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


       ip [ OPTIONS ] OBJECT { COMMAND | help }

       OBJECT := { link | addr | addrlabel | 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 } |

               allmulticast { on | off } |

               dynamic { on | off } |

               multicast { on | off } |

               txqueuelen PACKETS |

               name NEWNAME |

               address LLADDR | broadcast LLADDR |

               mtu MTU |

               netns PID |

               alias NAME |

               vf NUM [ mac LLADDR ] [ vlan VLANID [ qos VLAN-QOS ] ] [ rate TXRATE ]  }

       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 addrlabel { add | del } prefix PREFIX [ dev DEV ] [ label NUMBER ]

       ip addrlabel { list | flush }

       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 TIME ] [ rttvar TIME ] [ window NUMBER ] [ cwnd NUMBER ] [ initcwnd NUMBER ] [

               ssthresh REALM ] [ realms REALM ] [ rto_min TIME ]

       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 | flush ] SELECTOR ACTION

       SELECTOR := [ from PREFIX ] [ to PREFIX ] [ tos TOS ] [ fwmark FWMARK[/MASK] ] [ 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 | prl } [ NAME ]

               [ mode MODE ] [ remote ADDR ] [ local ADDR ]

               [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ] ]

               [ encaplimit ELIM ] [ ttl TTL ]

               [ tos TOS ] [ flowlabel FLOWLABEL ]

               [ prl-default ADDR ] [ prl-nodefault ADDR ] [ prl-delete ADDR ]

               [ [no]pmtudisc ] [ dev PHYS_DEV ] [ dscp inherit ]

       MODE :=  { ipip | gre | sit | isatap | ip6ip6 | ipip6 | any }

       ADDR := { IP_ADDRESS | any }

TOS := { NUMBER | inherit }

       ELIM := { none | 0..255 }

       TTL := { 1..255 | inherit }

       KEY := { DOTTED_QUAD | NUMBER }

       TIME := NUMBER[s|ms|us|ns|j]

       ip maddr [ add | del ] MULTIADDR dev STRING

       ip maddr show [ dev STRING ]

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

       ip monitor [ all | LISTofOBJECTS ]

       ip xfrm XFRM_OBJECT { COMMAND }

       XFRM_OBJECT := { state | policy | monitor }

       ip xfrm state { add | update } ID [ XFRM_OPT ]  [ mode MODE ]

                [ reqid REQID ]  [ seq SEQ ]  [ replay-window SIZE ]

                [ flag FLAG-LIST ]  [ encap ENCAP ]  [ sel SELECTOR ]

                [ LIMIT-LIST ]

       ip xfrm state allocspi ID  [ mode MODE ]  [ reqid REQID ]  [ seq SEQ ]  [ min SPI max SPI ]

       ip xfrm state { delete | get } ID

       ip xfrm state { deleteall | list } [ ID ]  [ mode MODE ]

                [ reqid REQID ]  [ flag FLAG_LIST ]

       ip xfrm state flush [ proto XFRM_PROTO ]

       ip xfrm state count

       ID :=  [ src ADDR ]  [ dst ADDR ]  [ proto XFRM_PROTO ]  [ spi SPI ]

       XFRM_PROTO :=  [ esp | ah | comp | route2 | hao ]

       MODE :=  [ transport | tunnel | ro | beet ] (default=transport)


FLAG :=  [ noecn | decap-dscp | wildrecv ]


       ENCAP-TYPE := espinudp  | espinudp-nonike

       ALGO-LIST := [ ALGO-LIST ] | [ ALGO ]


       ALGO_TYPE :=  [ enc | auth | comp ]

       SELECTOR := src ADDR[/PLEN] dst ADDR[/PLEN]  [ UPSPEC ]  [ dev DEV ]

       UPSPEC := proto PROTO [[ sport PORT ]  [ dport PORT ] |

                [ type NUMBER ]  [ code NUMBER ]]

       LIMIT-LIST := [ LIMIT-LIST ] |  [ limit LIMIT ]

       LIMIT :=  [ [time-soft|time-hard|time-use-soft|time-use-hard] SECONDS ] | [ [byte-soft|byte-hard] SIZE ] |

                [ [packet-soft|packet-hard] COUNT ]

       ip xfrm policy { add | update }  dir DIR SELECTOR [ index INDEX ]

                [ ptype PTYPE ]  [ action ACTION ]  [ priority PRIORITY ]

                [ LIMIT-LIST ] [ TMPL-LIST ]

       ip xfrm policy { delete | get }  dir DIR [ SELECTOR | index INDEX  ]

                [ ptype PTYPE ]

       ip xfrm policy { deleteall | list }  [ dir DIR ] [ SELECTOR ]

                [ index INDEX ]  [ action ACTION ]  [ priority PRIORITY ]

       ip xfrm policy flush  [ ptype PTYPE ]

       ip xfrm count

       PTYPE :=  [ main | sub ] (default=main)

       DIR :=  [ in | out | fwd ]

       SELECTOR := src ADDR[/PLEN] dst ADDR[/PLEN] [ UPSPEC  ] [ dev DEV ]

       UPSPEC := proto PROTO [  [ sport PORT ]  [ dport PORT ] |

                [ type NUMBER ]  [ code NUMBER ] ]

       ACTION :=  [ allow | block ] (default=allow)

LIMIT-LIST :=  [ LIMIT-LIST ] |  [ limit LIMIT ]

       LIMIT :=  [ [time-soft|time-hard|time-use-soft|time-use-hard] SECONDS ] |  [ [byte-soft|byte-hard] SIZE ] |

               [packet-soft|packet-hard] NUMBER ]

       TMPL-LIST :=  [ TMPL-LIST ] |  [ tmpl TMPL ]

       TMPL := ID [ mode MODE ]  [ reqid REQID ]  [ level LEVEL ]

       ID :=  [ src ADDR ]  [ dst ADDR ]  [ proto XFRM_PROTO ]  [ spi SPI ]

       XFRM_PROTO :=  [ esp | ah | comp | route2 | hao ]

       MODE :=  [ transport | tunnel | beet ] (default=transport)

       LEVEL :=  [ required | use ] (default=required)

       ip xfrm 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  net-

              working 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 ’\´ 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.


              - label configuration for protocol address selection.


              - 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.

       xfrm   - framework for IPsec protocol.

       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. When configuring SR-IOV Virtual Fuction (VF) devices, this keyword should specify

              the associated Physical Function (PF) device.

       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  con-


       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.

       netns PID

              move the device to the network namespace associated with the process PID.

       alias NAME

              give the device a symbolic name for easy reference.

       vf NUM specify a Virtual Function device to be configured. The associated PF device must be specified using the dev parameter.

                      mac LLADDRESS - change the station address for the specified VF. The vf parameter must be specified.

                      vlan  VLANID  -  change  the  assigned  VLAN for the specified VF. When specified, all traffic sent from the VF will be

                      tagged with the specified VLAN ID. Incoming traffic will be filtered for the specified VLAN ID, and will have all  VLAN

                      tags  stripped  before  being passed to the VF. Setting this parameter to 0 disables VLAN tagging and filtering. The vf

                      parameter must be specified.

vlan  VLANID  -  change  the  assigned  VLAN for the specified VF. When specified, all traffic sent from the VF will be

                      tagged with the specified VLAN ID. Incoming traffic will be filtered for the specified VLAN ID, and will have all  VLAN

                      tags  stripped  before  being passed to the VF. Setting this parameter to 0 disables VLAN tagging and filtering. The vf

                      parameter must be specified.

                      qos VLAN-QOS - assign VLAN QOS (priority) bits for the VLAN tag. When specified, all VLAN tags transmitted  by  the  VF

                      will  include  the specified priority bits in the VLAN tag. If not specified, the value is assumed to be 0. Both the vf

                      and vlan parameters must be specified. Setting both vlan and qos as 0 disables VLAN tagging and filtering for the VF.

                      rate TXRATE - change the allowed transmit bandwidth, in Mbps, for the specified VF.  Setting this parameter to  0  dis-

                      ables rate limiting. The vf parameter must be specified.

       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 discrimi-

       nated, 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 ’+’ and ’-’ instead of the broadcast address.  In this case, the broadcast address is

              derived by setting/resetting the host bits of the interface prefix.

       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.  Prede-

              fined 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  argu-

       ments 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 subsection.

ip addrlabel - protocol address label management.

       IPv6  address label is used for address selection described in RFC 3484.  Precedence is managed by userspace, and only label is stored

       in kernel.

   ip addrlabel add - add an address label

       the command adds an address label entry to the kernel.

       prefix PREFIX

       dev DEV

              the outgoing interface.

       label NUMBER

              the label for the prefix.  0xffffffff is reserved.

   ip addrlabel del - delete an address label

       the command deletes an address label entry in the kernel.  Arguments: coincide with the arguments of ip addrlabel add but label is not


   ip addrlabel list - list address labels

       the command show contents of address labels.

   ip addrlabel flush - flush address labels

       the command flushes the contents of address labels and it does not restore default settings.

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 null.

       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.  Particu-

       larly, 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 pro-

               hibited 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 termi-

               nated 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


               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 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 255 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.

       Actually, one other table always exists, which is invisible but even more important.  It is the local table (ID 255).  This table con-

       sists 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 ta-

              ble 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.

       r 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 compatability with previous releases.  Otherwise if a suffix of s, sec or secs is used to specify seconds; ms,

              msec or msecs to specify milliseconds; us, usec or usecs to specify microseconds; ns, nsec or nsecs to specify nanoseconds;  j,

              hz or jiffies to specify jiffies, the value is converted to what the routing code expects.

       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


       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

              the maximum initial congestion window (cwnd) size in MSS of a TCP connection.

       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 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.


              allow packet by packet randomization on multipath routes.  Without this modifier, the route will be frozen to one selected nex-

              thop, 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 PREFIX.

       src PREFIX

              only list routes with preferred source addresses selected by PREFIX.

      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 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.


              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 rule - routing policy database management

       Rules in the routing policy database control the route selection algorithm.

Classic  routing  algorithms used in the Internet make routing decisions based only on the destination address of packets (and in the-

       ory, 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 device.

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

       1.     Priority: 0, Selector: match anything, Action: lookup routing table local (ID 255).  The local table is a special routing table

              containing high priority control routes for local and broadcast addresses.

              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 them.

       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.  The options  preference  and  order

              are synonyms with priority.

       table TABLEID

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

       realms FROM/TO

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

              any realm.

       nat ADDRESS

              The base of the IP address block to translate (for source addresses).  The ADDRESS may be either the start of the block of  NAT

              addresses  (selected by NAT routes) or a local host address (or even zero).  In the last case the router does not translate the

              packets, but masquerades them to this address.  Using map-to instead of nat means the same thing.

              Warning: Changes to the RPDB made with these commands do not become active immediately.  It is assumed that after a script fin-

              ishes a batch of updates, it flushes the routing cache with ip route flush cache.

   ip rule flush - also dumps all the deleted rules.

       This command has no arguments.

   ip rule show - list rules

       This command has no arguments.  The options list or lst are synonyms with show.

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 addresses.

       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 administra-

       tively, 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 list.

       iif NAME

              the interface on which multicast packets are received.

       from PREFIX

              the prefix selecting the IP source addresses of the multicast route.

ip tunnel - tunnel configuration

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

       (or outer) address family is specified by the -f option.  The default is IPv4.

   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. Available modes depend on the encapsulating address family.

              Modes for IPv4 encapsulation available: ipip, sit, isatap and gre.

              Modes for IPv6 encapsulation available: ip6ip6, ipip6 and any.

       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 for IPv4 tunnels is: inherit.  The default value for IPv6 tunnels is: 64.

       tos T

       dsfield T

       tclass T

              set a fixed TOS (or traffic class in IPv6) T on tunneled packets.  The default value is: inherit.

       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  pack-

              ets.  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 isn’t work. Don’t use it.

       dscp inherit

 ( only IPv6 tunnels ) Inherit DS field between inner and outer header.

       encaplim ELIM

              ( only IPv6 tunnels ) set a fixed encapsulation limit.  Default is 4.

       flowlabel FLOWLABEL

              ( only IPv6 tunnels ) set a fixed flowlabel.

   ip tunnel prl - potential router list (ISATAP only)

       dev NAME

              mandatory device name.

       prl-default ADDR

       prl-nodefault ADDR

       prl-delete ADDR

              Add or delete ADDR as a potential router or default router.

   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  moni-

       tor.  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 start-


ip xfrm - setting xfrm

       xfrm is an IP framework, which can transform format of the datagrams,

       i.e. encrypt the packets with some algorithm. xfrm policy and xfrm state are associated through templates TMPL_LIST.   This  framework

       is used as a part of IPsec protocol.

ip xfrm state add - add new state into xfrm

   ip xfrm state update - update existing xfrm state

   ip xfrm state allocspi - allocate SPI value

       MODE   is set as default to transport, but it could be set to tunnel,ro or beet.


              contains one or more flags.

       FLAG   could be set to noecn, decap-dscp or wildrecv.

       ENCAP  encapsulation is set to encapsulation type ENCAP-TYPE, source port SPORT, destination port DPORT and OADDR.


              could be set to espinudp or espinudp-nonike.


              contains  one  or  more algorithms ALGO which depend on the type of algorithm set by ALGO_TYPE.  It can be used these algoritms

              enc, auth or comp.

   ip xfrm policy add - add a new policy

   ip xfrm policy update - update an existing policy

   ip xfrm policy delete - delete existing policy

   ip xfrm policy get - get existing policy

   ip xfrm policy deleteall - delete all existing xfrm policy

   ip xfrm policy list - print out the list of xfrm policy

   ip xfrm policy flush - flush policies

       It can be flush all policies or only those specified with ptype.

       dir DIR

              directory could be one of these: inp, out or fwd.


              selects for which addresses will be set up the policy. The selector is defined by source and destination address.

       UPSPEC is defined by source port sport, destination port dport, type as number and code also number.

       dev DEV

              specify network device.

       index INDEX

              the number of indexed policy.

       ptype PTYPE

              type is set as default on main, could be switch on sub.

action ACTION

              is set as default on allow.  It could be switch on block.

       priority PRIORITY

              priority is a number. Default priority is set on zero.


              limits are set in seconds, bytes or numbers of packets.


              template list is based on ID, mode, reqid and level.

       ID     is specified by source address, destination address, proto and value of spi.


              values: esp, ah, comp, route2 or hao.

       MODE   is set as default on transport, but it could be set on tunnel or beet.

       LEVEL  is set as default on required and the other choice is use.

       UPSPEC is specified by sport, dport, type and code (NUMBER).

   ip xfrm monitor - is used for listing all objects or defined group of them.

       The xfrm monitor can monitor the policies for all objects or defined group of them.