ip-rule(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | AUTHOR | COLOPHON

IP-RULE(8)                        Linux                       IP-RULE(8)

NAME         top

       ip-rule - routing policy database management

SYNOPSIS         top

       ip [ OPTIONS ] rule { COMMAND | help }

       ip rule [ list [ SELECTOR ]]

       ip rule { add | del } SELECTOR ACTION

       ip rule { flush | save | restore }

       SELECTOR := [ not ] [ from PREFIX ] [ to PREFIX ] [ tos TOS ] [
               fwmark FWMARK[/MASK] ] [ iif STRING ] [ oif STRING ] [
               pref NUMBER ] [ l3mdev ] [ uidrange NUMBER-NUMBER ] [
               ipproto PROTOCOL ] [ sport [ NUMBER | NUMBER-NUMBER ] ] [
               dport [ NUMBER | NUMBER-NUMBER ] ] [ tun_id TUN_ID ]

       ACTION := [ table TABLE_ID ] [ protocol PROTO ] [ nat ADDRESS ] [
               realms [SRCREALM/]DSTREALM ] [ goto NUMBER ] SUPPRESSOR

       SUPPRESSOR := [ suppress_prefixlength NUMBER ] [ suppress_ifgroup
               GROUP ]

       TABLE_ID := [ local | main | default | NUMBER ]

DESCRIPTION         top

       ip rule manipulates rules in the routing policy database control
       the route selection algorithm.

       Classic routing algorithms used in the Internet make routing
       decisions based only on the destination address of packets (and
       in theory, but not in practice, on the TOS field).

       In some circumstances we want to route packets differently
       depending not only on destination addresses, but also on other
       packet fields: source address, IP protocol, transport protocol
       ports or even packet payload.  This task is called 'policy
       routing'.

       To solve this task, the conventional destination based routing
       table, ordered according to the longest match rule, is replaced
       with a 'routing policy database' (or RPDB), which selects routes
       by executing some set of rules.

       Each policy routing rule consists of a selector and an action
       predicate.  The RPDB is scanned in order of decreasing priority
       (note that lower number means higher priority, see the
       description of PREFERENCE below). The selector of each rule is
       applied to {source address, destination address, incoming
       interface, tos, fwmark} and, if the selector matches the packet,
       the action is performed. The action predicate may return with
       success.  In this case, it will either give a route or failure
       indication and the RPDB lookup is terminated. Otherwise, the RPDB
       program continues with the next rule.

       Semantically, the natural action is to select the nexthop and the
       output device.

       At startup time the kernel configures the default RPDB consisting
       of three rules:

       1.     Priority: 0, Selector: match anything, Action: lookup
              routing table local (ID 255).  The local table is a
              special routing table containing high priority control
              routes for local and broadcast addresses.

       2.     Priority: 32766, Selector: match anything, Action: lookup
              routing table main (ID 254).  The main table is the normal
              routing table containing all non-policy routes. This rule
              may be deleted and/or overridden with other ones by the
              administrator.

       3.     Priority: 32767, Selector: match anything, Action: lookup
              routing table default (ID 253).  The default table is
              empty. It is reserved for some post-processing if no
              previous default rules selected the packet.  This rule may
              also be deleted.

       Each RPDB entry has additional attributes. F.e. each rule has a
       pointer to some routing table. NAT and masquerading rules have an
       attribute to select new IP address to translate/masquerade.
       Besides that, rules have some optional attributes, which routes
       have, namely realms.  These values do not override those
       contained in the routing tables. They are only used if the route
       did not select any attributes.

       The RPDB may contain rules of the following types:

              unicast - the rule prescribes to return the route found in
              the routing table referenced by the rule.

              blackhole - the rule prescribes to silently drop the
              packet.

              unreachable - the rule prescribes to generate a 'Network
              is unreachable' error.

              prohibit - the rule prescribes to generate 'Communication
              is administratively prohibited' error.

              nat - the rule prescribes to translate the source address
              of the IP packet into some other value.

       ip rule add - insert a new rule

       ip rule delete - delete a rule

              type TYPE (default)
                     the type of this rule. The list of valid types was
                     given in the previous subsection.

              from PREFIX
                     select the source prefix to match.

              to PREFIX
                     select the destination prefix to match.

              iif NAME
                     select the incoming device to match. If the
                     interface is loopback, the rule only matches
                     packets originating from this host. This means that
                     you may create separate routing tables for
                     forwarded and local packets and, hence, completely
                     segregate them.

              oif NAME
                     select the outgoing device to match. The outgoing
                     interface is only available for packets originating
                     from local sockets that are bound to a device.

              tos TOS

              dsfield TOS
                     select the TOS value to match.

              fwmark MARK
                     select the fwmark value to match.

              uidrange NUMBER-NUMBER
                     select the uid value to match.

              ipproto PROTOCOL
                     select the ip protocol value to match.

              sport NUMBER | NUMBER-NUMBER
                     select the source port value to match. supports
                     port range.

              dport NUMBER | NUMBER-NUMBER
                     select the destination port value to match.
                     supports port range.

              priority PREFERENCE
                     the priority of this rule.  PREFERENCE is an
                     unsigned integer value, higher number means lower
                     priority, and rules get processed in order of
                     increasing number. Each rule should have an
                     explicitly set unique priority value.  The options
                     preference and order are synonyms with priority.

              table TABLEID
                     the routing table identifier to lookup if the rule
                     selector matches.  It is also possible to use
                     lookup instead of table.

              protocol PROTO
                     the routing protocol who installed the rule in
                     question.  As an example when zebra installs a rule
                     it would get RTPROT_ZEBRA as the installing
                     protocol.

              suppress_prefixlength NUMBER
                     reject routing decisions that have a prefix length
                     of NUMBER or less.

              suppress_ifgroup GROUP
                     reject routing decisions that use a device
                     belonging to the interface group GROUP.

              realms FROM/TO
                     Realms to select if the rule matched and the
                     routing table lookup succeeded. Realm TO is only
                     used if the route did not select any realm.

              nat ADDRESS
                     The base of the IP address block to translate (for
                     source addresses).  The ADDRESS may be either the
                     start of the block of NAT addresses (selected by
                     NAT routes) or a local host address (or even zero).
                     In the last case the router does not translate the
                     packets, but masquerades them to this address.
                     Using map-to instead of nat means the same thing.

                     Warning: Changes to the RPDB made with these
                     commands do not become active immediately. It is
                     assumed that after a script finishes a batch of
                     updates, it flushes the routing cache with ip route
                     flush cache.

       ip rule flush - also dumps all the deleted rules.

              protocol PROTO
                     Select the originating protocol.

       ip rule show - list rules
              This command has no arguments.  The options list or lst
              are synonyms with show.

       ip rule save

              protocol PROTO
                     Select the originating protocol.

       save rules table information to stdout
              This command behaves like ip rule show except that the
              output is raw data suitable for passing to ip rule
              restore.

       ip rule restore
              restore rules table information from stdin
              This command expects to read a data stream as returned
              from ip rule save.  It will attempt to restore the rules
              table information exactly as it was at the time of the
              save. Any rules already in the table are left unchanged,
              and duplicates are not ignored.

SEE ALSO         top

       ip(8)

AUTHOR         top

       Original Manpage by Michail Litvak <mci@owl.openwall.com>

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
       TCP/IP networking and traffic) project.  Information about the
       project can be found at 
       ⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-22.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

iproute2                       20 Dec 2011                    IP-RULE(8)

Pages that refer to this page: ip(8)wg-quick(8)