Command Reference

interface

Use the interface global configuration command to configure an interface type and enter interface configuration mode.
interface type number
interface type slot/port (for the Cisco 7200 series routers, and for the Cisco 7500 series routers
with a Packet over SONET Interface Processor)
interface [type slot/port-adapter/port] [ethernet | serial] (for ports on VIP cards in the
Cisco 7500 series routers)
interface serial slot/port:channel-group (for channelized T1 or E1 on Cisco 7500 series routers)
interface serial number:channel-group (for channelized T1 or E1 on the Cisco 4000 series
routers and the Cisco MC3810)

To configure a subinterface, use this form of the interface global configuration commands:
interface type slot/port-adapter/port.subinterface-number {multipoint | point-to-point}
(for ports on VIP cards in the Cisco 7500 series routers)
interface type slot/port.subinterface-number {multipoint | point-to-point} (for the Cisco 7200
series routers)
interface type slot/port-adapter.subinterface-number {multipoint | point-to-point} (for the
Cisco 7500 series)

Syntax Description

type

Type of interface to be configured. See the table of interface type keywords below.

number

Port, connector, or interface card number. On a Cisco 4000 series router, specifies the NPM number. The numbers are assigned at the factory at the time of installation or when added to a system, and can be displayed with the show interfaces command.

slot

Refer to the appropriate hardware manual for slot and port information.

port

Refer to the appropriate hardware manual for slot and port information.

port-adapter

Refer to the appropriate hardware manual for information about port adapter compatibility.

:channel-group

The Cisco 4000 series routers specifies the T1 channel group number in the range of 0 to 23 defined with the channel-group controller configuration command. On a dual port card, it is possible to run channelized on one port and primary rate on the other port.

The Cisco MC3810 specifies the T1/E1 channel group number in the range of 0 to 23 defined with the channel-group controller configuration command.

.subinterface-number

Subinterface number in the range 1 to 4294967293. The number that precedes the period (.) must match the number to which this subinterface belongs.

multipoint | point-to-point

(Optional) Specifies a multipoint or point-to-point subinterface. There is no default.

Default

No interface types are configured.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0 for the Cisco 7000 series routers.
This command first appeared in Cisco IOS Release 11.0 for the Cisco 4000 series routers.

This command was changed in Cisco IOS Release 11.2 to add the posi keyword.
This command was changed in Cisco IOS Release 11.3 to change the posi keyword to pos.
This command was changed in Cisco IOS Release 12.0 to add the switch keyword.

Subinterfaces can be configured to support partially meshed Frame Relay networks. Refer to the part entitled "Configuring Serial Interfaces" in the Cisco IOS Interface Configuration Guide.

There is no correlation between the number of the physical serial interface and the number of the logical LAN Extender interface. These interfaces can have the same or different numbers.

Interface Type Keywords
Keyword Interface Type

async

Port line used as an asynchronous interface.

atm

ATM interface.

bri

Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI). This interface configuration is propagated to each of the B channels. B channels cannot be individually configured. The interface must be configured with dial-on-demand commands in order for calls to be placed on that interface.

dialer

Dialer interface.

ethernet

Ethernet IEEE 802.3 interface.

fastethernet

100-Mbps Ethernet interface on the Cisco 4500, Cisco 4700, Cisco 7000 and Cisco 7500 series routers.

fddi

Fiber Distributed Data Interface (FDDI).

group-async

Master asynchronous interface.

hssi

High-Speed Serial Interface (HSSI).

lex

LAN Extender (LEX) interface.

loopback

Software-only loopback interface that emulates an interface that is always up. It is a virtual interface supported on all platforms. The interface-number is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces you can create.

null

Null interface.

port-channel

Port channel interface

pos

Packet OC-3 interface on the Packet over SONET Interface Processor

serial

Serial interface.

switch

Switch interface

tokenring

Token Ring interface.

tunnel

Tunnel interface; a virtual interface. The number is the number of the tunnel interface that you want to create or configure. There is no limit on the number of tunnel interfaces you can create.

vg-anylan

100VG-AnyLAN port adapter

Examples

The following example configures serial interface 0 with PPP encapsulation:
interface serial 0

  encapsulation ppp
  
The following example enables loopback mode and assigns an IP network address and network mask to the interface. The loopback interface established here will always appear to be up:
interface loopback 0

  ip address 131.108.1.1 255.255.255.0
  
The following example for the Cisco 7500 series router shows the interface configuration command for Ethernet port 4 on the EIP that is installed in (or recently removed from) slot 2:
interface ethernet 2/4
The following example begins configuration on the Token Ring interface processor in slot 1 on
port 0 of a Cisco 7500 series routers:
interface tokenring 1/0
The following example shows how a partially meshed Frame Relay network can be configured. In this example, subinterface serial 0.1 is configured as a multipoint subinterface with three Frame Relay PVCs associated, and subinterface serial 0.2 is configured as a point-to-point subinterface.
interface serial 0
  encapsulation frame-relay
interface serial 0.1 multipoint
  ip address 131.108.10.1 255.255.255.0
  frame-relay interface-dlci 42 broadcast
  frame-relay interface-dlci 53 broadcast
interface serial 0.2 point-to-point
  ip address 131.108.11.1 255.255.0
  frame-relay interface-dlci 59 broadcast
  
The following example configures circuit 0 of a T1 link for Point-to-Point Protocol (PPP) encapsulation:
controller t1 4/1
circuit 0 1
interface serial 4/1:0
  ip address 131.108.13.1 255.255.255.0
  encapsulation ppp
  
The following example configures LAN Extender interface 0:
interface lex 0

type	Type of interface to be configured. See the table of interface type keywords below.
number	Port, connector, or interface card number. On a Cisco 4000 series router, specifies the NPM number. The numbers are assigned at the factory at the time of installation or when added to a system, and can be displayed with the show interfaces command.
slot	Refer to the appropriate hardware manual for slot and port information.
port	Refer to the appropriate hardware manual for slot and port information.
port-adapter	Refer to the appropriate hardware manual for information about port adapter compatibility.
:channel-group	The Cisco 4000 series routers specifies the T1 channel group number in the range of 0 to 23 defined with the channel-group controller configuration command. On a dual port card, it is possible to run channelized on one port and primary rate on the other port. The Cisco MC3810 specifies the T1/E1 channel group number in the range of 0 to 23 defined with the channel-group controller configuration command.
.subinterface-number	Subinterface number in the range 1 to 4294967293. The number that precedes the period (.) must match the number to which this subinterface belongs.
multipoint \| point-to-point	(Optional) Specifies a multipoint or point-to-point subinterface. There is no default.

Keyword	Interface Type
async	Port line used as an asynchronous interface.
atm	ATM interface.
bri	Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI). This interface configuration is propagated to each of the B channels. B channels cannot be individually configured. The interface must be configured with dial-on-demand commands in order for calls to be placed on that interface.
dialer	Dialer interface.
ethernet	Ethernet IEEE 802.3 interface.
fastethernet	100-Mbps Ethernet interface on the Cisco 4500, Cisco 4700, Cisco 7000 and Cisco 7500 series routers.
fddi	Fiber Distributed Data Interface (FDDI).
group-async	Master asynchronous interface.
hssi	High-Speed Serial Interface (HSSI).
lex	LAN Extender (LEX) interface.
loopback	Software-only loopback interface that emulates an interface that is always up. It is a virtual interface supported on all platforms. The interface-number is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces you can create.
null	Null interface.
port-channel	Port channel interface
pos	Packet OC-3 interface on the Packet over SONET Interface Processor
serial	Serial interface.
switch	Switch interface
tokenring	Token Ring interface.
tunnel	Tunnel interface; a virtual interface. The number is the number of the tunnel interface that you want to create or configure. There is no limit on the number of tunnel interfaces you can create.
vg-anylan	100VG-AnyLAN port adapter