:abbr:`PBR` is Policy Based Routing. This implementation supports a very simple interface to allow admins to influence routing on their router. At this time you can only match on destination and source prefixes for an incoming interface. At this point in time, this implementation will only work on Linux.
.. program:: pbrd
:abbr:`PBR` supports all the common FRR daemon start options which are documented elsewhere.
Nexthop groups are a way to encapsulate ECMP information together. It's a listing of ECMP nexthops used to forward packets for when a pbr-map is matched.
.. clicmd:: nexthop-group NAME Create a nexthop-group with an associated NAME. This will put you into a sub-mode where you can specify individual nexthops. To exit this mode type exit or end as per normal conventions for leaving a sub-mode.
.. clicmd:: nexthop [A.B.C.D|X:X::X:XX] [interface] [nexthop-vrf NAME] Create a v4 or v6 nexthop. All normal rules for creating nexthops that you are used to are allowed here. The syntax was intentionally kept the same as creating nexthops as you would for static routes.
.. clicmd:: [no] pbr table range (10000-4294966272) (10000-4294966272) Set or unset the range used to assign numeric table ID's to new nexthop-group tables. Existing tables will not be modified to fit in this range, so it is recommended to configure this before adding nexthop groups. .. seealso:: :ref:`pbr-details`
Showing Nexthop Group Information
.. clicmd:: show pbr nexthop-groups [NAME] Display information on a PBR nexthop-group. If ``NAME`` is omitted, all nexthop groups are shown.
PBR maps are a way to group policies that we would like to apply to individual interfaces. These policies when applied are matched against incoming packets. If matched the nexthop-group or nexthop is used to forward the packets to the end destination.
.. clicmd:: pbr-map NAME seq (1-700) Create a pbr-map with NAME and sequence number specified. This command puts you into a new submode for pbr-map specification. To exit this mode type exit or end as per normal conventions for leaving a sub-mode.
.. clicmd:: match src-ip PREFIX When a incoming packet matches the source prefix specified, take the packet and forward according to the nexthops specified. This command accepts both v4 and v6 prefixes. This command is used in conjunction of the :clicmd:`match dst-ip PREFIX` command for matching.
.. clicmd:: match dst-ip PREFIX When a incoming packet matches the destination prefix specified, take the packet and forward according to the nexthops specified. This command accepts both v4 and v6 prefixes. This command is used in conjuction of the :clicmd:`match src-ip PREFIX` command for matching.
.. clicmd:: set nexthop-group NAME Use the nexthop-group NAME as the place to forward packets when the match commands have matched a packet.
.. clicmd:: set nexthop [A.B.C.D|X:X::X:XX] [interface] [nexthop-vrf NAME] Use this individual nexthop as the place to forward packets when the match commands have matched a packet.
After you have specified a PBR map, in order for it to be turned on, you must apply the PBR map to an interface. This policy application to an interface causes the policy to be installed into the kernel.
.. index:: pbr-policy
.. clicmd:: pbr-policy NAME This command is available under interface sub-mode. This turns on the PBR map NAME and allows it to work properly.
Under the covers a PBR map is translated into two separate constructs in the Linux kernel.
.. index:: PBR Rules
The PBR map specified creates a ip rule ... that is inserted into the Linux kernel that points to a table to use for forwarding once the rule matches.
.. index:: PBR Tables
The creation of a nexthop or nexthop-group is translated to a default route in a table with the nexthops specified as the nexthops for the default route.