Adding upstream version 9.1.upstream/9.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1065 insertions, 0 deletions

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+.. _basic-commands:
+
+**************
+Basic Commands
+**************
+
+The following sections discuss commands common to all the routing daemons.
+
+.. _config-commands:
+
+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 |INSTALL_PREFIX_ETC|.
+
+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 :file:`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 :file:`/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
+:file:`/etc/frr/vtysh.conf`:
+
+.. code-block:: frr
+
+   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 :option:`-f` or
+:option:`--config_file` options when starting a daemon.
+
+
+.. _basic-config-commands:
+
+Basic Config Commands
+---------------------
+
+.. clicmd:: 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``.
+
+.. clicmd:: 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``.
+
+.. clicmd:: 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.
+
+.. clicmd:: enable password PASSWORD
+
+   Set enable password. The ``no`` form of the command deletes the enable
+   password.
+
+.. clicmd:: 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
+   :clicmd:`service cputime-warning (1-4294967295)` limit non-functional.
+
+.. clicmd:: 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 :clicmd:`service cputime-stats` is disabled.
+
+.. clicmd:: 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.)
+
+.. clicmd:: 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.
+
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: 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
+      :clicmd:`log extended EXTLOGNAME` with
+      :clicmd:`destination syslog [supports-rfc5424]` instead of this.
+
+.. clicmd:: 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 :ref:`ext-log-target` for further details and suboptions.
+
+.. clicmd:: log monitor [LEVEL]
+
+   This command is deprecated and does nothing.
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: log filtered-file [FILENAME [LEVEL]]
+
+   Configure a destination file for filtered logs with the
+   :clicmd:`log filter-text WORD` command.
+
+.. clicmd:: 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
+   :clicmd:`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
+      :clicmd:`show running-config`.  It is intended for ephemeral debugging
+      purposes only.
+
+.. clicmd:: clear log filter-text
+
+   This command clears all current filters in the log-filter table.
+
+
+.. clicmd:: log immediate-mode
+
+   Use unbuffered output for log and debug messages; normally there is
+   some internal buffering.
+
+.. clicmd:: 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.)
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: service password-encryption
+
+   Encrypt password.
+
+.. clicmd:: service advanced-vty
+
+   Enable advanced mode VTY.
+
+.. clicmd:: service terminal-length (0-512)
+
+   Set system wide line configuration. This configuration command applies to
+   all VTY interfaces.
+
+.. clicmd:: line vty
+
+   Enter vty configuration mode.
+
+.. clicmd:: banner motd default
+
+   Set default motd string.
+
+.. clicmd:: banner motd file FILE
+
+   Set motd string from file. The file must be in directory specified
+   under ``--sysconfdir``.
+
+.. clicmd:: banner motd line LINE
+
+   Set motd string from an input.
+
+.. clicmd:: 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.
+
+.. clicmd:: access-class ACCESS-LIST
+
+   Restrict vty connections with an access list.
+
+.. clicmd:: 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:
+
+Sample Config File
+------------------
+
+Below is a sample configuration file for the zebra daemon.
+
+.. code-block:: frr
+
+   !
+   ! 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.
+
+.. code-block:: frr
+
+   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 |PACKAGE_NAME| 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, |PACKAGE_NAME| 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``:
+
+.. code-block:: frr
+
+   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
+^^^^^^^^
+
+|PACKAGE_NAME| 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 |PACKAGE_NAME| 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 |PACKAGE_NAME| 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
+   |PACKAGE_NAME| or execute ``frr version <CURRENT>`` to ensure defaults of
+   the new version are fully applied.
+
+
+Upgrade practices for autogenerated configuration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When using |PACKAGE_NAME| 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 |PACKAGE_NAME| 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:
+
+Terminal Mode Commands
+======================
+
+.. clicmd:: write terminal
+
+   Displays the current configuration to the vty interface.
+
+.. clicmd:: write file
+
+   Write current configuration to configuration file.
+
+.. clicmd:: configure [terminal]
+
+   Change to configuration mode. This command is the first step to
+   configuration.
+
+.. clicmd:: terminal length (0-512)
+
+   Set terminal display length to ``(0-512)``. If length is 0, no display
+   control is performed.
+
+.. clicmd:: who
+
+   Show a list of currently connected vty sessions.
+
+.. clicmd:: list
+
+   List all available commands.
+
+.. clicmd:: show version
+
+   Show the current version of |PACKAGE_NAME| and its build host information.
+
+.. clicmd:: show logging
+
+   Shows the current configuration of the logging system. This includes the
+   status of all logging destinations.
+
+.. clicmd:: show log-filter
+
+   Shows the current log filters applied to each daemon.
+
+.. clicmd:: show memory [DAEMON]
+
+   Show information on how much memory is used for which specific things in
+   |PACKAGE_NAME|.  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
+   :manpage:`mallinfo(3)` man page.
+
+   Below these statistics, statistics on individual memory allocation types
+   in |PACKAGE_NAME| (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.
+
+.. clicmd:: show motd
+
+   Show current motd banner.
+
+.. clicmd:: show history
+
+   Dump the vtysh cli history.
+
+.. clicmd:: logmsg LEVEL MESSAGE
+
+   Send a message to all logging destinations that are enabled for messages of
+   the given severity.
+
+.. clicmd:: 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,
+   :clicmd:`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.
+
+
+.. _common-show-commands:
+
+.. clicmd:: 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.
+
+.. clicmd:: 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.
+
+.. clicmd:: show thread timers
+
+   This command displays FRR's timer data for timers that will pop in
+   the future.
+
+.. clicmd:: 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:
+
+Common Invocation Options
+=========================
+
+These options apply to all |PACKAGE_NAME| daemons.
+
+
+.. option:: -d, --daemon
+
+   Run in daemon mode.
+
+.. option:: -f, --config_file <file>
+
+   Set configuration file name.
+
+.. option:: -h, --help
+
+   Display this help and exit.
+
+.. option:: -i, --pid_file <file>
+
+   Upon startup the process identifier of the daemon is written to a file,
+   typically in :file:`/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 |PACKAGE_NAME| to implement a routing looking glass. One machine can
+   be used to collect differing routing views from differing points in the
+   network.
+
+.. option:: -A, --vty_addr <address>
+
+   Set the VTY local address to bind to. If set, the VTY socket will only be
+   bound to this address.
+
+.. option:: -P, --vty_port <port>
+
+   Set the VTY TCP port number. If set to 0 then the TCP VTY sockets will not
+   be opened.
+
+.. option:: -u <user>
+
+   Set the user and group to run as.
+
+.. option:: -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>".
+
+.. option:: -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".
+
+   .. seealso:: :ref:`zebra-vrf`
+
+.. option:: -v, --version
+
+   Print program version.
+
+.. option:: --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.
+
+.. option:: --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.
+
+.. option:: --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.
+
+.. option:: --tcli
+
+   Enable the transactional CLI mode.
+
+.. option:: --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:
+
+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:
+
+
+.. option:: -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 |INSTALL_PREFIX_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 :ref:`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 :ref:`zebra-fib-push-interface` for more information.
+
+
+.. _virtual-terminal-interfaces:
+
+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 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:
+
+VTY Modes
+---------
+
+There are three basic VTY modes:
+
+There are commands that may be restricted to specific VTY modes.
+
+.. _vty-view-mode:
+
+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:
+
+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:
+
+VTY Other Modes
+^^^^^^^^^^^^^^^
+
+This page is for describing other modes.
+
+.. _vty-cli-commands:
+
+VTY CLI Commands
+----------------
+
+Commands that you may use at the command-line are described in the following
+three subsubsections.
+
+.. _cli-movement-commands:
+
+CLI Movement Commands
+^^^^^^^^^^^^^^^^^^^^^
+
+These commands are used for moving the CLI cursor. The :kbd:`C` character
+means press the Control Key.
+
+:kbd:`C-f` / :kbd:`LEFT`
+   Move forward one character.
+
+:kbd:`C-b` / :kbd:`RIGHT`
+   Move backward one character.
+
+:kbd:`M-f`
+   Move forward one word.
+
+:kbd:`M-b`
+   Move backward one word.
+
+:kbd:`C-a`
+   Move to the beginning of the line.
+
+:kbd:`C-e`
+   Move to the end of the line.
+
+
+.. _cli-editing-commands:
+
+CLI Editing Commands
+^^^^^^^^^^^^^^^^^^^^
+
+These commands are used for editing text on a line. The :kbd:`C`
+character means press the Control Key.
+
+
+:kbd:`C-h` / :kbd:`DEL`
+   Delete the character before point.
+
+
+:kbd:`C-d`
+   Delete the character after point.
+
+
+:kbd:`M-d`
+   Forward kill word.
+
+
+:kbd:`C-w`
+   Backward kill word.
+
+
+:kbd:`C-k`
+   Kill to the end of the line.
+
+
+:kbd:`C-u`
+   Kill line from the beginning, erasing input.
+
+
+:kbd:`C-t`
+   Transpose character.
+
+
+CLI Advanced Commands
+^^^^^^^^^^^^^^^^^^^^^
+
+There are several additional CLI commands for command line completions,
+insta-help, and VTY session management.
+
+
+:kbd:`C-c`
+   Interrupt current input and moves to the next line.
+
+
+:kbd:`C-z`
+   End current configuration session and move to top node.
+
+
+:kbd:`C-n` / :kbd:`DOWN`
+   Move down to next line in the history buffer.
+
+
+:kbd:`C-p` / :kbd:`UP`
+   Move up to previous line in the history buffer.
+
+
+:kbd:`TAB`
+   Use command line completion by typing :kbd:`TAB`.
+
+
+:kbd:`?`
+   You can use command line help by typing ``help`` at the beginning of the
+   line.  Typing :kbd:`?` 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 :kbd:`?` or :kbd:`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
+