Provided by: iproute_20041019-4ubuntu5_i386 bug


       ip - show / manipulate routing, devices, policy routing and tunnels


       ip [ OPTIONS ] OBJECT { COMMAND | help }

       OBJECT := { link | addr | route | rule | neigh | tunnel | maddr |
               mroute | monitor }

       OPTIONS := { -V[ersion] | -s[tatistics] | -r[esolve] | -f[amily] { inet
               | inet6 | ipx | dnet | link } | -o[neline] }

       ip link set DEVICE { up | down | arp { on | off } |
               promisc { on | off } |
               allmulti { on | off } |
               dynamic { on | off } |
               multicast { on | off } |
               txqueuelen PACKETS |
               name NEWNAME |
               address LLADDR | broadcast LLADDR |
               mtu MTU }

       ip link show [ DEVICE ]

       ip addr { add | del } IFADDR dev STRING

       ip addr { show | flush } [ dev STRING ] [ scope SCOPE-ID ] [ to PREFIX
               ] [ FLAG-LIST ] [ label PATTERN ]

       IFADDR := PREFIX | ADDR peer PREFIX [ broadcast ADDR ] [ anycast ADDR ]
               [ label STRING ] [ scope SCOPE-ID ]

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


       FLAG := [ permanent | dynamic | secondary | primary | tentative |
               deprecated ]

       ip route { list | flush } SELECTOR

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

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

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


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

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

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

       OPTIONS := FLAGS [ mtu NUMBER ] [ advmss NUMBER ] [ rtt NUMBER ] [
               rttvar NUMBER ] [ window NUMBER ] [ cwnd NUMBER ] [ ssthresh
               REALM ] [ realms REALM ]

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

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

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

       FLAGS := [ equalize ]

       NHFLAGS := [ onlink | pervasive ]

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

       ip rule  [ list | add | del ] SELECTOR ACTION

       SELECTOR := [ from PREFIX ] [ to PREFIX ] [ tos TOS ] [ fwmark FWMARK ]
               [ dev STRING ] [ pref NUMBER ]

       ACTION := [ table TABLE_ID ] [ nat ADDRESS ] [ prohibit | reject |
               unreachable ] [ realms [SRCREALM/]DSTREALM ]

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

       ip neigh { add | del | change | replace } { ADDR [ lladdr LLADDR ] [
               nud { permanent | noarp | stale | reachable } ] | proxy ADDR }
               [ dev DEV ]

       ip neigh { show | flush } [ to PREFIX ] [ dev DEV ] [ nud STATE ]

       ip tunnel { add | change | del | show } [ NAME ]
               [ mode { ipip | gre | sit } ]
               [ remote ADDR ] [ local ADDR ]
               [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ] ]
               [ ttl TTL ] [ tos TOS ] [ [no]pmtudisc ]
               [ dev PHYS_DEV ]

       ADDR := { IP_ADDRESS | any }

       TOS := { NUMBER | inherit }

       TTL := { 1..255 | inherit }

       KEY := { DOTTED_QUAD | NUMBER }

       ip maddr [ add | del ] MULTIADDR dev STRING

       ip maddr show [ dev STRING ]

       ip mroute show [ PREFIX ] [ from PREFIX ] [ iif DEVICE ]

       ip monitor [ all | LISTofOBJECTS ]


       -V, -Version
              print the version of the ip utility and exit.

       -s, -stats, -statistics
              output more information.  If the option appears twice  or  more,
              the amount of information increases.  As a rule, the information
              is statistics or some time values.

       -f, -family
              followed by protocol family  identifier:  inet,  inet6  or  link
              ,enforce  the  protocol  family  to  use.   If the option is not
              present, the protocol family is guessed  from  other  arguments.
              If the rest of the command line does not give enough information
              to guess the family, ip falls back to the default  one,  usually
              inet  or  any.  link is a special family identifier meaning that
              no networking protocol is involved.

       -4     shortcut for -family inet.

       -6     shortcut for -family inet6.

       -0     shortcut for -family link.

       -o, -oneline
              output each record on a single line, replacing line  feeds  with
              the  â€â€™\´  character.  This  is convenient when you want to count
              records with wc(1)
               or to grep(1) the output.

       -r, -resolve
              use the system’s name resolver to print  DNS  names  instead  of
              host addresses.


       link   - network device.

              - protocol (IP or IPv6) address on a device.

              - ARP or NDISC cache entry.

       route  - routing table entry.

       rule   - rule in routing policy database.

              - multicast address.

       mroute - multicast routing cache entry.

       tunnel - tunnel over IP.

       The  names  of  all objects may be written in full or abbreviated form,
       f.e.  address is abbreviated as addr or just a.

       Specifies the action to perform on the object.   The  set  of  possible
       actions  depends on the object type.  As a rule, it is possible to add,
       delete and show (or list ) objects, but some objects do not  allow  all
       of these operations or have some additional commands.  The help command
       is available for all objects.   It  prints  out  a  list  of  available
       commands and argument syntax conventions.

       If no command is given, some default command is assumed.  Usually it is
       list or, if the objects of this class cannot be listed, help.

ip link - network device configuration

       link is a network device and the  corresponding  commands  display  and
       change the state of devices.

   ip link set - change device attributes
       dev NAME (default)
              NAME specifies network device to operate on.

       up and down
              change the state of the device to UP or DOWN.

       arp on or arp off
              change the NOARP flag on the device.

       multicast on or multicast off
              change the MULTICAST flag on the device.

       dynamic on or dynamic off
              change the DYNAMIC flag on the device.

       name NAME
              change   the   name  of  the  device.   This  operation  is  not
              recommended if the device  is  running  or  has  some  addresses
              already configured.

       txqueuelen NUMBER

       txqlen NUMBER
              change the transmit queue length of the device.

       mtu NUMBER
              change the MTU of the device.

       address LLADDRESS
              change the station address of the interface.

       broadcast LLADDRESS

       brd LLADDRESS

       peer LLADDRESS
              change the link layer broadcast address or the peer address when
              the interface is POINTOPOINT.

       Warning:  If  multiple  parameter  changes  are  requested,  ip  aborts
       immediately  after  any  of  the changes have failed.  This is the only
       case when ip can move  the  system  to  an  unpredictable  state.   The
       solution  is  to avoid changing several parameters with one ip link set

   ip link show - display device attributes
       dev NAME (default)
              NAME specifies the network device to show.  If this argument  is
              omitted all devices are listed.

       up     only display running interfaces.

ip address - protocol address management.

       The  address  is  a protocol (IP or IPv6) address attached to a network
       device.  Each device  must  have  at  least  one  address  to  use  the
       corresponding  protocol.   It  is  possible  to  have several different
       addresses  attached  to  one   device.    These   addresses   are   not
       discriminated, so that the term alias is not quite appropriate for them
       and we do not use it in this document.

       The ip addr command displays addresses and their properties,  adds  new
       addresses and deletes old ones.

   ip address add - add new protocol address.
       dev NAME
              the name of the device to add the address to.

       local ADDRESS (default)
              the  address of the interface. The format of the address depends
              on the protocol. It is a dotted quad for IP and  a  sequence  of
              hexadecimal halfwords separated by colons for IPv6.  The ADDRESS
              may be followed by a slash and a decimal  number  which  encodes
              the network prefix length.

       peer ADDRESS
              the  address  of the remote endpoint for pointopoint interfaces.
              Again, the ADDRESS may be followed by  a  slash  and  a  decimal
              number,  encoding  the network prefix length.  If a peer address
              is specified, the local address cannot  have  a  prefix  length.
              The  network prefix is associated with the peer rather than with
              the local address.

       broadcast ADDRESS
              the broadcast address on the interface.

              It is possible to use the special symbols â€â€™+â€â€™ and â€â€™-â€â€™ instead of
              the  broadcast  address.  In this case, the broadcast address is
              derived by setting/resetting the  host  bits  of  the  interface

       label NAME
              Each  address  may  be  tagged with a label string.  In order to
              preserve compatibility with Linux-2.0 net aliases,  this  string
              must  coincide  with  the name of the device or must be prefixed
              with the device name followed by colon.

       scope SCOPE_VALUE
              the scope  of  the  area  where  this  address  is  valid.   The
              available  scopes  are  listed  in file /etc/iproute2/rt_scopes.
              Predefined scope values are:

                      global - the address is globally valid.

                      site - (IPv6 only) the address is site local, i.e. it is
                      valid inside this site.

                      link  - the address is link local, i.e. it is valid only
                      on this device.

                      host - the address is valid only inside this host.

   ip address delete - delete protocol address
       Arguments: coincide with the arguments of ip addr add.  The device name
       is  a  required  argument.  The rest are optional.  If no arguments are
       given, the first address is deleted.

   ip address show - look at protocol addresses
       dev NAME (default)
              name of device.

       scope SCOPE_VAL
              only list addresses with this scope.

       to PREFIX
              only list addresses matching this prefix.

       label PATTERN
              only list addresses with labels matching the  PATTERN.   PATTERN
              is a usual shell style pattern.

       dynamic and permanent
              (IPv6  only)  only  list  addresses  installed  due to stateless
              address configuration  or  only  list  permanent  (not  dynamic)

              (IPv6  only)  only  list  addresses which did not pass duplicate
              address detection.

              (IPv6 only) only list deprecated addresses.

       primary and secondary
              only list primary (or secondary) addresses.

   ip address flush - flush protocol addresses
       This command flushes the protocol addresses selected by some  criteria.

       This command has the same arguments as show.  The difference is that it
       does not run when no arguments are given.

       Warning: This command (and other flush  commands  described  below)  is
       pretty  dangerous.   If you make a mistake, it will not forgive it, but
       will cruelly purge all the addresses.

       With the -statistics option, the command becomes verbose. It prints out
       the  number of deleted addresses and the number of rounds made to flush
       the address list.  If this option is given twice, ip  addr  flush  also
       dumps all the deleted addresses in the format described in the previous

ip neighbour - neighbour/arp tables management.

       neighbour objects establish bindings  between  protocol  addresses  and
       link  layer  addresses  for  hosts  sharing  the  same link.  Neighbour
       entries are organized into tables. The IPv4 neighbour table is known by
       another name - the ARP table.

       The   corresponding  commands  display  neighbour  bindings  and  their
       properties, add new neighbour entries and delete old ones.

   ip neighbour add - add a new neighbour entry
   ip neighbour change - change an existing entry
   ip neighbour replace - add a new entry or change an existing one
       These commands create new neighbour records or update existing ones.

       to ADDRESS (default)
              the protocol address of the neighbour. It is either an  IPv4  or
              IPv6 address.

       dev NAME
              the interface to which this neighbour is attached.

       lladdr LLADDRESS
              the  link layer address of the neighbour.  LLADDRESS can also be

       nud NUD_STATE
              the state of the neighbour entry.  nud is  an  abbreviation  for
              ’Neigh  bour  Unreachability Detection’.  The state can take one
              of the following values:

                      permanent - the neighbour entry is valid forever and can
                      be only be removed administratively.

                      noarp  -  the  neighbour  entry is valid. No attempts to
                      validate this entry will be made but it can  be  removed
                      when its lifetime expires.

                      reachable  -  the  neighbour  entry  is  valid until the
                      reachability timeout expires.

                      stale - the neighbour entry  is  valid  but  suspicious.
                      This  option  to  ip neigh does not change the neighbour
                      state if it was valid and the address is not changed  by
                      this command.

   ip neighbour delete - delete a neighbour entry
       This command invalidates a neighbour entry.

       The arguments are the same as with ip neigh add, except that lladdr and
       nud are ignored.

       Warning: Attempts to delete or manually change a noarp entry created by
       the  kernel  may  result in unpredictable behaviour.  Particularly, the
       kernel may try to resolve this address even on a NOARP interface or  if
       the address is multicast or broadcast.

   ip neighbour show - list neighbour entries
       This commands displays neighbour tables.

       to ADDRESS (default)
              the prefix selecting the neighbours to list.

       dev NAME
              only list the neighbours attached to this device.

       unused only list neighbours which are not currently in use.

       nud NUD_STATE
              only  list  neighbour  entries  in  this state.  NUD_STATE takes
              values listed below or the special value  all  which  means  all
              states.   This  option may occur more than once.  If this option
              is absent, ip lists all entries except for none and noarp.

   ip neighbour flush - flush neighbour entries
       This command flushes neighbour tables, selecting entries  to  flush  by
       some criteria.

       This  command has the same arguments as show.  The differences are that
       it does not run when no arguments  are  given,  and  that  the  default
       neighbour states to be flushed do not include permanent and noarp.

       With  the  -statistics  option, the command becomes verbose.  It prints
       out the number of deleted neighbours and the number of rounds  made  to
       flush  the  neighbour  table.   If  the option is given twice, ip neigh
       flush also dumps all the deleted neighbours.

ip route - routing table management

       Manipulate route entries in the kernel routing tables keep  information
       about paths to other networked nodes.

       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

               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.

               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 255 or by name from the
       file /etc/iproute2/rt_tables main table (ID 254) and  the  kernel  only
       uses this table when calculating routes.

       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

       metric NUMBER

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

       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 ADDRESS
              the address of the nexthop router.  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 NUMBER
              the initial RTT (’Round Trip Time’) estimate.

       rttvar NUMBER (2.3.15+ only)
              the initial RTT variance estimate.

       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.

       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

       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 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

       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

                      kernel - the route was installed by  the  kernel  during

                      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

              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.

              allow  packet  by  packet  randomization  on  multipath  routes.
              Without  this modifier, the route will be frozen to one selected
              nexthop, so that load splitting  will  only  occur  on  per-flow
              base.  equalize only works if the kernel is patched.

   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 tablemain.  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.


       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 PREFIX
              only  list  routes  going  via  the  nexthop routers selected by

       src PREFIX
              only list routes with preferred  source  addresses  selected  by

       realm REALMID

              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

   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.

              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

       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 rule - routing policy database management

       Rules in the  routing  policy  database  control  the  route  selection

       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 the order  of  increasing  priority.
       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 on the next rule.

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

       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.

              Rule 0 is special. It cannot be deleted or overridden.

       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

       tos TOS

       dsfield TOS
              select the TOS value to match.

       fwmark MARK
              select the fwmark value to match.

       priority PREFERENCE
              the  priority of this rule.  Each rule should have an explicitly
              set unique priority value.

       table TABLEID
              the routing table identifier to  lookup  if  the  rule  selector

       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.

              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 show - list rules
       This command has no arguments.

ip maddress - multicast addresses management

       maddress objects are multicast addresses.

   ip maddress show - list multicast addresses
       dev NAME (default)
              the device name.

   ip maddress add - add a multicast address
   ip maddress delete - delete a multicast address
       these commands attach/detach a static link layer multicast  address  to
       listen  on  the interface.  Note that it is impossible to join protocol
       multicast groups statically.  This  command  only  manages  link  layer

       address LLADDRESS (default)
              the link layer multicast address.

       dev NAME
              the device to join/leave this multicast address.

ip mroute - multicast routing cache management

       mroute  objects  are  multicast routing cache entries created by a user
       level mrouting daemon (f.e.  pimd or mrouted ).

       Due to the limitations  of  the  current  interface  to  the  multicast
       routing   engine,   it   is   impossible   to   change  mroute  objects
       administratively, so we may only display them.  This limitation will be
       removed in the future.

   ip mroute show - list mroute cache entries
       to PREFIX (default)
              the  prefix  selecting  the  destination  multicast addresses to

       iif NAME
              the interface on which multicast packets are received.

       from PREFIX
              the prefix selecting the IP source addresses  of  the  multicast

ip tunnel - tunnel configuration

       tunnel  objects  are tunnels, encapsulating packets in IPv4 packets and
       then sending them over the IP infrastructure.

   ip tunnel add - add a new tunnel
   ip tunnel change - change an existing tunnel
   ip tunnel delete - destroy a tunnel
       name NAME (default)
              select the tunnel device name.

       mode MODE
              set the tunnel mode.  Three modes are currently available: ipip,
              sit and gre.

       remote ADDRESS
              set the remote endpoint of the tunnel.

       local ADDRESS
              set the fixed local address for tunneled packets.  It must be an
              address on another interface of this host.

       ttl N  set a fixed TTL N on tunneled packets.  N is  a  number  in  the
              range  1--255. 0 is a special value meaning that packets inherit
              the TTL value.  The default value is: inherit.

       tos T

       dsfield T
              set a fixed TOS T on tunneled packets.  The  default  value  is:

       dev NAME
              bind the tunnel to the device NAME so that tunneled packets will
              only be routed via this device and will not be able to escape to
              another device when the route to endpoint changes.

              disable  Path  MTU  Discovery  on this tunnel.  It is enabled by
              default.  Note that  a  fixed  ttl  is  incompatible  with  this
              option: tunnelling with a fixed ttl always makes pmtu discovery.

       key K

       ikey K

       okey K ( only GRE tunnels ) use keyed GRE with key K.  K  is  either  a
              number  or  an  IP  address-like dotted quad.  The key parameter
              sets the key to use in  both  directions.   The  ikey  and  okey
              parameters set different keys for input and output.

       csum, icsum, ocsum
              (  only  GRE  tunnels  ) generate/require checksums for tunneled
              packets.  The  ocsum  flag  calculates  checksums  for  outgoing
              packets.   The  icsum  flag requires that all input packets have
              the correct checksum.   The  csum  flag  is  equivalent  to  the
              combination icsum ocsum.

       seq, iseq, oseq
              (  only  GRE tunnels ) serialize packets.  The oseq flag enables
              sequencing of outgoing packets.  The iseq flag requires that all
              input packets are serialized.  The seq flag is equivalent to the
              combination iseq oseq.  It isnâ€â€™t work. Donâ€â€™t use it.

   ip tunnel show - list tunnels
       This command has no arguments.

ip monitor and rtmon - state monitoring

       The ip utility can monitor the state of devices, addresses  and  routes
       continuously.   This  option  has a slightly different format.  Namely,
       the monitor command is the first in  the  command  line  and  then  the
       object list follows:

       ip monitor [ all | LISTofOBJECTS ]

       OBJECT-LIST  is  the  list of object types that we want to monitor.  It
       may contain link, address and route.  If no file argument is given,  ip
       opens  RTNETLINK,  listens  on it and dumps state changes in the format
       described in previous sections.

       If a file name is given, it does not listen on RTNETLINK, but opens the
       file  containing  RTNETLINK  messages  saved in binary format and dumps
       them.  Such a history file can be generated  with  the  rtmon  utility.
       This utility has a command line syntax similar to ip monitor.  Ideally,
       rtmon should be started before the first network configuration  command
       is issued. F.e. if you insert:

               rtmon file /var/log/rtmon.log

       in a startup script, you will be able to view the full history later.

       Certainly,  it is possible to start rtmon at any time.  It prepends the
       history with the state snapshot dumped at the moment of starting.


       ip was written by Alexey N. Kuznetsov and added in Linux 2.2.


       IP Command reference
       IP tunnels


       Manpage maintained by Michail Litvak <>