Provided by: iproute2_4.3.0-1ubuntu3_i386 bug

NAME

       ip-route - routing table management

SYNOPSIS

       ip [ ip-OPTIONS ] route  { COMMAND | help }

       ip route { list | flush } SELECTOR

       ip route save SELECTOR

       ip route restore

       ip route get ADDRESS [ from ADDRESS iif STRING  ] [ oif STRING ] [ tos
               TOS ]

       ip route { add | del | change | append | replace } ROUTE

       SELECTOR := [ root PREFIX ] [ match PREFIX ] [ exact PREFIX ] [ table
               TABLE_ID ] [ proto RTPROTO ] [ type TYPE ] [ scope SCOPE ]

       ROUTE := NODE_SPEC [ INFO_SPEC ]

       NODE_SPEC := [ TYPE ] PREFIX [ tos TOS ] [ table TABLE_ID ] [ proto
               RTPROTO ] [ scope SCOPE ] [ metric METRIC ]

       INFO_SPEC := NH OPTIONS FLAGS [ nexthop NH ] ...

       NH := [ via [ FAMILY ] ADDRESS ] [ dev STRING ] [ weight NUMBER ]
               NHFLAGS

       FAMILY := [ inet | inet6 | ipx | dnet | mpls | bridge | link ]

       OPTIONS := FLAGS [ mtu NUMBER ] [ advmss NUMBER ] [ as [ to ] ADDRESS ]
               rtt TIME ] [ rttvar TIME ] [ reordering NUMBER ] [ window
               NUMBER ] [ cwnd NUMBER ] [ ssthresh REALM ] [ realms REALM ] [
               rto_min TIME ] [ initcwnd NUMBER ] [ initrwnd NUMBER ] [
               features FEATURES ] [ quickack BOOL ] [ congctl NAME ] pref
               PREF ]

       TYPE := [ unicast | local | broadcast | multicast | throw | unreachable
               | prohibit | blackhole | nat ]

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

       SCOPE := [ host | link | global | NUMBER ]

       NHFLAGS := [ onlink | pervasive ]

       RTPROTO := [ kernel | boot | static | NUMBER ]

       FEATURES := [ ecn | ]

       PREF := [ low | medium | high ]

DESCRIPTION

       ip route is used to manipulate entries in the kernel routing tables.

       Route types:

               unicast - the route entry describes real paths to the
               destinations covered by the route prefix.

               unreachable - these destinations are unreachable. Packets are
               discarded and the ICMP message host unreachable is generated.
               The local senders get an EHOSTUNREACH error.

               blackhole - these destinations are unreachable. Packets are
               discarded silently.  The local senders get an EINVAL error.

               prohibit - these destinations are unreachable. Packets are
               discarded and the ICMP message communication administratively
               prohibited is generated. The local senders get an EACCES error.

               local - the destinations are assigned to this host. The packets
               are looped back and delivered locally.

               broadcast - the destinations are broadcast addresses. The
               packets are sent as link broadcasts.

               throw - a special control route used together with policy
               rules. If such a route is selected, lookup in this table is
               terminated pretending that no route was found. Without policy
               routing it is equivalent to the absence of the route in the
               routing table. The packets are dropped and the ICMP message net
               unreachable is generated. The local senders get an ENETUNREACH
               error.

               nat - a special NAT route. Destinations covered by the prefix
               are considered to be dummy (or external) addresses which
               require translation to real (or internal) ones before
               forwarding. The addresses to translate to are selected with the
               attribute via.  Warning: Route NAT is no longer supported in
               Linux 2.6.

               anycast - not implemented the destinations are anycast
               addresses assigned to this host. They are mainly equivalent to
               local with one difference: such addresses are invalid when used
               as the source address of any packet.

               multicast - a special type used for multicast routing. It is
               not present in normal routing tables.

       Route tables: Linux-2.x can pack routes into several routing tables
       identified by a number in the range from 1 to 2^31 or by name from the
       file /etc/iproute2/rt_tables By default all normal routes are inserted
       into the main table (ID 254) and the kernel only uses this table when
       calculating routes.  Values (0, 253, 254, and 255) are reserved for
       built-in use.

       Actually, one other table always exists, which is invisible but even
       more important. It is the local table (ID 255). This table consists of
       routes for local and broadcast addresses. The kernel maintains this
       table automatically and the administrator usually need not modify it or
       even look at it.

       The multiple routing tables enter the game when policy routing is used.

       ip route add
              add new route

       ip route change
              change route

       ip route replace
              change or add new one

              to TYPE PREFIX (default)
                     the destination prefix of the route. If TYPE is omitted,
                     ip assumes type unicast.  Other values of TYPE are listed
                     above.  PREFIX is an IP or IPv6 address optionally
                     followed by a slash and the prefix length. If the length
                     of the prefix is missing, ip assumes a full-length host
                     route. There is also a special PREFIX default - which is
                     equivalent to IP 0/0 or to IPv6 ::/0.

              tos TOS

              dsfield TOS
                     the Type Of Service (TOS) key. This key has no associated
                     mask and the longest match is understood as: First,
                     compare the TOS of the route and of the packet. If they
                     are not equal, then the packet may still match a route
                     with a zero TOS.  TOS is either an 8 bit hexadecimal
                     number or an identifier from /etc/iproute2/rt_dsfield.

              metric NUMBER

              preference NUMBER
                     the preference value of the route.  NUMBER is an
                     arbitrary 32bit number.

              table TABLEID
                     the table to add this route to.  TABLEID may be a number
                     or a string from the file /etc/iproute2/rt_tables.  If
                     this parameter is omitted, ip assumes the main table,
                     with the exception of local, broadcast and nat routes,
                     which are put into the local table by default.

              dev NAME
                     the output device name.

              via [ FAMILY ] ADDRESS
                     the address of the nexthop router, in the address family
                     FAMILY.  Actually, the sense of this field depends on the
                     route type.  For normal unicast routes it is either the
                     true next hop router or, if it is a direct route
                     installed in BSD compatibility mode, it can be a local
                     address of the interface. For NAT routes it is the first
                     address of the block of translated IP destinations.

              src ADDRESS
                     the source address to prefer when sending to the
                     destinations covered by the route prefix.

              realm REALMID
                     the realm to which this route is assigned.  REALMID may
                     be a number or a string from the file
                     /etc/iproute2/rt_realms.

              mtu MTU

              mtu lock MTU
                     the MTU along the path to the destination. If the
                     modifier lock is not used, the MTU may be updated by the
                     kernel due to Path MTU Discovery. If the modifier lock is
                     used, no path MTU discovery will be tried, all packets
                     will be sent without the DF bit in IPv4 case or
                     fragmented to MTU for IPv6.

              window NUMBER
                     the maximal window for TCP to advertise to these
                     destinations, measured in bytes. It limits maximal data
                     bursts that our TCP peers are allowed to send to us.

              rtt TIME
                     the initial RTT ('Round Trip Time') estimate. If no
                     suffix is specified the units are raw values passed
                     directly to the routing code to maintain compatibility
                     with previous releases.  Otherwise if a suffix of s, sec
                     or secs is used to specify seconds and ms, msec or msecs
                     to specify milliseconds.

              rttvar TIME (2.3.15+ only)
                     the initial RTT variance estimate. Values are specified
                     as with rtt above.

              rto_min TIME (2.6.23+ only)
                     the minimum TCP Retransmission TimeOut to use when
                     communicating with this destination. Values are specified
                     as with rtt above.

              ssthresh NUMBER (2.3.15+ only)
                     an estimate for the initial slow start threshold.

              cwnd NUMBER (2.3.15+ only)
                     the clamp for congestion window. It is ignored if the
                     lock flag is not used.

              initcwnd NUMBER (2.5.70+ only)
                     the initial congestion window size for connections to
                     this destination.  Actual window size is this value
                     multiplied by the MSS (``Maximal Segment Size'') for same
                     connection. The default is zero, meaning to use the
                     values specified in RFC2414.

              initrwnd NUMBER (2.6.33+ only)
                     the initial receive window size for connections to this
                     destination.  Actual window size is this value multiplied
                     by the MSS of the connection.  The default value is zero,
                     meaning to use Slow Start value.

              features FEATURES (3.18+only)
                     Enable or disable per-route features. Only available
                     feature at this time is ecn to enable explicit congestion
                     notification when initiating connections to the given
                     destination network.  When responding to a connection
                     request from the given network, ecn will also be used
                     even if the net.ipv4.tcp_ecn sysctl is set to 0.

              quickack BOOL (3.11+ only)
                     Enable or disable quick ack for connections to this
                     destination.

              congctl NAME (3.20+ only)

              congctl lock NAME (3.20+ only)
                     Sets a specific TCP congestion control algorithm only for
                     a given destination.  If not specified, Linux keeps the
                     current global default TCP congestion control algorithm,
                     or the one set from the application. If the modifier lock
                     is not used, an application may nevertheless overwrite
                     the suggested congestion control algorithm for that
                     destination. If the modifier lock is used, then an
                     application is not allowed to overwrite the specified
                     congestion control algorithm for that destination, thus
                     it will be enforced/guaranteed to use the proposed
                     algorithm.

              advmss NUMBER (2.3.15+ only)
                     the MSS ('Maximal Segment Size') to advertise to these
                     destinations when establishing TCP connections. If it is
                     not given, Linux uses a default value calculated from the
                     first hop device MTU.  (If the path to these destination
                     is asymmetric, this guess may be wrong.)

              reordering NUMBER (2.3.15+ only)
                     Maximal reordering on the path to this destination.  If
                     it is not given, Linux uses the value selected with
                     sysctl variable net/ipv4/tcp_reordering.

              nexthop NEXTHOP
                     the nexthop of a multipath route.  NEXTHOP is a complex
                     value with its own syntax similar to the top level
                     argument lists:

                             via [ FAMILY ] ADDRESS - is the nexthop router.

                             dev NAME - is the output device.

                             weight NUMBER - is a weight for this element of a
                             multipath route reflecting its relative bandwidth
                             or quality.

              scope SCOPE_VAL
                     the scope of the destinations covered by the route
                     prefix.  SCOPE_VAL may be a number or a string from the
                     file /etc/iproute2/rt_scopes.  If this parameter is
                     omitted, ip assumes scope global for all gatewayed
                     unicast routes, scope link for direct unicast and
                     broadcast routes and scope host for local routes.

              protocol RTPROTO
                     the routing protocol identifier of this route.  RTPROTO
                     may be a number or a string from the file
                     /etc/iproute2/rt_protos.  If the routing protocol ID is
                     not given, ip assumes protocol boot (i.e. it assumes the
                     route was added by someone who doesn't understand what
                     they are doing). Several protocol values have a fixed
                     interpretation.  Namely:

                             redirect - the route was installed due to an ICMP
                             redirect.

                             kernel - the route was installed by the kernel
                             during autoconfiguration.

                             boot - the route was installed during the bootup
                             sequence.  If a routing daemon starts, it will
                             purge all of them.

                             static - the route was installed by the
                             administrator to override dynamic routing.
                             Routing daemon will respect them and, probably,
                             even advertise them to its peers.

                             ra - the route was installed by Router Discovery
                             protocol.

                     The rest of the values are not reserved and the
                     administrator is free to assign (or not to assign)
                     protocol tags.

              onlink pretend that the nexthop is directly attached to this
                     link, even if it does not match any interface prefix.

              pref PREF
                     the IPv6 route preference.  PREF is a string specifying
                     the route preference as defined in RFC4191 for Router
                     Discovery messages. Namely:

                             low - the route has a lowest priority

                             medium - the route has a default priority

                             high - the route has a highest priority

       ip route delete
              delete route
              ip route del has the same arguments as ip route add, but their
              semantics are a bit different.

              Key values (to, tos, preference and table) select the route to
              delete. If optional attributes are present, ip verifies that
              they coincide with the attributes of the route to delete.  If no
              route with the given key and attributes was found, ip route del
              fails.

       ip route show
              list routes
              the command displays the contents of the routing tables or the
              route(s) selected by some criteria.

              to SELECTOR (default)
                     only select routes from the given range of destinations.
                     SELECTOR consists of an optional modifier (root, match or
                     exact) and a prefix.  root PREFIX selects routes with
                     prefixes not shorter than PREFIX.  F.e.  root 0/0 selects
                     the entire routing table.  match PREFIX selects routes
                     with prefixes not longer than PREFIX.  F.e.  match
                     10.0/16 selects 10.0/16, 10/8 and 0/0, but it does not
                     select 10.1/16 and 10.0.0/24.  And exact PREFIX (or just
                     PREFIX) selects routes with this exact prefix. If neither
                     of these options are present, ip assumes root 0/0 i.e. it
                     lists the entire table.

              tos TOS

              dsfield TOS
                     only select routes with the given TOS.

              table TABLEID
                     show the routes from this table(s). The default setting
                     is to show table main.  TABLEID may either be the ID of a
                     real table or one of the special values:

                             all - list all of the tables.

                             cache - dump the routing cache.

              cloned

              cached list cloned routes i.e. routes which were dynamically
                     forked from other routes because some route attribute
                     (f.e. MTU) was updated.  Actually, it is equivalent to
                     table cache.

              from SELECTOR
                     the same syntax as for to, but it binds the source
                     address range rather than destinations.  Note that the
                     from option only works with cloned routes.

              protocol RTPROTO
                     only list routes of this protocol.

              scope SCOPE_VAL
                     only list routes with this scope.

              type TYPE
                     only list routes of this type.

              dev NAME
                     only list routes going via this device.

              via [ FAMILY ] PREFIX
                     only list routes going via the nexthop routers selected
                     by PREFIX.

              src PREFIX
                     only list routes with preferred source addresses selected
                     by PREFIX.

              realm REALMID

              realms FROMREALM/TOREALM
                     only list routes with these realms.

       ip route flush
              flush routing tables
              this command flushes routes selected by some criteria.

              The arguments have the same syntax and semantics as the
              arguments of ip route show, but routing tables are not listed
              but purged. The only difference is the default action: show
              dumps all the IP main routing table but flush prints the helper
              page.

              With the -statistics option, the command becomes verbose. It
              prints out the number of deleted routes and the number of rounds
              made to flush the routing table. If the option is given twice,
              ip route flush also dumps all the deleted routes in the format
              described in the previous subsection.

       ip route get
              get a single route
              this command gets a single route to a destination and prints its
              contents exactly as the kernel sees it.

              to ADDRESS (default)
                     the destination address.

              from ADDRESS
                     the source address.

              tos TOS

              dsfield TOS
                     the Type Of Service.

              iif NAME
                     the device from which this packet is expected to arrive.

              oif NAME
                     force the output device on which this packet will be
                     routed.

              connected
                     if no source address (option from) was given, relookup
                     the route with the source set to the preferred address
                     received from the first lookup.  If policy routing is
                     used, it may be a different route.

              Note that this operation is not equivalent to ip route show.
              show shows existing routes.  get resolves them and creates new
              clones if necessary. Essentially, get is equivalent to sending a
              packet along this path.  If the iif argument is not given, the
              kernel creates a route to output packets towards the requested
              destination.  This is equivalent to pinging the destination with
              a subsequent ip route ls cache, however, no packets are actually
              sent. With the iif argument, the kernel pretends that a packet
              arrived from this interface and searches for a path to forward
              the packet.

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

       ip route restore
              restore routing table information from stdin
              This command expects to read a data stream as returned from ip
              route save.  It will attempt to restore the routing table
              information exactly as it was at the time of the save, so any
              translation of information in the stream (such as device
              indexes) must be done first. Any existing routes are left
              unchanged. Any routes specified in the data stream that already
              exist in the table will be ignored.

EXAMPLES

       ip ro
           Show all route entries in the kernel.

       ip route add default via 192.168.1.1 dev eth0
           Adds a default route (for all addresses) via the local gateway
           192.168.1.1 that can be reached on device eth0.

SEE ALSO

       ip(8)

AUTHOR

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