configure a physical interface (port), use the interface global configuration command to enter interface
configuration mode and to specify the interface type, slot, and number.
Type—Fast Ethernet (fastethernet or fa) for 10/100 Ethernet, Gigabit Ethernet (gi gab ite the rnet or
gi), or LRE (longreachethernet or lo)
Slot—The slot number on the switch (always 0 on this switch).
Port number—The interface number on the switch. The port numbers always begin at 1, starting at
the left when facing the front of the switch, for example, fastethernet 0/1, fastethernet 0/2. If there
is more than one interface type (for example, 10/100 por t s an d G igabi t Et hern et por ts ), the po rt
number starts again with the second interface type: gigabitethernet 0/1, gigabitethernet 0/2.
You can identify physical interfaces by physically checking the interface location on the switch. You can
also use the Cisco IOS show privileged EXEC commands to display information about a specific
interface or all the interfaces on the switch. The re ma ind er of t his ch ap t er pr i mari ly provid es phys ica l
interface configuration procedures.
This section describes how to configure all types of interfaces and ho w to c onfi gure a ran ge of interf aces:
Procedures for Configuring Interfaces, page 11-5
Configuring a Range of Interfaces, page 11-5
Configuring and Using Interface-Range Macros, page 11-7
Host A
Switch
Cisco router
VLAN 20
Host B
VLAN 30
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