# Basic Commands

The following sections discuss commands common to all the routing daemons.

## Config Commands

In a config file, you can write the debugging options, a vty's password, routing daemon configurations, a log file name, and so forth. This information forms the initial command set for a routing beast as it is starting.

Config files are generally found in /etc/frr.

### Config Methods

There are two ways of configuring FRR.

Traditionally each of the daemons had its own config file. The daemon name plus `.conf` was the default config file name. For example, zebra's default config file was `zebra.conf`. This method is deprecated.

Because of the amount of config files this creates, and the tendency of one daemon to rely on others for certain functionality, most deployments now use "integrated" configuration. In this setup all configuration goes into a single file, typically `/etc/frr/frr.conf`. When starting up FRR using an init script or systemd, `vtysh` is invoked to read the config file and send the appropriate portions to only the daemons interested in them. Running configuration updates are persisted back to this single file using `vtysh`. This is the recommended method. To use this method, add the following line to `/etc/frr/vtysh.conf`:

    service integrated-vtysh-config

If you installed from source or used a package, this is probably already present.

If desired, you can specify a config file using the `-f` or `--config_file` options when starting a daemon.

### Basic Config Commands

hostname HOSTNAME

  Set hostname of the router. It is only for current `vtysh`, it will not be saved to any configuration file even with `write file`.

domainname DOMAINNAME

  Set domainname of the router. It is only for current `vtysh`, it will not be saved to any configuration file even with `write file`.

password PASSWORD

  Set password for vty interface. The `no` form of the command deletes the password. If there is no password, a vty won't accept connections.

enable password PASSWORD

  Set enable password. The `no` form of the command deletes the enable password.

service cputime-stats

  Collect CPU usage statistics for individual FRR event handlers and CLI commands. This is enabled by default and can be disabled if the extra overhead causes a noticeable slowdown on your system.

  Disabling these statistics will also make the `service cputime-warning (1-4294967295)` limit non-functional.

service cputime-warning (1-4294967295)

  Warn if the CPU usage of an event handler or CLI command exceeds the specified limit (in milliseconds.) Such warnings are generally indicative of some routine in FRR mistakenly blocking/hogging the processing loop and should be reported as a FRR bug.

  This command has no effect if `service cputime-stats` is disabled.

service walltime-warning (1-4294967295)

  Warn if the total wallclock time spent handling an event or executing a CLI command exceeds the specified limit (in milliseconds.) This includes time spent waiting for I/O or other tasks executing and may produce excessive warnings if the system is overloaded. (This may still be useful to provide an immediate sign that FRR is not operating correctly due to externally caused starvation.)

log trap LEVEL

  These commands are deprecated and are present only for historical compatibility. The log trap command sets the current logging level for all enabled logging destinations, and it sets the default for all future logging commands that do not specify a level. The normal default logging level is debugging. The `no` form of the command resets the default level for future logging commands to debugging, but it does not change the logging level of existing logging destinations.

log stdout LEVEL

  Enable logging output to stdout. If the optional second argument specifying the logging level is not present, the default logging level (typically debugging) will be used. The `no` form of the command disables logging to stdout. The `LEVEL` argument must have one of these values: emergencies, alerts, critical, errors, warnings, notifications, informational, or debugging. Note that the existing code logs its most important messages with severity `errors`.

  Note

  If `systemd` is in use and stdout is connected to systemd, FRR will automatically switch to `journald` extended logging for this target.

  Warning

  FRRouting uses the `writev()` system call to write log messages. This call is supposed to be atomic, but in reality this does not hold for pipes or terminals, only regular files. This means that in rare cases, concurrent log messages from distinct threads may get jumbled in terminal output. Use a log file and `tail -f` if this rare chance is inacceptable to your setup.

log file [FILENAME [LEVEL]]

  If you want to log into a file, please specify `filename` as in this example:

      log file /var/log/frr/bgpd.log informational

  If the optional second argument specifying the logging level is not present, the default logging level (typically debugging, but can be changed using the deprecated `log trap` command) will be used. The `no` form of the command disables logging to a file.

log syslog [LEVEL]

  Enable logging output to syslog. If the optional second argument specifying the logging level is not present, the default logging level (typically debugging, but can be changed using the deprecated `log trap` command) will be used. The `no` form of the command disables logging to syslog.

  Note

  This uses the system's `syslog()` API, which does not support message batching or structured key/value data pairs. If possible, use `log extended EXTLOGNAME` with `destination syslog [supports-rfc5424]` instead of this.

log extended EXTLOGNAME

  Create an extended logging target with the specified name. The name has no further meaning and is only used to identify the target. Multiple targets can be created and deleted with the `no` form.

  Refer to Extended Logging Target for further details and suboptions.

log monitor [LEVEL]

  This command is deprecated and does nothing.

log facility [FACILITY]

  This command changes the facility used in syslog messages. The default facility is `daemon`. The `no` form of the command resets the facility to the default `daemon` facility.

log record-priority

  To include the severity in all messages logged to a file, to stdout, or to a terminal monitor (i.e. anything except syslog), use the `log record-priority` global configuration command. To disable this option, use the `no` form of the command. By default, the severity level is not included in logged messages. Note: some versions of syslogd can be configured to include the facility and level in the messages emitted.

log timestamp precision [(0-6)]

  This command sets the precision of log message timestamps to the given number of digits after the decimal point. Currently, the value must be in the range 0 to 6 (i.e. the maximum precision is microseconds). To restore the default behavior (1-second accuracy), use the `no` form of the command, or set the precision explicitly to 0.

      log timestamp precision 3

  In this example, the precision is set to provide timestamps with millisecond accuracy.

log commands

  This command enables the logging of all commands typed by a user to all enabled log destinations. The note that logging includes full command lines, including passwords. If the daemon startup option --command-log-always is used to start the daemon then this command is turned on by default and cannot be turned off and the [no] form of the command is dissallowed.

log filtered-file [FILENAME [LEVEL]]

  Configure a destination file for filtered logs with the `log filter-text WORD` command.

log filter-text WORD

  This command forces logs to be filtered on a specific string. A log message will only be printed if it matches on one of the filters in the log-filter table. The filter only applies to file logging targets configured with `log filtered-file [FILENAME [LEVEL]]`.

  Note

  Log filters help when you need to turn on debugs that cause significant load on the system (enabling certain debugs can bring FRR to a halt). Log filters prevent this but you should still expect a small performance hit due to filtering each of all those logs.

  Note

  This setting is not saved to `frr.conf` and not shown in `show running-config`. It is intended for ephemeral debugging purposes only.

clear log filter-text

  This command clears all current filters in the log-filter table.

log immediate-mode

  Use unbuffered output for log and debug messages; normally there is some internal buffering.

log unique-id

  Include `[XXXXX-XXXXX]` log message unique identifier in the textual part of log messages. This is enabled by default, but can be disabled with `no log unique-id`. Please make sure the IDs are enabled when including logs for FRR bug reports.

  The unique identifiers are automatically generated based on source code file name, format string (before filling out) and severity. They do not change "randomly", but some cleanup work may cause large chunks of ID changes between releases. The IDs always start with a letter, consist of letters and numbers (and a dash for readability), are case insensitive, and `I`, `L`, `O` & `U` are excluded.

  This option will not affect future logging targets which allow putting the unique identifier in auxiliary metadata outside the log message text content. (No such logging target exists currently, but RFC5424 syslog and systemd's journald both support it.)

debug unique-id XXXXX-XXXXX backtrace

  Print backtraces (call stack) for specific log messages, identified by their unique ID (see above.) Includes source code location and current event handler being executed. On some systems you may need to install a debug symbols package to get proper function names rather than raw code pointers.

  This command can be issued inside and outside configuration mode, and is saved to configuration only if it was given in configuration mode.

  Warning

  Printing backtraces can significantly slow down logging calls and cause log files to quickly balloon in size. Remember to disable backtraces when they're no longer needed.

debug routemap [detail]

  This command turns on debugging of routemaps. When detail is specified more data is provided to the operator about the reasoning about what is going on in the routemap code.

service password-encryption

  Encrypt password.

service advanced-vty

  Enable advanced mode VTY.

service terminal-length (0-512)

  Set system wide line configuration. This configuration command applies to all VTY interfaces.

line vty

  Enter vty configuration mode.

banner motd default

  Set default motd string.

banner motd file FILE

  Set motd string from file. The file must be in directory specified under `--sysconfdir`.

banner motd line LINE

  Set motd string from an input.

exec-timeout MINUTE [SECOND]

  Set VTY connection timeout value. When only one argument is specified it is used for timeout value in minutes. Optional second argument is used for timeout value in seconds. Default timeout value is 10 minutes. When timeout value is zero, it means no timeout.

  Not setting this, or setting the values to 0 0, means a timeout will not be enabled.

access-class ACCESS-LIST

  Restrict vty connections with an access list.

allow-reserved-ranges

  Allow using IPv4 reserved (Class E) IP ranges for daemons. E.g.: setting IPv4 addresses for interfaces or allowing reserved ranges in BGP next-hops.

  If you need multiple FRR instances (or FRR + any other daemon) running in a single router and peering via 127.0.0.0/8, it's also possible to use this knob if turned on.

  Default: off.

### Sample Config File

Below is a sample configuration file for the zebra daemon.

    !
    ! Zebra configuration file
    !
    frr version 6.0
    frr defaults traditional
    !
    hostname Router
    password zebra
    enable password zebra
    !
    log stdout
    !
    !

`!` and `#` are comment characters. If the first character of the word is one of the comment characters then from the rest of the line forward will be ignored as a comment.

    password zebra!password

If a comment character is not the first character of the word, it's a normal character. So in the above example `!` will not be regarded as a comment and the password is set to `zebra!password`.

### Configuration versioning, profiles and upgrade behavior

All frr daemons share a mechanism to specify a configuration profile and version for loading and saving configuration. Specific configuration settings take different default values depending on the selected profile and version.

While the profile can be selected by user configuration and will remain over upgrades, frr will always write configurations using its current version. This means that, after upgrading, a `write file` may write out a slightly different configuration than what was read in.

Since the previous configuration is loaded with its version's defaults, but the new configuration is written with the new defaults, any default that changed between versions will result in an appropriate configuration entry being written out. FRRouting configuration is sticky, staying consistent over upgrades. Changed defaults will only affect new configuration.

Note that the loaded version persists into interactive configuration sessions. Commands executed in an interactive configuration session are no different from configuration loaded at startup. This means that when, say, you configure a new BGP peer, the defaults used for configuration are the ones selected by the last `frr version` command.

Warning

Saving the configuration does not bump the daemons forward to use the new version for their defaults, but restarting them will, since they will then apply the new `frr version` command that was written out. Manually execute the `frr version` command in `show running-config` to avoid this intermediate state.

This is visible in `show running-config`:

    Current configuration:
    !
    ! loaded from 6.0
    frr version 6.1-dev
    frr defaults traditional
    !

If you save and then restart with this configuration, the old defaults will no longer apply. Similarly, you could execute `frr version 6.1-dev`, causing the new defaults to apply and the `loaded from 6.0` comment to disappear.

#### Profiles

frr provides configuration profiles to adapt its default settings to various usage scenarios. Currently, the following profiles are implemented:

- `traditional` - reflects defaults adhering mostly to IETF standards or common practices in wide-area internet routing.

- `datacenter` - reflects a single administrative domain with intradomain links using aggressive timers.

Your distribution/installation may pre-set a profile through the `-F` command line option on all daemons. All daemons must be configured for the same profile. The value specified on the command line is only a pre-set and any `frr defaults` statement in the configuration will take precedence.

Note

The profile must be the same across all daemons. Mismatches may result in undefined behavior.

You can freely switch between profiles without causing any interruption or configuration changes. All settings remain at their previous values, and `show running-configuration` output will have new output listing the previous default values as explicit configuration. New configuration, e.g. adding a BGP peer, will use the new defaults. To apply the new defaults for existing configuration, the previously-invisible old defaults that are now shown must be removed from the configuration.

#### Upgrade practices for interactive configuration

If you configure frr interactively and use the configuration writing functionality to make changes persistent, the following recommendations apply in regards to upgrades:

1. Skipping major versions should generally work but is still inadvisable. To avoid unneeded issue, upgrade one major version at a time and write out the configuration after each update.

2. After installing a new frr version, check the configuration for differences against your old configuration. If any defaults changed that affect your setup, lines may appear or disappear. If a new line appears, it was previously the default (or not supported) and is now necessary to retain previous behavior. If a line disappears, it previously wasn't the default, but now is, so it is no longer necessary.

3. Check the log files for deprecation warnings by using `grep -i deprecat`.

4. After completing each upgrade, save the configuration and either restart frr or execute `frr version <CURRENT>` to ensure defaults of the new version are fully applied.

#### Upgrade practices for autogenerated configuration

When using frr with generated configurations (e.g. Ansible, Puppet, etc.), upgrade considerations differ somewhat:

1. Always write out a `frr version` statement in the configurations you generate. This ensures that defaults are applied consistently.

2. Try to not run more distinct versions of frr than necessary. Each version may need to be checked individually. If running a mix of older and newer installations, use the oldest version for the `frr version` statement.

3. When rolling out upgrades, generate a configuration as usual with the old version identifier and load it. Check for any differences or deprecation warnings. If there are differences in the configuration, propagate these back to the configuration generator to minimize relying on actual default values.

4. After the last installation of an old version is removed, change the configuration generation to a newer `frr version` as appropriate. Perform the same checks as when rolling out upgrades.

## Terminal Mode Commands

write terminal

  Displays the current configuration to the vty interface.

write file

  Write current configuration to configuration file.

configure [terminal]

  Change to configuration mode. This command is the first step to configuration.

terminal length (0-512)

  Set terminal display length to `(0-512)`. If length is 0, no display control is performed.

who

  Show a list of currently connected vty sessions.

list

  List all available commands.

show version

  Show the current version of frr and its build host information.

show logging

  Shows the current configuration of the logging system. This includes the status of all logging destinations.

show log-filter

  Shows the current log filters applied to each daemon.

show memory [DAEMON]

  Show information on how much memory is used for which specific things in frr. Output may vary depending on system capabilities but will generally look something like this:

      frr# show memory
      System allocator statistics:
        Total heap allocated:  1584 KiB
        Holding block headers: 0 bytes
        Used small blocks:     0 bytes
        Used ordinary blocks:  1484 KiB
        Free small blocks:     2096 bytes
        Free ordinary blocks:  100 KiB
        Ordinary blocks:       2
        Small blocks:          60
        Holding blocks:        0
      (see system documentation for 'mallinfo' for meaning)
      --- qmem libfrr ---
      Buffer                        :          3      24                  72
      Buffer data                   :          1    4120                4120
      Host config                   :          3  (variably sized)        72
      Command Tokens                :       3427      72              247160
      Command Token Text            :       2555  (variably sized)     83720
      Command Token Help            :       2555  (variably sized)     61720
      Command Argument              :          2  (variably sized)        48
      Command Argument Name         :        641  (variably sized)     15672
      [...]
      --- qmem Label Manager ---
      --- qmem zebra ---
      ZEBRA VRF                     :          1     912                 920
      Route Entry                   :         11      80                 968
      Static route                  :          1     192                 200
      RIB destination               :          8      48                 448
      RIB table info                :          4      16                  96
      Nexthop tracking object       :          1     200                 200
      Zebra Name Space              :          1     312                 312
      --- qmem Table Manager ---

  To understand system allocator statistics, refer to your system's mallinfo(3) man page.

  Below these statistics, statistics on individual memory allocation types in frr (so-called MTYPEs) is printed:

  - the first column of numbers is the current count of allocations made for the type (the number decreases when items are freed.)

  - the second column is the size of each item. This is only available if allocations on a type are always made with the same size.

  - the third column is the total amount of memory allocated for the particular type, including padding applied by malloc. This means that the number may be larger than the first column multiplied by the second. Overhead incurred by malloc's bookkeeping is not included in this, and the column may be missing if system support is not available.

  When executing this command from `vtysh`, each of the daemons' memory usage is printed sequentially. You can specify the daemon's name to print only its memory usage.

show motd

  Show current motd banner.

show history

  Dump the vtysh cli history.

logmsg LEVEL MESSAGE

  Send a message to all logging destinations that are enabled for messages of the given severity.

find REGEX...

  This command performs a regex search across all defined commands in all modes. As an example, suppose you're in enable mode and can't remember where the command to turn OSPF segment routing on is:

      frr# find segment-routing on
        (ospf)  segment-routing on
        (isis)  segment-routing on

  The CLI mode is displayed next to each command. In this example, `segment-routing on` is under the router ospf mode.

  Similarly, suppose you want a listing of all commands that contain "l2vpn" and "neighbor":

      frr# find l2vpn.*neighbor
        (view)  show [ip] bgp l2vpn evpn neighbors <A.B.C.D|X:X::X:X|WORD> advertised-routes [json]
        (view)  show [ip] bgp l2vpn evpn neighbors <A.B.C.D|X:X::X:X|WORD> routes [json]
        (view)  show [ip] bgp l2vpn evpn rd ASN:NN_OR_IP-ADDRESS:NN neighbors <A.B.C.D|X:X::X:X|WORD> advertised-routes [json]
        (view)  show [ip] bgp l2vpn evpn rd ASN:NN_OR_IP-ADDRESS:NN neighbors <A.B.C.D|X:X::X:X|WORD> routes [json]
        ...

  Note that when entering spaces as part of a regex specification, repeated spaces will be compressed into a single space for matching purposes. This is a consequence of spaces being used to delimit CLI tokens. If you need to match more than one space, use the `\s` escape.

  POSIX Extended Regular Expressions are supported.

show thread cpu [r|w|t|e|x]

  This command displays system run statistics for all the different event types. If no options is specified all different run types are displayed together. Additionally you can ask to look at (r)ead, (w)rite, (t)imer, (e)vent and e(x)ecute thread event types.

show thread poll

  This command displays FRR's poll data. It allows a glimpse into how we are setting each individual fd for the poll command at that point in time.

show thread timers

  This command displays FRR's timer data for timers that will pop in the future.

show yang operational-data XPATH [{format <json|xml>|translate TRANSLATOR|with-config}] DAEMON

  Display the YANG operational data starting from XPATH. The default format is JSON, but can be displayed in XML as well.

  Normally YANG operational data are located inside containers marked as read-only.

  Optionally it is also possible to display configuration leaves in addition to operational data with the option with-config. This option enables the display of configuration leaves with their currently configured value (if the leaf is optional it will only show if it was created or has a default value).

## Common Invocation Options

These options apply to all frr daemons.

-d, --daemon

  Run in daemon mode.

-f, --config_file <file>

  Set configuration file name.

-h, --help

  Display this help and exit.

-i, --pid_file <file>

  Upon startup the process identifier of the daemon is written to a file, typically in `/var/run`. This file can be used by the init system to implement commands such as `.../init.d/zebra status`, `.../init.d/zebra restart` or `.../init.d/zebra stop`.

  The file name is an run-time option rather than a configure-time option so that multiple routing daemons can be run simultaneously. This is useful when using frr to implement a routing looking glass. One machine can be used to collect differing routing views from differing points in the network.

-A, --vty_addr <address>

  Set the VTY local address to bind to. If set, the VTY socket will only be bound to this address.

-P, --vty_port <port>

  Set the VTY TCP port number. If set to 0 then the TCP VTY sockets will not be opened.

-u <user>

  Set the user and group to run as.

-N <namespace>

  Set the namespace that the daemon will run in. A "/<namespace>" will be added to all files that use the statedir. If you have "/var/run/frr" as the default statedir then it will become "/var/run/frr/<namespace>".

-o, --vrfdefaultname <name>

  Set the name used for the Default VRF in CLI commands and YANG models. This option must be the same for all running daemons. By default, the name is "default".

  See also

  Virtual Routing and Forwarding

-v, --version

  Print program version.

--command-log-always

  Cause the daemon to always log commands entered to the specified log file. This also makes the no log commands command dissallowed. Enabling this is suggested if you have need to track what the operator is doing on this router.

--log <stdout|syslog|file:/path/to/log/file>

  When initializing the daemon, setup the log to go to either stdout, syslog or to a file. These values will be displayed as part of a show run. Additionally they can be overridden at runtime if desired via the normal log commands.

--log-level <emergencies|alerts|critical|errors|warnings|notifications|informational|debugging>

  When initializing the daemon, allow the specification of a default log level at startup from one of the specified levels.

--tcli

  Enable the transactional CLI mode.

--limit-fds <number>

  Limit the number of file descriptors that will be used internally by the FRR daemons. By default, the daemons use the system ulimit value.

## Loadable Module Support

FRR supports loading extension modules at startup. Loading, reloading or unloading modules at runtime is not supported (yet). To load a module, use the following command line option at daemon startup:

-M, --module <module:options>

  Load the specified module, optionally passing options to it. If the module name contains a slash (/), it is assumed to be a full pathname to a file to be loaded. If it does not contain a slash, the /usr/lib/frr/modules directory is searched for a module of the given name; first with the daemon name prepended (e.g. `zebra_mod` for `mod`), then without the daemon name prepended.

  This option is available on all daemons, though some daemons may not have any modules available to be loaded.

### The SNMP Module

If SNMP is enabled during compile-time and installed as part of the package, the `snmp` module can be loaded for the Zebra, bgpd, ospfd, ospf6d and ripd daemons.

The module ignores any options passed to it. Refer to SNMP Support for information on its usage.

### The FPM Module

If FPM is enabled during compile-time and installed as part of the package, the `fpm` module can be loaded for the zebra daemon. This provides the Forwarding Plane Manager ("FPM") API.

The module expects its argument to be either `Netlink` or `protobuf`, specifying the encapsulation to use. `Netlink` is the default, and `protobuf` may not be available if the module was built without protobuf support. Refer to zebra FIB push interface for more information.

## Virtual Terminal Interfaces

VTY -- Virtual Terminal [aka TeletYpe] Interface is a command line interface (CLI) for user interaction with the routing daemon.

### VTY Overview

VTY stands for Virtual TeletYpe interface. It means you can connect to the daemon via the telnet protocol.

To enable a VTY interface, you have to setup a VTY password. If there is no VTY password, one cannot connect to the VTY interface at all.

    % telnet localhost 2601
    Trying 127.0.0.1...
    Connected to localhost.
    Escape character is '^]'.

    Hello, this is |PACKAGE_NAME| (version |PACKAGE_VERSION|)
    |COPYRIGHT_STR|

    User Access Verification

    Password: XXXXX
    Router> ?
      enable .  .  .  Turn on privileged commands
      exit   .  .  .  Exit current mode and down to previous mode
      help   .  .  .  Description of the interactive help system
      list   .  .  .  Print command list
      show   .  .  .  Show system inform

      wh. . .  Display who is on a vty
    Router> enable
    Password: XXXXX
    Router# configure terminal
    Router(config)# interface eth0
    Router(config-if)# ip address 10.0.0.1/8
    Router(config-if)# ^Z
    Router#

### VTY Modes

There are three basic VTY modes:

There are commands that may be restricted to specific VTY modes.

#### VTY View Mode

This mode is for read-only access to the CLI. One may exit the mode by leaving the system, or by entering enable mode.

#### VTY Enable Mode

This mode is for read-write access to the CLI. One may exit the mode by leaving the system, or by escaping to view mode.

#### VTY Other Modes

This page is for describing other modes.

### VTY CLI Commands

Commands that you may use at the command-line are described in the following three subsubsections.

#### CLI Movement Commands

These commands are used for moving the CLI cursor. The `C` character means press the Control Key.

`C`-`f` / `LEFT`

  Move forward one character.

`C`-`b` / `RIGHT`

  Move backward one character.

`M`-`f`

  Move forward one word.

`M`-`b`

  Move backward one word.

`C`-`a`

  Move to the beginning of the line.

`C`-`e`

  Move to the end of the line.

#### CLI Editing Commands

These commands are used for editing text on a line. The `C` character means press the Control Key.

`C`-`h` / `DEL`

  Delete the character before point.

`C`-`d`

  Delete the character after point.

`M`-`d`

  Forward kill word.

`C`-`w`

  Backward kill word.

`C`-`k`

  Kill to the end of the line.

`C`-`u`

  Kill line from the beginning, erasing input.

`C`-`t`

  Transpose character.

#### CLI Advanced Commands

There are several additional CLI commands for command line completions, insta-help, and VTY session management.

`C`-`c`

  Interrupt current input and moves to the next line.

`C`-`z`

  End current configuration session and move to top node.

`C`-`n` / `DOWN`

  Move down to next line in the history buffer.

`C`-`p` / `UP`

  Move up to previous line in the history buffer.

`TAB`

  Use command line completion by typing `TAB`.

`?`

  You can use command line help by typing `help` at the beginning of the line. Typing `?` at any point in the line will show possible completions.

#### Pipe Actions

VTY supports optional modifiers at the end of commands that perform postprocessing on command output or modify the action of commands. These do not show up in the `?` or `TAB` suggestion lists.

`... | include REGEX`

  Filters the output of the preceding command, including only lines which match the POSIX Extended Regular Expression `REGEX`. Do not put the regex in quotes.

  Examples:

      frr# show ip bgp sum json | include remoteAs
            "remoteAs":0,
            "remoteAs":455,
            "remoteAs":99,

      frr# show run | include neigh.*[0-9]{2}\.0\.[2-4]\.[0-9]*
       neighbor 10.0.2.106 remote-as 99
       neighbor 10.0.2.107 remote-as 99
       neighbor 10.0.2.108 remote-as 99
       neighbor 10.0.2.109 remote-as 99
       neighbor 10.0.2.110 remote-as 99
       neighbor 10.0.3.111 remote-as 111