Loopback and null interface configuration commands 1

default 1

description· 1

display interface loopback· 2

display interface null 5

interface loopback· 6

interface null 7

reset counters interface· 7

shutdown· 8

 

default

Syntax

default

View

Loopback interface view, null interface view

Default level

2: System level

Parameters

None

Description

Use the default command to restore the default settings for the loopback or null interface.

This command might fail to restore the default settings for some commands for reasons such as command dependencies and system restrictions. You can use the display this command in interface view to check for these commands, and perform their undo forms or follow the command reference to individually restore their default settings. If your restoration attempt still fails, follow the error message to resolve the problem.

 

CAUTION: The default command might interrupt ongoing network services. Make sure you are fully aware of the impacts of this command when you perform it on a live network.

 

Examples

# Restore the default settings for interface loopback 1.

<Sysname> system-view

[Sysname] interface LoopBack 1

[Sysname-LoopBack1] default

This command will restore the default settings. Continue? [Y/N]:y

description

Syntax

description text

undo description

View

Loopback interface view, Null 0 interface view

Default level

2: System level

Parameters

text: Description of the interface, a string of 1 to 80 characters. The string can include case-sensitive letters, digits, spaces, special English characters, and Unicode characters and symbols.

 

NOTE: ·       An interface description can be the mixture of English characters and other Unicode characters. The mixed description cannot exceed the specified length. ·       To use a type of Unicode characters or symbols in an interface description, you must install the corresponding Input Method Editor (IME) and log in to the router through remote login software that supports this character type. ·       Each Unicode character or symbol (non-English characters) takes the space of two regular characters. When the length of a description string reaches or exceeds the maximum line width on the terminal software, the software starts a new line, possibly breaking a Unicode character into two parts. As a result, garbled characters may be displayed at the end of a line.

 

Description

Use the description command to set a description for the current interface.

Use the undo description command to restore the default.

By default, the description of an interface is the interface name followed by the word Interface, Loopback1 Interface for example.

Related commands: display interface.

Examples

# Set the description of loopback interface Loopback 1 as loopback1.

<Sysname> system-view

[Sysname] interface LoopBack 1

[Sysname- LoopBack1] description LoopBack1

display interface loopback

Syntax

display interface [ loopback ] [ brief [ down ] ] [ | { begin | exclude | include } regular-expression ]

display interface loopback interface-number [ brief ] [ | { begin | exclude | include } regular-expression ]

View

Any view

Default level

1: Monitor level

Parameters

interface-number: Loopback interface number, which can be the number of any existing Loopback interface. With this argument, this command displays information about a specified loopback interface.

brief: Displays brief interface information. If you do not specify this keyword, this command displays detailed interface information.

down: Displays information about interfaces in DOWN state and the causes. If you do not specify this keyword, this command displays information about interfaces in all states.

|: Filters command output by specifying a regular expression. For more information about regular expressions, see Fundamentals Configuration Guide.

begin: Displays the first line that matches the specified regular expression and all lines that follow.

exclude: Displays all lines that do not match the specified regular expression.

include: Displays all lines that match the specified regular expression.

regular-expression: Specifies a regular expression, a case-sensitive string of 1 to 256 characters.

Description

Use the display interface loopback command to display information about a Loopback interface.

If you do not specify the loopback keyword, this command displays information about all interfaces on the device.

If you specify the loopback keyword without the interface-number argument, this command displays information about all created loopback interfaces.

Related commands: interface loopback.

Examples

# Display information about interface Loopback 0.

<Sysname> display interface LoopBack 0

LoopBack0 current state: UP

Line protocol current state: UP (spoofing)

Description: LoopBack0 Interface

The Maximum Transmit Unit is 1536

Internet Address is 1.1.1.1/32 Primary

Physical is Loopback

 Last clearing of counters:  Never

    Last 300 seconds input rate:  0 bytes/sec, 0 bits/sec, 0 packets/sec

    Last 300 seconds output rate:  0 bytes/sec, 0 bits/sec, 0 packets/sec

    0 packets input, 0 bytes, 0 drops

    0 packets output, 0 bytes, 0 drops

# Display brief information about interface loopback 0.

<Sysname> display interface LoopBack 0 brief

The brief information of interface(s) under route mode:

Link: ADM - administratively down; Stby - standby

Protocol: (s) - spoofing

Interface            Link Protocol Main IP         Description

Loop0                UP   UP(s)    1.1.1.1

# Display brief information about all loopback interfaces in DOWN state.

<Sysname> display interface LoopBack brief down

The brief information of interface(s) under route mode:

Link: ADM - administratively down; Stby - standby

Interface            Link Cause

Loop1                ADM  Administratively

Table 1 Output description

Field	Description
current state	Physical state of the interface.
Line protocol current state	State of the data link layer protocol: UP (spoofing). Spoofing refers to the spoofing attribute of the interface. That is, when the network layer protocol state of the interface is displayed as up, the corresponding link may not exist, or the corresponding link is non-permanent and established on demand.
Description	Description string of the interface.
The Maximum Transmit Unit	Maximum transmission unit (MTU) of the interface.
Internet Address is 1.1.1.1/32 Primary	Network layer address of the interface.
Physical	Physical type of the interface.
Last clearing of counters	Time when statistics on the logical interface were last cleared by using the reset counters interface command. If the statistics of the interface have never been cleared by using the reset counters interface command since the device started, Never is displayed for this field.
Last 300 seconds input:  0 bytes/sec, 0 bits/sec, 0 packets/sec	Average input rate over the last 300 seconds, where: ·       packets/sec indicates the average number of packets received per second. ·       bytes/sec indicates the average number of bytes received per second. ·       bits/sec indicates the average number of bits received per second.
Last 300 seconds output:  0 bytes/sec, 0 bits/sec, 0 packets/sec	Average output rate over the last 300 seconds, where: ·       packets/sec indicates the average number of packets sent per second. ·       bytes/sec indicates the average number of bytes sent per second. ·       bits/sec indicates the average number of bits sent per second.
0 packets input, 0 bytes, 0 drops	Total number and size (in bytes) of the input packets of the interface and the number of the dropped packets.
0 packets output, 0 bytes, 0 drops	Total number and size (in bytes) of the output packets of the interface and the number of the dropped packets.
The brief information of interface(s) under route mode	Brief information about Layer 3 interfaces.
Link: ADM - administratively down; Stby - standby	Link status: ·       ADM—The interface has been administratively shut down. To recover its physical state, perform the undo shutdown command. ·       Stby—The interface is operating as a backup interface.
Protocol: (s) - spoofing	If the network layer protocol state of an interface is shown as UP, but its link is an on-demand link or not present at all, its protocol attribute includes the spoofing flag (an s in parentheses).
Interface	Abbreviated interface name.
Link	Physical link state of the interface: ·       UP—The link is up. ·       ADM—The link has been administratively shut down. To recover its physical state, perform the undo shutdown command.
Protocol	Protocol connection state of the interface, which can be UP, DOWN, or UP(s).
Main IP	The main IP address of the interface.
Cause	The cause of a DOWN physical link. If the port has been shut down with the shutdown command, this field displays Administratively. To restore the physical state of the interface, use the undo shutdown command.

 

display interface null

Syntax

display interface [ null ] [ brief [ down ] ] [ | { begin | exclude | include } regular-expression ]

display interface null 0 [ brief ] [ | { begin | exclude | include } regular-expression ]

View

Any view

Default level

1: Monitor level

Parameters

0: Specifies interface Null 0. The null interface number is fixed to 0.

brief: Displays brief interface information. If you do not specify this keyword, this command displays detailed interface information.

down: Displays information about interfaces in DOWN state and the causes. If you do not specify this keyword, this command displays information about interfaces in all states.

|: Filters command output by specifying a regular expression. For more information about regular expressions, see Fundamentals Configuration Guide.

begin: Displays the first line that matches the specified regular expression and all lines that follow.

exclude: Displays all lines that do not match the specified regular expression.

include: Displays all lines that match the specified regular expression.

regular-expression: Specifies a regular expression, a case-sensitive string of 1 to 256 characters.

Description

Use the display interface null command to display information about the null interface.

If you do not specify the null keyword, this command displays information about all interfaces on the device.

If you specify the null keyword, this command displays information about interface Null 0 with or without the 0 keyword, because the device supports only one interface Null 0.

Related commands: interface null.

Examples

# Display information about null interface Null 0.

NULL0 current state :UP

Line protocol current state :UP (spoofing)

Description :  NULL0 Interface

The Maximum Transmit Unit is 1500

Internet protocol processing : disabled

Physical is NULL DEV

 Last clearing of counters:  Never

    Last 300 seconds input rate:  0 bytes/sec, 0 bits/sec, 0 packets/sec

    Last 300 seconds output rate:  0 bytes/sec, 0 bits/sec, 0 packets/sec

    0 packets input, 0 bytes, 0 drops

    0 packets output, 0 bytes, 0 drops

# Display brief information about interface Null 0.

<Sysname> display interface Null 0 brief

The brief information of interface(s) under route mode:

Link: ADM - administratively down; Stby - standby

Protocol: (s) - spoofing

Interface            Link Protocol Main IP         Description

NULL0                UP   UP(s)    --

The output of the display interface null command is similar to that of the display interface loopback command. For the description of the display interface null command output, see Table 1.

interface loopback

Syntax

interface loopback interface-number

undo interface loopback interface-number

View

System view

Default level

2: System level

Parameters

interface-number: Loopback interface number, ranging from 0 to 1023.

Description

Use the interface loopback command to create a Loopback interface or enter Loopback interface view if the Loopback interface already exists.

Use the undo interface loopback command to remove a Loopback interface.

Related commands: display interface loopback.

Examples

# Create Loopback 5 interface.

<Sysname> system-view

[Sysname] interface LoopBack 5

[Sysname-LoopBack5]

interface null

Syntax

interface null 0

View

System view

Default level

2: System level

Parameters

0: Specifies interface Null 0. The null interface number is fixed to 0.

Description

Use the interface null command to enter null interface view.

The router has only one null interface, interface Null 0. Interface Null 0 is always up. You cannot remove it or shut it down.

Related commands: display interface null.

Examples

# Enter Null 0 interface view.

<Sysname> system-view

[Sysname] interface Null 0

[Sysname-NULL0]

reset counters interface

Syntax

reset counters interface [ interface-type [ interface-number ] ]

View

User view

Default level

2: System level

Parameters

interface-type: Logical interface type.

interface-number: Logical interface number.

Description

Use the reset counters interface command to clear the statistics of a logical interface.

Before collecting traffic statistics within a specific period of time on a logical interface, you must clear the existing statistics.

If no interface type is specified, this command clears the statistics on all interfaces of the router.

If only the interface type is specified, this command clears the statistics on logical interfaces of the specified interface type.

If both the interface type and interface number are specified, this command clears the statistics on the specified logical interface.

Examples

# Clear the statistics on loopback interface Loopback 1.

<Sysname> reset counters interface LoopBack 1

shutdown

Syntax

shutdown

undo shutdown

View

Loopback interface view

Default level

2: System level

Parameters

None

Description

Use the shutdown command to shut down the current Loopback interface.

Use the undo shutdown command to bring up the current Loopback interface.

By default, a loopback interface is up.

Examples

# Shut down Loopback interface Loopback 1.

<Sysname> system-view

[Sysname] interface LoopBack 1

[Sysname-Loopback1] shutdown