This section covers the basics of building, installing and setting up FRR.
The project publishes packages for Red Hat, Centos, Debian and Ubuntu on the GitHub releases. page. External contributors offer packages for many other platforms including *BSD, Alpine, Gentoo, Docker, and others. There is currently no documentation on how to use those but we hope to add it soon.
In addition to traditional packages the project also builds and publishes universal Snap images, available at https://snapcraft.io/frr.
Building FRR from source is the best way to ensure you have the latest features and bug fixes. Details for each supported platform, including dependency package listings, permissions, and other gotchas, are in the developer’s documentation. This section provides a brief overview on the process.
Getting the Source¶
FRR’s source is available on the project GitHub page.
git clone https://github.com/FRRouting/frr.git
When building from Git there are several branches to choose from. The
master branch is the primary development branch. It should be considered
unstable. Each release has its own branch named
is the release version.
In addition, release tarballs are published on the GitHub releases page here.
FRR has an excellent configure script which automatically detects most host configurations. There are several additional configure options to customize the build to include or exclude specific features and dependencies.
First, update the build system. Change into your FRR source directory and issue:
This will install any missing build scripts and update the Autotools configuration. Once this is done you can move on to choosing your configuration options from the list below.
Do not build zebra daemon.
Do not build ripd.
Do not build ripngd.
Do not build ospfd.
Do not build ospf6d.
Do not build bgpd.
Do not build bfdd.
Make bgpd which does not make bgp announcements at all. This feature is good for using bgpd as a BGP announcement listener.
Enable system defaults to work as if in a Data Center. See defaults.h for what is changed by this configure option.
Enable SNMP support. By default, SNMP support is disabled.
Disable support for OSPF-API, an API to interface directly with ospfd. OSPF-API is enabled if –enable-opaque-lsa is set.
Disable building of the example OSPF-API client.
Disable support for OSPF Router Information (RFC4970 & RFC5088) this requires support for Opaque LSAs and Traffic Engineering.
Do not build isisd.
Do not build fabricd.
Enable IS-IS topology generator.
Enable Traffic Engineering Extension for ISIS (RFC5305)
Enable the support of Linux Realms. Convert tag values from 1-255 into a realm value when inserting into the Linux kernel. Then routing policy can be assigned to the realm. See the tc man page.
Disable support IPV6 router advertisement in zebra.
-rdynamicoption to the linker driver. This is in most cases necessary for getting usable backtraces. This option defaults to on if the compiler is detected as gcc, but giving an explicit enable/disable is suggested.
Controls backtrace support for the crash handlers. This is autodetected by default. Using the switch will enforce the requested behaviour, failing with an error if support is requested but not available. On BSD systems, this needs libexecinfo, while on glibc support for this is part of libc itself.
Turn on some options for compiling FRR within a development environment in mind. Specifically turn on -g3 -O0 for compiling options and add inclusion of grammar sandbox.
Turn on some compile options to allow you to run fuzzing tools against the system. This flag is intended as a developer only tool and should not be used for normal operations.
Build without SNMP support.
Build without VTYSH.
Build with FPM module support.
Alpine Linux does not allow non-numeric characters in the version string. With this option, we provide a way to strip out these characters for APK dev package builds.
Compile FRR with up to X way ECMP supported. This number can be from 0-999. For backwards compatability with older configure options when setting X = 0, we will build FRR with 64 way ECMP. This is needed because there are hardcoded arrays that FRR builds towards, so we need to know how big to make these arrays at build time.
Code coverage reports from gcov require adjustments to the C and LD flags. With this option, gcov instrumentation is added to the build and coverage reports are created during execution. The check-coverage make target is also created to ease report uploading to codecov.io. The upload requires the COMMIT (git hash) and TOKEN (codecov upload token) environment variables be set.
Build with configuration rollback support. Requires SQLite3.
Build the ConfD northbound plugin. Look for the libconfd libs and headers in dir.
Build the Sysrepo northbound plugin.
You may specify any combination of the above options to the configure
script. By default, the executables are placed in
and the configuration files in
installation prefix and other directories may be changed using the following
options to the configuration script.
Install architecture-independent files in prefix [/usr/local].
Look for configuration files in dir [prefix/etc]. Note that sample configuration files will be installed here.
Configure zebra to use dir for local state files, such as pid files and unix sockets.
Look for YANG modules in dir [prefix/share/yang]. Note that the FRR YANG modules will be installed here.
Look for libyang plugins in dir [prefix/lib/frr/libyang_plugins]. Note that the FRR libyang plugins will be installed here.
When it’s desired to run FRR without installing it in the system, it’s possible to configure it as follows to look for YANG modules and libyang plugins in the compile directory: .. code-block:: shell
- ./configure –with-libyang-pluginsdir=”pwd/yang/libyang_plugins/.libs”
Additionally, you may configure zebra to drop its elevated privileges shortly after startup and switch to another user. The configure script will automatically try to configure this support. There are three configure options to control the behaviour of FRR daemons.
Switch to user user shortly after startup, and run as user `user in normal operation.
Switch real and effective group to group shortly after startup.
Create Unix Vty sockets (for use with vtysh) with group ownership set to group. This allows one to create a separate group which is restricted to accessing only the vty sockets, hence allowing one to delegate this group to individual users, or to run vtysh setgid to this group.
The default user and group which will be configured is ‘frr’ if no user or
group is specified. Note that this user or group requires write access to the
local state directory (see
--localstatedir) and requires at least
read access, and write access if you wish to allow daemons to write out their
configuration, to the configuration directory (see
On systems which have the ‘libcap’ capabilities manipulation library (currently only Linux), FRR will retain only minimal capabilities required and will only raise these capabilities for brief periods. On systems without libcap, FRR will run as the user specified and only raise its UID to 0 for brief periods.
There are several options available only to GNU/Linux systems. If you use GNU/Linux, make sure that the current kernel configuration is what you want. FRR will run with any kernel configuration but some recommendations do exist.
- Kernel/User Netlink socket. This is a enables an advanced interface between the Linux kernel and zebra (Kernel Interface).
- This makes it possible to receive Netlink routing messages. If you specify this option, zebra can detect routing information updates directly from the kernel (Kernel Interface).
- This option enables IP multicast and should be specified when you use ripd (RIP) or ospfd (OSPFv2) because these protocols use multicast.
Linux sysctl settings and kernel modules¶
There are several kernel parameters that impact overall operation of FRR when
using Linux as a router. Generally these parameters should be set in a
sysctl related configuration file, e.g.,
Ubuntu based systems and a new file
/etc/sysctl.d/90-routing-sysctl.conf on Centos based systems.
Additional kernel modules are also needed to support MPLS forwarding.
- IPv4 and IPv6 forwarding
The following are set to enable IP forwarding in the kernel:
- MPLS forwarding
Basic MPLS kernel support was introduced 4.1, additional capability was introduced in 4.3 and 4.5. For some general information on Linux MPLS support see https://www.netdevconf.org/1.1/proceedings/slides/prabhu-mpls-tutorial.pdf. The following modules should be loaded to support MPLS forwarding, and are generally added to a configuration file such as
# Load MPLS Kernel Modules mpls_router mpls_iptunnel
The following is an example to enable MPLS forwarding in the kernel:
# Enable MPLS Label processing on all interfaces net.mpls.conf.eth0.input=1 net.mpls.conf.eth1.input=1 net.mpls.conf.eth2.input=1 net.mpls.platform_labels=100000
Make sure to add a line equal to
net.mpls.conf.<if>.inputfor each interface ‘<if>’ used with MPLS and to set labels to an appropriate value.
- VRF forwarding
General information on Linux VRF support can be found in https://www.kernel.org/doc/Documentation/networking/vrf.txt. Kernel support for VRFs was introduced in 4.3 and improved upon through 4.13, which is the version most used in FRR testing (as of June 2018). Additional background on using Linux VRFs and kernel specific features can be found in http://schd.ws/hosted_files/ossna2017/fe/vrf-tutorial-oss.pdf.
The following impacts how BGP TCP sockets are managed across VRFs:
With this setting a BGP TCP socket is opened per VRF. This setting ensures that other TCP services, such as SSH, provided for non-VRF purposes are blocked from VRF associated Linux interfaces.
With this setting a single BGP TCP socket is shared across the system. This setting exposes any TCP service running on the system, e.g., SSH, to all VRFs. Generally this setting is not used in environments where VRFs are used to support multiple administrative groups.
Important note as of June 2018, Kernel versions 4.14-4.18 have a known bug where VRF-specific TCP sockets are not properly handled. When running these kernel versions, if unable to establish any VRF BGP adjacencies, either downgrade to 4.13 or set ‘net.ipv4.tcp_l3mdev_accept=1’. The fix for this issue is planned to be included in future kernel versions so upgrading your kernel may also address this issue.
Once you have chosen your configure options, run the configure script and pass the options you chose:
./configure \ --prefix=/usr \ --enable-exampledir=/usr/share/doc/frr/examples/ \ --localstatedir=/var/run/frr \ --sbindir=/usr/lib/frr \ --sysconfdir=/etc/frr \ --enable-pimd \ --enable-watchfrr \ ...
After configuring the software, you are ready to build and install it for your system.
make && sudo make install
If everything finishes successfully, FRR should be installed. You should now skip to the section on Basic Setup.