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 loopback· 7

reset counters interface null 8

shutdown· 8

 

default

Syntax

default

View

Loopback interface view, null interface view

Default level

2: System level

Parameters

None

Description

Use default to restore the default settings of the loopback or null interface.

Examples

# Restore the default settings of interface loopback 0.

<Sysname> system-view

[Sysname] interface loopback 0

[Sysname-loopback0] default

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

description

Syntax

description text

undo description

View

Loopback interface view, null interface view

Default level

2: System level

Parameters

text: Interface description, a string of 1 to 80 characters. The string can include case-sensitive letters, digits, special characters, spaces, and other Unicode characters and symbols.

Description

Use description to set a description for the current interface.

Use undo description to restore the default.

By default, the description of a loopback or null interface is interface name Interface, for example, Loopback1 interface.

An interface description can be a 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 device through remote login software that supports this character type.

Each non-English 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. This may break a Unicode character into two parts and create garbled characters at the end of a line.

Related commands: display interface.

Examples

# Set the description for interface loopback 0 to loopback0.

<Sysname> system-view

[Sysname] interface loopback 0

[Sysname-loopback0] description loopback0

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 the 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 display interface loopback 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 detailed 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 protocol processing : disabled

Physical is Loopback

Last clearing of counters:  Never

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

    Last 300 seconds output:  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)    --

# Display brief information about all loopback interfaces in the 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

Loop0                ADM  Administratively

Table 1 Command output

Field	Description
current state	Physical state (up or administratively down) 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. 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 protocol processing	State of the network layer protocol, which can be disabled or enabled (displayed as Internet Address is X.X.X.X/XX Primary).
Physical is Loopback	The physical type of the interface is loopback.
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 (displayed when the interface supports traffic accounting), 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 (displayed when the interface supports traffic accounting), 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 (displayed when the interface supports traffic accounting).
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 (displayed when the interface supports traffic accounting).
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. To see the primary interface, use the display standby state command in High Availability Command Reference.
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.
Description	Description 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 at 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 the 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 display interface null to display information about the null interface. Since Null 0 interface is the only null interface on a device, this command displays information about Null 0 interface even if you do not specify the 0 keyword.

·     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 detailed information about null interface Null 0.

<Sysname> display 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:  0 bytes/sec, 0 bits/sec, 0 packets/sec

    Last 300 seconds output:  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)    --

For the 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, which can only be 0.

Description

Use interface loopback to create a loopback interface or enter loopback interface view.

Use undo interface loopback to remove a loopback interface.

Related commands: display interface loopback.

Examples

# Create interface loopback 0.

<Sysname> system-view

[Sysname] interface loopback 0

[Sysname-LoopBack0]

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 interface null to enter null interface view.

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

Related commands: display interface null.

Examples

# Enter Null 0 interface view.

<Sysname> system-view

[Sysname] interface null 0

[Sysname-NULL0]

reset counters interface loopback

Syntax

reset counters interface [ loopback [ interface-number ] ]

View

User view

Default level

2: System level

Parameters

interface-number: Number of the loopback interface, which can be the number of any existing loopback interface. With this argument, the command clears statistics on a specified loopback interface.

Description

Use reset counters interface loopback to clear statistics on loopback interfaces.

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

·     If you do not specify the loopback keyword, this command clears the statistics on all interfaces in the system.

·     If you specify the loopback keyword without the interface-number argument, this command clears the statistics on all loopback interfaces.

Examples

# Clear statistics on loopback interface Loopback 0.

<Sysname> reset counters interface loopback 0

reset counters interface null

Syntax

reset counters interface [ null [ 0 ] ]

View

User view

Default level

2: System level

Parameters

0: Number of the null interface, which is fixed at 0.

Description

Use reset counters interface null to clear statistics on the null interface.

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

·     If you do not specify the null keyword, this command clears statistics on all interfaces.

·     If you specify the null keyword, this command clears the statistics on interface Null 0 with or without the 0 keyword, because the device supports only one interface Null 0.

Examples

# Clear statistics on interface Null 0.

<Sysname> reset counters interface null 0

shutdown

Syntax

shutdown

undo shutdown

View

Loopback interface view

Default level

2: System level

Parameters

None

Description

Use shutdown to shut down the current loopback interface.

Use undo shutdown to bring up the current loopback interface.

By default, a loopback interface is up.

Examples

# Shut down loopback interface loopback 0.

<Sysname> system-view

[Sysname] interface loopback 0

[Sysname-Loopback1] shutdown