bionic (8) ip-route.8.gz

Provided by: iproute2_4.15.0-2ubuntu1.3_amd64 bug

NAME

       ip-route - routing table management

SYNOPSIS

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

       ip route { show | flush } SELECTOR

       ip route save SELECTOR

       ip route restore

       ip route get ROUTE_GET_FLAGS ADDRESS [ from ADDRESS iif STRING  ] [ oif STRING ] [ mark MARK ] [ tos TOS
               ] [ vrf NAME ]

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

       SELECTOR := [ root PREFIX ] [ match PREFIX ] [ exact PREFIX ] [ table TABLE_ID ] [ vrf NAME ] [ 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 ] [ ttl-propagate { enabled | disabled } ]

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

       NH := [ encap ENCAP ] [ 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 ] [ expires TIME ] [ fastopen_no_cookie BOOL ]

       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 ]

       ENCAP := [ MPLS | IP | BPF | SEG6 | SEG6LOCAL ]

       ENCAP_MPLS := mpls [ LABEL ] [ ttl TTL ]

       ENCAP_IP := ip id TUNNEL_ID dst REMOTE_IP [ tos TOS ] [ ttl TTL ]

       ENCAP_BPF := bpf [ in PROG ] [ out PROG ] [ xmit PROG ] [ headroom SIZE ]

       ENCAP_SEG6 := seg6 mode [ encap | inline | l2encap ] segs SEGMENTS [ hmac KEYID ]

       ENCAP_SEG6LOCAL := seg6local action SEG6_ACTION [ SEG6_ACTION_PARAM ]

       ROUTE_GET_FLAGS :=  [ fibmatch  ]

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 2^32-1 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, where routes with
                     lower values are preferred.

              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.

              vrf NAME
                     the vrf name to add this route to. Implicitly means the table associated with the VRF.

              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.

              fastopen_no_cookie BOOL (4.15+ only)
                     Enable TCP Fastopen without a cookie 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

              encap ENCAPTYPE ENCAPHDR
                     attach tunnel encapsulation attributes to this route.

                     ENCAPTYPE is a string specifying the supported encapsulation type. Namely:

                             mpls - encapsulation type MPLS

                             ip - IP encapsulation (Geneve, GRE, VXLAN, ...)

                             bpf - Execution of BPF program

                             seg6 - encapsulation type IPv6 Segment Routing

                             seg6local - local SRv6 segment processing

                     ENCAPHDR is a set of encapsulation attributes specific to the ENCAPTYPE.

                             mpls
                               MPLSLABEL - mpls label stack with labels separated by /

                               ttl TTL - TTL to use for MPLS header or 0 to inherit from IP header

                             ip
                               id TUNNEL_ID dst REMOTE_IP [ tos TOS ] [ ttl TTL ]

                             bpf
                               in PROG - BPF program to execute for incoming packets

                               out PROG - BPF program to execute for outgoing packets

                               xmit PROG - BPF program to execute for transmitted packets

                               headroom SIZE - Size of header BPF program will attach (xmit)

                             seg6
                               mode inline - Directly insert Segment Routing Header after IPv6 header

                               mode encap - Encapsulate packet in an outer IPv6 header with SRH

                               mode l2encap - Encapsulate ingress L2 frame within an outer IPv6 header and SRH

                               SEGMENTS - List of comma-separated IPv6 addresses

                               KEYID - Numerical value in decimal representation. See ip-sr(8).

                             seg6local
                               SEG6_ACTION [ SEG6_ACTION_PARAM ] - Operation to perform on matching packets.
                               The following actions are currently supported (4.14+ only).

                                 End - Regular SRv6 processing as intermediate segment endpoint.  This action
                                 only accepts packets with a non-zero Segments Left value. Other matching
                                 packets are dropped.

                                 End.X nh6 NEXTHOP - Regular SRv6 processing as intermediate segment endpoint.
                                 Additionally, forward processed packets to given next-hop.  This action only
                                 accepts packets with a non-zero Segments Left value. Other matching packets are
                                 dropped.

                                 End.DX6 nh6 NEXTHOP - Decapsulate inner IPv6 packet and forward it to the
                                 specified next-hop. If the argument is set to ::, then the next-hop is selected
                                 according to the local selection rules. This action only accepts packets with
                                 either a zero Segments Left value or no SRH at all, and an inner IPv6 packet.
                                 Other matching packets are dropped.

                                 End.B6 srh segs SEGMENTS [ hmac KEYID ] - Insert the specified SRH immediately
                                 after the IPv6 header, update the DA with the first segment of the newly
                                 inserted SRH, then forward the resulting packet. The original SRH is not
                                 modified. This action only accepts packets with a non-zero Segments Left value.
                                 Other matching packets are dropped.

                                 End.B6.Encaps srh segs SEGMENTS [ hmac KEYID ] - Regular SRv6 processing as
                                 intermediate segment endpoint.  Additionally, encapsulate the matching packet
                                 within an outer IPv6 header followed by the specified SRH. The destination
                                 address of the outer IPv6 header is set to the first segment of the new SRH.
                                 The source address is set as described in ip-sr(8).

              expires TIME (4.4+ only)
                     the route will be deleted after the expires time.  Only support IPv6 at present.

              ttl-propagate { enabled | disabled }
                     Control whether TTL should be propagated from any encap into the un-encapsulated packet,
                     overriding any global configuration. Only supported for MPLS at present.

       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.

              vrf NAME
                     show the routes for the table associated with the vrf name

              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.

              fibmatch
                     Return full fib lookup matched route. Default is to return the resolved dst entry

              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.

              mark MARK
                     the firewall mark (fwmark)

              vrf NAME
                     force the vrf 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.

NOTES

       Starting with Linux kernel version 3.6, there is no routing cache for IPv4 anymore. Hence ip route show
       cached will never print any entries on systems with this or newer kernel versions.

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.

       ip route add 10.1.1.0/30 encap mpls 200/300 via 10.1.1.1 dev eth0
           Adds an ipv4 route with mpls encapsulation attributes attached to it.

       ip -6 route add 2001:db8:1::/64 encap seg6 mode encap segs 2001:db8:42::1,2001:db8:ffff::2 dev eth0
           Adds an IPv6 route with SRv6 encapsulation and two segments attached.

SEE ALSO

       ip(8)

AUTHOR

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