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zebra is an IP routing manager. It provides kernel routing table updates, interface lookups, and redistribution of routes between different routing protocols.

Invoking zebra

Besides the common invocation options (:ref:`common-invocation-options`), the zebra specific invocation options are listed below.

.. program:: zebra

.. option:: -b, --batch

   Runs in batch mode. *zebra* parses configuration file and terminates

.. option:: -k, --keep_kernel

   When zebra starts up, don't delete old self inserted routes.

.. option:: -r, --retain

   When program terminates, do not flush routes installed by *zebra* from the

.. option:: -e X, --ecmp X

   Run zebra with a limited ecmp ability compared to what it is compiled to.
   If you are running zebra on hardware limited functionality you can
   force zebra to limit the maximum ecmp allowed to X.  This number
   is bounded by what you compiled FRR with as the maximum number.

.. option:: -n, --vrfwnetns

   When *Zebra* starts with this option, the VRF backend is based on Linux
   network namespaces. That implies that all network namespaces discovered by
   ZEBRA will create an associated VRF. The other daemons will operate on the VRF
   VRF defined by *Zebra*, as usual.

   .. seealso:: :ref:`zebra-vrf`

.. option:: -o, --vrfdefaultname

   When *Zebra* starts with this option, the default VRF name is changed to the

   .. seealso:: :ref:`zebra-vrf`

.. option:: --v6-rr-semantics

   The linux kernel is receiving the ability to use the same route
   replacement semantics for v6 that v4 uses.  If you are using a
   kernel that supports this functionality then run *Zebra* with this
   option and we will use Route Replace Semantics instead of delete
   than add.

Configuration Addresses behaviour

At startup, Zebra will first discover the underlying networking objects from the operating system. This includes interfaces, addresses of interfaces, static routes, etc. Then, it will read the configuration file, including its own interface addresses, static routes, etc. All this information comprises the operational context from Zebra. But configuration context from Zebra will remain the same as the one from :file:`zebra.conf` config file. As an example, executing the following :clicmd:`show running-config` will reflect what was in :file:`zebra.conf`. In a similar way, networking objects that are configured outside of the Zebra like iproute2 will not impact the configuration context from Zebra. This behaviour permits you to continue saving your own config file, and decide what is really to be pushed on the config file, and what is dependent on the underlying system. Note that inversely, from Zebra, you will not be able to delete networking objects that were previously configured outside of Zebra.

Interface Commands

Standard Commands

.. index:: interface IFNAME

.. clicmd:: interface IFNAME

.. index:: interface IFNAME vrf VRF

.. clicmd:: interface IFNAME vrf VRF

.. index:: shutdown

.. clicmd:: shutdown
.. index:: no shutdown

.. clicmd:: no shutdown

   Up or down the current interface.

.. index:: ip address ADDRESS/PREFIX

.. clicmd:: ip address ADDRESS/PREFIX
.. index:: ipv6 address ADDRESS/PREFIX

.. clicmd:: ipv6 address ADDRESS/PREFIX
.. index:: no ip address ADDRESS/PREFIX

.. clicmd:: no ip address ADDRESS/PREFIX
.. index:: no ipv6 address ADDRESS/PREFIX

.. clicmd:: no ipv6 address ADDRESS/PREFIX

   Set the IPv4 or IPv6 address/prefix for the interface.

.. index:: ip address LOCAL-ADDR peer PEER-ADDR/PREFIX

.. clicmd:: ip address LOCAL-ADDR peer PEER-ADDR/PREFIX
.. index:: no ip address LOCAL-ADDR peer PEER-ADDR/PREFIX

.. clicmd:: no ip address LOCAL-ADDR peer PEER-ADDR/PREFIX

   Configure an IPv4 Point-to-Point address on the interface. (The concept of
   PtP addressing does not exist for IPv6.)

   `local-addr` has no subnet mask since the local side in PtP addressing is
   always a single (/32) address. `peer-addr/prefix` can be an arbitrary subnet
   behind the other end of the link (or even on the link in Point-to-Multipoint
   setups), though generally /32s are used.

.. index:: description DESCRIPTION ...

.. clicmd:: description DESCRIPTION ...

   Set description for the interface.

.. index:: multicast

.. clicmd:: multicast
.. index:: no multicast

.. clicmd:: no multicast

   Enable or disables multicast flag for the interface.

.. index:: bandwidth (1-10000000)

.. clicmd:: bandwidth (1-10000000)
.. index:: no bandwidth (1-10000000)

.. clicmd:: no bandwidth (1-10000000)

   Set bandwidth value of the interface in kilobits/sec. This is for
   calculating OSPF cost. This command does not affect the actual device

.. index:: link-detect

.. clicmd:: link-detect
.. index:: no link-detect

.. clicmd:: no link-detect

   Enable/disable link-detect on platforms which support this. Currently only
   Linux and Solaris, and only where network interface drivers support
   reporting link-state via the ``IFF_RUNNING`` flag.

   In FRR, link-detect is on by default.

Link Parameters Commands

.. index:: link-params
.. clicmd:: link-params

.. index:: no link-param
.. clicmd:: no link-param

   Enter into the link parameters sub node. At least 'enable' must be set to
   activate the link parameters, and consequently Traffic Engineering on this
   interface. MPLS-TE must be enable at the OSPF
   (:ref:`ospf-traffic-engineering`) or ISIS (:ref:`isis-traffic-engineering`)
   router level in complement to this.  Disable link parameters for this

   Under link parameter statement, the following commands set the different TE values:

.. index:: link-params [enable]
.. clicmd:: link-params [enable]

   Enable link parameters for this interface.

.. index:: link-params [metric (0-4294967295)]
.. clicmd:: link-params [metric (0-4294967295)]

.. index:: link-params max-bw BANDWIDTH
.. clicmd:: link-params max-bw BANDWIDTH

.. index:: link-params max-rsv-bw BANDWIDTH
.. clicmd:: link-params max-rsv-bw BANDWIDTH

.. index:: link-params unrsv-bw (0-7) BANDWIDTH
.. clicmd:: link-params unrsv-bw (0-7) BANDWIDTH

.. index:: link-params admin-grp BANDWIDTH
.. clicmd:: link-params admin-grp BANDWIDTH

   These commands specifies the Traffic Engineering parameters of the interface
   in conformity to RFC3630 (OSPF) or RFC5305 (ISIS).  There are respectively
   the TE Metric (different from the OSPF or ISIS metric), Maximum Bandwidth
   (interface speed by default), Maximum Reservable Bandwidth, Unreserved
   Bandwidth for each 0-7 priority and Admin Group (ISIS) or Resource
   Class/Color (OSPF).

   Note that BANDIWDTH is specified in IEEE floating point format and express
   in Bytes/second.

.. index::  link-param delay (0-16777215) [min (0-16777215) | max (0-16777215)]
.. clicmd:: link-param delay (0-16777215) [min (0-16777215) | max (0-16777215)]

.. index::  link-param delay-variation (0-16777215)
.. clicmd:: link-param delay-variation (0-16777215)

.. index::  link-param packet-loss PERCENTAGE
.. clicmd:: link-param packet-loss PERCENTAGE

.. index::  link-param res-bw BANDWIDTH
.. clicmd:: link-param res-bw BANDWIDTH

.. index::  link-param ava-bw BANDWIDTH
.. clicmd:: link-param ava-bw BANDWIDTH

.. index::  link-param use-bw BANDWIDTH
.. clicmd:: link-param use-bw BANDWIDTH

   These command specifies additional Traffic Engineering parameters of the
   interface in conformity to draft-ietf-ospf-te-metrics-extension-05.txt and
   draft-ietf-isis-te-metrics-extension-03.txt. There are respectively the
   delay, jitter, loss, available bandwidth, reservable bandwidth and utilized

   Note that BANDWIDTH is specified in IEEE floating point format and express
   in Bytes/second.  Delays and delay variation are express in micro-second
   (µs). Loss is specified in PERCENTAGE ranging from 0 to 50.331642% by step
   of 0.000003.

.. index:: link-param neighbor <A.B.C.D> as (0-65535)
.. clicmd:: link-param neighbor <A.B.C.D> as (0-65535)

.. index:: link-param no neighbor
.. clicmd:: link-param no neighbor

   Specifies the remote ASBR IP address and Autonomous System (AS) number
   for InterASv2 link in OSPF (RFC5392).  Note that this option is not yet
   supported for ISIS (RFC5316).

.. index:: table TABLENO
.. clicmd:: table TABLENO

   Select the primary kernel routing table to be used. This only works for
   kernels supporting multiple routing tables (like GNU/Linux 2.2.x and later).
   After setting TABLENO with this command, static routes defined after this
   are added to the specified table.

Virtual Routing and Forwarding

FRR supports :abbr:`VRF (Virtual Routing and Forwarding)`. VRF is a way to separate networking contexts on the same machine. Those networking contexts are associated with separate interfaces, thus making it possible to associate one interface with a specific VRF.

VRF can be used, for example, when instantiating per enterprise networking services, without having to instantiate the physical host machine or the routing management daemons for each enterprise. As a result, interfaces are separate for each set of VRF, and routing daemons can have their own context for each VRF.

This conceptual view introduces the Default VRF case. If the user does not configure any specific VRF, then by default, FRR uses the Default VRF.

Configuring VRF networking contexts can be done in various ways on FRR. The VRF interfaces can be configured by entering in interface configuration mode :clicmd:`interface IFNAME vrf VRF`.

A VRF backend mode is chosen when running Zebra.

If no option is chosen, then the Linux VRF implementation as references in will be mapped over the Zebra VRF. The routing table associated to that VRF is a Linux table identifier located in the same Linux network namespace where Zebra started.

If the :option:`-n` option is chosen, then the Linux network namespace will be mapped over the Zebra VRF. That implies that Zebra is able to configure several Linux network namespaces. The routing table associated to that VRF is the whole routing tables located in that namespace. For instance, this mode matches OpenStack Network Namespaces. It matches also OpenFastPath. The default behavior remains Linux VRF which is supported by the Linux kernel community, see

Because of that difference, there are some subtle differences when running some commands in relationship to VRF. Here is an extract of some of those commands:

.. index:: vrf VRF
.. clicmd:: vrf VRF

   This command is available on configuration mode. By default, above command
   permits accessing the VRF configuration mode. This mode is available for
   both VRFs. It is to be noted that *Zebra* does not create Linux VRF.
   The network administrator can however decide to provision this command in
   configuration file to provide more clarity about the intended configuration.

.. index:: netns NAMESPACE
.. clicmd:: netns NAMESPACE

   This command is based on VRF configuration mode. This command is available
   when *Zebra* is run in :option:`-n` mode. This command reflects which *Linux
   network namespace* is to be mapped with *Zebra* VRF. It is to be noted that
   *Zebra* creates and detects added/suppressed VRFs from the Linux environment
   (in fact, those managed with iproute2). The network administrator can however
   decide to provision this command in configuration file to provide more clarity
   about the intended configuration.

.. index:: show ip route vrf VRF
.. clicmd:: show ip route vrf VRF

   The show command permits dumping the routing table associated to the VRF. If
   *Zebra* is launched with default settings, this will be the ``TABLENO`` of
   the VRF configured on the kernel, thanks to information provided in If *Zebra* is
   launched with :option:`-n` option, this will be the default routing table of
   the *Linux network namespace* ``VRF``.

.. index:: show ip route vrf VRF table TABLENO
.. clicmd:: show ip route vrf VRF table TABLENO

   The show command is only available with :option:`-n` option. This command
   will dump the routing table ``TABLENO`` of the *Linux network namespace*

By using the :option:`-n` option, the Linux network namespace will be mapped over the Zebra VRF. One nice feature that is possible by handling Linux network namespace is the ability to name default VRF. At startup, Zebra discovers the available Linux network namespace by parsing folder /var/run/netns. Each file stands for a Linux network namespace, but not all Linux network namespaces are available under that folder. This is the case for default VRF. It is possible to name the default VRF, by creating a file, by executing following commands.

touch /var/run/netns/vrf0
mount --bind /proc/self/ns/net /var/run/netns/vrf0

Above command illustrates what happens when the default VRF is visible under var/run/netns/. Here, the default VRF file is vrf0. At startup, FRR detects the presence of that file. It detects that the file statistics information matches the same file statistics information as /proc/self/ns/net ( through stat() function). As statistics information matches, then vrf0 stands for the new default namespace name. Consequently, the VRF naming Default will be overriden by the new discovered namespace name vrf0.

For those who don't use VRF backend with Linux network namespace, it is possible to statically configure and recompile FRR. It is possible to choose an alternate name for default VRF. Then, the default VRF naming will automatically be updated with the new name. To illustrate, if you want to recompile with global value, use the following command:

./configure --with-defaultvrfname=global

MPLS Commands

You can configure static mpls entries in zebra. Basically, handling MPLS consists of popping, swapping or pushing labels to IP packets.

MPLS Acronyms

:abbr:`LSR (Labeled Switch Router)`
Networking devices handling labels used to forward traffic between and through them.
:abbr:`LER (Labeled Edge Router)`
A Labeled edge router is located at the edge of an MPLS network, generally between an IP network and an MPLS network.

MPLS Push Action

The push action is generally used for LER devices, which want to encapsulate all traffic for a wished destination into an MPLS label. This action is stored in routing entry, and can be configured like a route:

.. index:: [no] ip route NETWORK MASK GATEWAY|INTERFACE label LABEL
.. clicmd:: [no] ip route NETWORK MASK GATEWAY|INTERFACE label LABEL

   NETWORK ans MASK stand for the IP prefix entry to be added as static
   route entry.
   GATEWAY is the gateway IP address to reach, in order to reach the prefix.
   INTERFACE is the interface behind which the prefix is located.
   LABEL is the MPLS label to use to reach the prefix abovementioned.

   You can check that the static entry is stored in the zebra RIB database, by
   looking at the presence of the entry.


      zebra(configure)# ip route label 777
      zebra# show ip route
      Codes: K - kernel route, C - connected, S - static, R - RIP,
      O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
      T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
      F - PBR,
      > - selected route, * - FIB route

      S>* [1/0] via, r2-eth0, label 777, 00:39:42

MPLS Swap and Pop Action

The swap action is generally used for LSR devices, which swap a packet with a label, with an other label. The Pop action is used on LER devices, at the termination of the MPLS traffic; this is used to remove MPLS header.

.. index:: [no] mpls lsp INCOMING_LABEL GATEWAY OUTGOING_LABEL|explicit-null|implicit-null
.. clicmd:: [no] mpls lsp INCOMING_LABEL GATEWAY OUTGOING_LABEL|explicit-null|implicit-null

   INCOMING_LABEL and OUTGOING_LABEL are MPLS labels with values ranging from 16
   to 1048575.
   GATEWAY is the gateway IP address where to send MPLS packet.
   The outgoing label can either be a value or have an explicit-null label header. This
   specific header can be read by IP devices. The incoming label can also be removed; in
   that case the implicit-null keyword is used, and the outgoing packet emitted is an IP
   packet without MPLS header.

You can check that the MPLS actions are stored in the zebra MPLS table, by looking at the presence of the entry.

.. index:: show mpls table
.. clicmd:: show mpls table

zebra(configure)# mpls lsp 18 implicit-null
zebra(configure)# mpls lsp 19 20
zebra(configure)# mpls lsp 21 explicit-null
zebra# show mpls table
Inbound                            Outbound
Label     Type          Nexthop     Label
--------  -------  ---------------  --------
18     Static  implicit-null
19     Static  20
21     Static  IPv4 Explicit Null

Multicast RIB Commands

The Multicast RIB provides a separate table of unicast destinations which is used for Multicast Reverse Path Forwarding decisions. It is used with a multicast source's IP address, hence contains not multicast group addresses but unicast addresses.

This table is fully separate from the default unicast table. However, RPF lookup can include the unicast table.

WARNING: RPF lookup results are non-responsive in this version of FRR, i.e. multicast routing does not actively react to changes in underlying unicast topology!

.. index:: ip multicast rpf-lookup-mode MODE
.. clicmd:: ip multicast rpf-lookup-mode MODE

.. index:: no ip multicast rpf-lookup-mode [MODE]
.. clicmd:: no ip multicast rpf-lookup-mode [MODE]

   MODE sets the method used to perform RPF lookups. Supported modes:

      Performs the lookup on the Unicast RIB. The Multicast RIB is never used.

      Performs the lookup on the Multicast RIB. The Unicast RIB is never used.

      Tries to perform the lookup on the Multicast RIB. If any route is found,
      that route is used. Otherwise, the Unicast RIB is tried.

      Performs a lookup on the Multicast RIB and Unicast RIB each. The result
      with the lower administrative distance is used;  if they're equal, the
      Multicast RIB takes precedence.

      Performs a lookup on the Multicast RIB and Unicast RIB each. The result
      with the longer prefix length is used;  if they're equal, the
      Multicast RIB takes precedence.

      The `mrib-then-urib` setting is the default behavior if nothing is
      configured. If this is the desired behavior, it should be explicitly
      configured to make the configuration immune against possible changes in
      what the default behavior is.


Unreachable routes do not receive special treatment and do not cause fallback to a second lookup.

.. index:: show ip rpf ADDR
.. clicmd:: show ip rpf ADDR

   Performs a Multicast RPF lookup, as configured with ``ip multicast
   rpf-lookup-mode MODE``. ADDR specifies the multicast source address to look


      > show ip rpf
      Routing entry for using Unicast RIB

      Known via "kernel", distance 0, metric 0, best
      *, via eth0

   Indicates that a multicast source lookup for would use an
   Unicast RIB entry for with a gateway of

.. index:: show ip rpf
.. clicmd:: show ip rpf

   Prints the entire Multicast RIB. Note that this is independent of the
   configured RPF lookup mode, the Multicast RIB may be printed yet not
   used at all.

.. index:: ip mroute PREFIX NEXTHOP [DISTANCE]
.. clicmd:: ip mroute PREFIX NEXTHOP [DISTANCE]

.. index:: no ip mroute PREFIX NEXTHOP [DISTANCE]
.. clicmd:: no ip mroute PREFIX NEXTHOP [DISTANCE]

   Adds a static route entry to the Multicast RIB. This performs exactly as the
   ``ip route`` command, except that it inserts the route in the Multicast RIB
   instead of the Unicast RIB.

zebra Route Filtering

Zebra supports :dfn:`prefix-list` s and :ref:`route-map` s to match routes received from other FRR components. The permit/deny facilities provided by these commands can be used to filter which routes zebra will install in the kernel.

.. index:: ip protocol PROTOCOL route-map ROUTEMAP
.. clicmd:: ip protocol PROTOCOL route-map ROUTEMAP

   Apply a route-map filter to routes for the specified protocol. PROTOCOL can
   be **any** or one of

   - system,
   - kernel,
   - connected,
   - static,
   - rip,
   - ripng,
   - ospf,
   - ospf6,
   - isis,
   - bgp,
   - hsls.

.. index:: set src ADDRESS
.. clicmd:: set src ADDRESS

   Within a route-map, set the preferred source address for matching routes
   when installing in the kernel.

The following creates a prefix-list that matches all addresses, a route-map that sets the preferred source address, and applies the route-map to all rip routes.

ip prefix-list ANY permit le 32
route-map RM1 permit 10
     match ip address prefix-list ANY
     set src

ip protocol rip route-map RM1

zebra FIB push interface

Zebra supports a 'FIB push' interface that allows an external component to learn the forwarding information computed by the FRR routing suite. This is a loadable module that needs to be enabled at startup as described in :ref:`loadable-module-support`.

In FRR, the Routing Information Base (RIB) resides inside zebra. Routing protocols communicate their best routes to zebra, and zebra computes the best route across protocols for each prefix. This latter information makes up the Forwarding Information Base (FIB). Zebra feeds the FIB to the kernel, which allows the IP stack in the kernel to forward packets according to the routes computed by FRR. The kernel FIB is updated in an OS-specific way. For example, the Netlink interface is used on Linux, and route sockets are used on FreeBSD.

The FIB push interface aims to provide a cross-platform mechanism to support scenarios where the router has a forwarding path that is distinct from the kernel, commonly a hardware-based fast path. In these cases, the FIB needs to be maintained reliably in the fast path as well. We refer to the component that programs the forwarding plane (directly or indirectly) as the Forwarding Plane Manager or FPM.

The FIB push interface comprises of a TCP connection between zebra and the FPM. The connection is initiated by zebra -- that is, the FPM acts as the TCP server.

.. program:: configure

The relevant zebra code kicks in when zebra is configured with the :option:`--enable-fpm` flag. Zebra periodically attempts to connect to the well-known FPM port. Once the connection is up, zebra starts sending messages containing routes over the socket to the FPM. Zebra sends a complete copy of the forwarding table to the FPM, including routes that it may have picked up from the kernel. The existing interaction of zebra with the kernel remains unchanged -- that is, the kernel continues to receive FIB updates as before.

The encapsulation header for the messages exchanged with the FPM is defined by the file :file:`fpm/fpm.h` in the frr tree. The routes themselves are encoded in Netlink or protobuf format, with Netlink being the default.

Protobuf is one of a number of new serialization formats wherein the message schema is expressed in a purpose-built language. Code for encoding/decoding to/from the wire format is generated from the schema. Protobuf messages can be extended easily while maintaining backward-compatibility with older code. Protobuf has the following advantages over Netlink:

  • Code for serialization/deserialization is generated automatically. This reduces the likelihood of bugs, allows third-party programs to be integrated quickly, and makes it easy to add fields.
  • The message format is not tied to an OS (Linux), and can be evolved independently.

As mentioned before, zebra encodes routes sent to the FPM in Netlink format by default. The format can be controlled via the FPM module's load-time option to zebra, which currently takes the values Netlink and protobuf.

The zebra FPM interface uses replace semantics. That is, if a 'route add' message for a prefix is followed by another 'route add' message, the information in the second message is complete by itself, and replaces the information sent in the first message.

If the connection to the FPM goes down for some reason, zebra sends the FPM a complete copy of the forwarding table(s) when it reconnects.

zebra Terminal Mode Commands

.. index:: show ip route
.. clicmd:: show ip route

   Display current routes which zebra holds in its database.

Router# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
 B - BGP * - FIB route.

C*      lo
C*      eth0
.. index:: show ipv6 route
.. clicmd:: show ipv6 route

.. index:: show interface
.. clicmd:: show interface

.. index:: show ip prefix-list [NAME]
.. clicmd:: show ip prefix-list [NAME]

.. index:: show route-map [NAME]
.. clicmd:: show route-map [NAME]

.. index:: show ip protocol
.. clicmd:: show ip protocol

.. index:: show ipforward
.. clicmd:: show ipforward

   Display whether the host's IP forwarding function is enabled or not.
   Almost any UNIX kernel can be configured with IP forwarding disabled.
   If so, the box can't work as a router.

.. index:: show ipv6forward
.. clicmd:: show ipv6forward

   Display whether the host's IP v6 forwarding is enabled or not.

.. index:: show zebra
.. clicmd:: show zebra

   Display various statistics related to the installation and deletion
   of routes, neighbor updates, and LSP's into the kernel.

.. index:: show zebra fpm stats
.. clicmd:: show zebra fpm stats

   Display statistics related to the zebra code that interacts with the
   optional Forwarding Plane Manager (FPM) component.

.. index:: clear zebra fpm stats
.. clicmd:: clear zebra fpm stats

   Reset statistics related to the zebra code that interacts with the
   optional Forwarding Plane Manager (FPM) component.