1. NAME

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

2. SYNOPSIS

ip "[ " OPTIONS " ] " OBJECT " { " COMMAND " | "

R help

OBJECT " := { "

R link tunnel " | " maddr " | " mroute " | " monitor " }"

OPTIONS " := { " -V[ersion] | -s[tatistics] | -r[esolve] | -f[amily] {

R inet -o[neline] } ip link add link DEVICE "[ " name " ]" NAME
"[ " txqueuelen PACKETS " ]"
"[ " address LLADDR " ]" "[ " broadcast LLADDR " ]"
"[ " mtu MTU " ]"

R type TYPE "[ " ARGS " ]" TYPE " := [ "

R vlan ip link delete DEVICE type TYPE "[ " ARGS " ]" ip link set DEVICE "{ " up " | " down " | " arp " { " on " | " off " } |"

R promisc

R allmulticast

R dynamic

R multicast

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 " ]"

R .IB IFADDR " dev " STRING

R 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-LIST " := [ " FLAG-LIST " ] " FLAG FLAG " := " "[ " permanent " | " dynamic " | " secondary " | " primary " | "\ tentative " | " deprecated " | " dadfailed " | " temporary " ]"

R

R PREFIX

dev DEV " ] [ "

label NUMBER " ]"

R

R

R list SELECTOR

ip route get ADDRESS " [ " from ADDRESS iif STRING " ] [ " oif STRING " ] [ "

tos TOS " ]"

R replace " | " monitor " } " ROUTE SELECTOR " := " "[ " root PREFIX " ] [ "

match PREFIX " ] [ "

exact PREFIX " ] [ "

table TABLE_ID " ] [ "

proto RTPROTO " ] [ "

type TYPE " ] [ "

scope SCOPE " ]" ROUTE " := " NODE_SPEC " [ " INFO_SPEC " ]" NODE_SPEC " := [ " TYPE " ] " PREFIX " ["

tos TOS " ] [ "

table TABLE_ID " ] [ "

proto RTPROTO " ] [ "

scope SCOPE " ] [ "

metric METRIC " ]" INFO_SPEC " := " "NH OPTIONS FLAGS" " ["

nexthop NH " ] ..." NH " := [ "

via ADDRESS " ] [ "

dev STRING " ] [ "

weight NUMBER " ] " NHFLAGS OPTIONS " := " FLAGS " [ "

mtu NUMBER " ] [ "

advmss NUMBER " ] [ "

rtt TIME " ] [ "

rttvar TIME " ] [ "

window NUMBER " ] [ "

cwnd NUMBER " ] [ "

ssthresh REALM " ] [ "

realms REALM " ] [ "

rto_min TIME " ] [ "

initcwnd NUMBER " ] [ "

initrwnd NUMBER " ]" TYPE " := [ "

R unicast throw " | " unreachable " | " prohibit " | " blackhole " | " nat " ]" TABLE_ID " := [ "

R local NUMBER " ]" SCOPE " := [ "

R host NUMBER " ]" NHFLAGS " := [ "

R onlink RTPROTO " := [ "

R kernel NUMBER " ]"

ip rule " [ " list " | " add " | " del " | " flush " ]" SELECTOR ACTION SELECTOR " := [ "

from PREFIX " ] [ "

to PREFIX " ] [ "

tos TOS " ] [ "

fwmark FWMARK[/MASK] " ] [ "

iif STRING " ] [ "

oif STRING " ] [ "

pref NUMBER " ]" ACTION " := [ "

table TABLE_ID " ] [ "

nat ADDRESS " ] [ "

R prohibit "[" SRCREALM "/]" DSTREALM " ]" TABLE_ID " := [ "

R local NUMBER " ]"

R ADDR " [ "

lladdr LLADDR " ] [ "

R nud ADDR " } [ "

dev DEV " ]"

R PREFIX " ] [ "

dev DEV " ] [ "

nud STATE " ]"

R "[ " 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 " |"

R any TOS " := { " NUMBER " |"

R inherit ELIM " := {

R none 0 ".." 255 " }" TTL " := { " 1 ".." 255 " | "

R inherit KEY " := { " DOTTED_QUAD " | " NUMBER " }" TIME " := " NUMBER "[s|ms|us|ns|j]"

R .IB MULTIADDR " dev " STRING

R STRING " ]"

R PREFIX " ] [ "

from PREFIX " ] [ "

iif DEVICE " ]"

R LISTofOBJECTS " ]"

R XFRM_OBJECT " { " COMMAND " }" XFRM_OBJECT " := { " state " | " policy " | " monitor " } "

R ID " [ " XFRM_OPT " ] " " [ " mode MODE " ] "
" [ " reqid REQID " ] " " [ " seq SEQ " ] " " [ " replay-window SIZE " ] "
" [ " flag FLAG-LIST " ] " " [ " encap ENCAP " ] " " [ " sel SELECTOR " ] "
" [ " LIMIT-LIST " ] "

R ID " [ " mode MODE " ] " " [ " reqid REQID " ] " " [ " seq SEQ " ] " " [ " min SPI

max SPI " ] "

R ID

R ID " ] " " [ " mode MODE " ] "
" [ " reqid REQID " ] " " [ " flag FLAG_LIST " ] "

R XFRM_PROTO " ] "

R 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-LIST " := " " [ " FLAG-LIST " ] " FLAG FLAG " := " " [ " noecn " | " decap-dscp " | " wildrecv " ] " ENCAP " := " ENCAP-TYPE " " SPORT " " DPORT " " OADDR ENCAP-TYPE " := "

espinudp " | "

espinudp-nonike ALGO-LIST " := [ " ALGO-LIST " ] | [ " ALGO " ] " ALGO " := " ALGO_TYPE ALGO_NAME ALGO_KEY 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 " ] "

R DIR SELECTOR " [ "

R index INDEX " ] "
" [ " ptype PTYPE " ] " " [ " action ACTION " ] " " [ " priority PRIORITY " ] "
" [ " LIMIT-LIST " ] [ " TMPL-LIST " ] "

R DIR " [ " SELECTOR " | "

R index INDEX " ] "
" [ " ptype PTYPE " ] "

R " [ " 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)

R LISTofOBJECTS " ] "

3. OPTIONS

R

    print the version of the

ip utility and exit.

R

    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.

R

    followed by protocol family identifier:

R 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

R

link is a special family identifier meaning that no networking protocol is involved.

-4

    shortcut for

R

-6

    shortcut for

R

-0

    shortcut for

R

R

    output each record on a single line, replacing line feeds with the

'\\' character. This is convenient when you want to count records with

R wc (1) or to

R grep (1) the output.

R

    use the system's name resolver to print DNS names instead of host addresses.

4. IP - COMMAND SYNTAX

4.1.

OBJECT

link

    - network device.

address

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

addrlabel

    - label configuration for protocol address selection.

neighbour

    - ARP or NDISC cache entry.

route

    - routing table entry.

rule

    - rule in routing policy database.

maddress

    - 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.

4.2.

COMMAND 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

R 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,

R

5. ip link - network device configuration

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

5.1. ip link add - add virtual link

  • link DEVICE
        specifies the physical device to act operate on. NAME specifies the name of the new virtual device. TYPE specifies the type of the new device.

    Link types:

vlan - 802.1q tagged virrtual LAN interface

macvlan - virtual interface base on link layer address (MAC)

can - Controller Area Network interface

5.2. ip link delete - delete virtual link

DEVICE specifies the virtual device to act operate on. TYPE specifies the type of the device.

  • dev DEVICE
        specifies the physical device to act operate on.

5.3. ip link set - change device attributes

  • dev DEVICE
        .I DEVICE specifies network device to operate on. When configuring SR-IOV Virtual Fuction (VF) devices, this keyword should specify the associated Physical Function (PF) device.

R up

    change the state of the device to

UP or

R

R

    change the

NOARP flag on the device.

R

    change the

MULTICAST flag on the device.

R

    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" .
  • 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.

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 disables 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 call.

5.4. ip link show - display device attributes

  • dev NAME (default)
        .I NAME specifies the network device to show. If this argument is omitted all devices are listed.

up

    only display running interfaces.

6. 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.

6.1. 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

R 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.

6.2. 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.

6.3. 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.

R dynamic

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

tentative

    (IPv6 only) only list addresses which have not yet passed duplicate address detection.

deprecated

    (IPv6 only) only list deprecated addresses.

dadfailed

    (IPv6 only) only list addresses which have failed duplicate address detection.

temporary

    (IPv6 only) only list temporary addresses.

R primary

    only list primary (or secondary) addresses.

6.4. 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.

7. 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.

7.1. 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.

7.2. 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 required.

7.3. ip addrlabel list - list address labels

the command show contents of address labels.

7.4. ip addrlabel flush - flush address labels

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

8. 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.

8.1. ip neighbour add - add a new neighbour entry

8.2. ip neighbour change - change an existing entry

8.3. 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

R

  • 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.

8.4. ip neighbour delete - delete a neighbour entry

This command invalidates a neighbour entry.

The arguments are the same as with

R 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.

8.5. 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

R

8.6. 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

R

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.

9. 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 error.

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

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

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

nat - a special NAT route. Destinations covered by the prefix are considered to be dummy (or external) addresses which require translation to real (or internal) ones before forwarding. The addresses to translate to are selected with the attribute

Warning: Route NAT is no longer supported in Linux 2.6.

R

anycast "- " "not implemented" the destinations are anycast addresses assigned to this host. They are mainly equivalent to

local with one difference: such addresses are invalid when used as the source address of any packet.

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

Route tables: Linux-2.x can pack routes into several routing tables identified by a number in the range from 1 to 2^31 or by name from the file

/etc/iproute2/rt_tables By default all normal routes are inserted into the

main table (ID 254) and the kernel only uses this table when calculating routes. Values (0, 253, 254, and 255) are reserved for built-in use.

Actually, one other table always exists, which is invisible but even more important. It is the

local table (ID 255). This table consists of routes for local and broadcast addresses. The kernel maintains this table automatically and the administrator usually need not modify it or even look at it. The multiple routing tables enter the game when policy routing is used.

9.1. ip route add - add new route

9.2. ip route change - change route

9.3. 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

R 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

R

  • 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

R

  • 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

R If this parameter is omitted,

ip assumes the

main table, with the exception of

R local 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

R

  • 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 above.
  • ssthresh NUMBER (2.3.15+ only)
        an estimate for the initial slow start threshold.
  • cwnd NUMBER (2.3.15+ only)
        the clamp for congestion window. It is ignored if the

lock flag is not used.

  • initcwnd NUMBER (2.5.70+ only)
        the initial congestion window size for connections to this destination. Actual window size is this value multiplied by the MSS (``Maximal Segment Size'') for same connection. The default is zero, meaning to use the values specified in RFC2414.
  • initrwnd NUMBER (2.6.33+ only)
        the initial receive window size for connections to this destination. Actual window size is this value multiplied by the MSS of the connection. The default value is zero, meaning to use Slow Start value.
  • 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

R

  • 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

R If this parameter is omitted,

ip assumes scope

global for all gatewayed

unicast routes, scope

link for direct

R unicast routes and scope

R host routes.

  • protocol RTPROTO
        the routing protocol identifier of this route. RTPROTO may be a number or a string from the file

R 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.

9.4. ip route delete - delete route

ip route del has the same arguments as

R 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.

9.5. 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

R table main TABLEID may either be the ID of a real table or one of the special values:

all - list all of the tables.

cache - dump the routing cache.

cloned

cached

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

R

  • from SELECTOR
        the same syntax as for

R 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
  • realms FROMREALM/TOREALM
        only list routes with these realms.

9.6. 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

R 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.

9.7. ip route get - get a single route

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

  • to ADDRESS (default)
        the destination address.
  • from ADDRESS
        the source address.
  • tos TOS
  • dsfield TOS
        the Type Of Service.
  • iif NAME
        the device from which this packet is expected to arrive.
  • oif NAME
        force the output device on which this packet will be routed.

connected

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

Note that this operation is not equivalent to

R

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

R 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.

10. ip rule - routing policy database management

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

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

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

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

Each policy routing rule consists of a

selector and an

action predicate. The RPDB is scanned in 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

R 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.

10.1. ip rule add - insert a new rule

10.2. ip rule delete - delete a rule

  • type TYPE (default)
        the type of this rule. The list of valid types was given in the previous subsection.
  • from PREFIX
        select the source prefix to match.
  • to PREFIX
        select the destination prefix to match.
  • iif NAME
        select the incoming device to match. If the interface is loopback, the rule only matches packets originating from this host. This means that you may create separate routing tables for forwarded and local packets and, hence, completely segregate them.
  • oif NAME
        select the outgoing device to match. The outgoing interface is only available for packets originating from local sockets that are bound to a device.
  • tos TOS
  • dsfield TOS
        select the TOS value to match.
  • fwmark MARK
        select the

fwmark value to match.

  • 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 finishes a batch of updates, it flushes the routing cache with

R

10.3. ip rule flush - also dumps all the deleted rules.

This command has no arguments.

10.4. ip rule show - list rules

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

11. ip maddress - multicast addresses management

maddress objects are multicast addresses.

11.1. ip maddress show - list multicast addresses

  • dev NAME (default)
        the device name.

11.2. ip maddress add - add a multicast address

11.3. 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.

12. 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.

12.1. 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.

13. 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.

13.1. ip tunnel add - add a new tunnel

13.2. ip tunnel change - change an existing tunnel

13.3. 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:

R ipip
Modes for IPv6 encapsulation available:

R ip6ip6

  • 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:

R The default value for IPv6 tunnels is:

R

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

R

  • 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.

nopmtudisc

    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

R ikey parameters set different keys for input and output.

R csum

     ( " 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

R

R seq

     ( " 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

R

It isn't work. Don't use it.

R

     ( " 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.

13.4. 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.

13.5. ip tunnel show - list tunnels

This command has no arguments.

14. 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:

R LISTofOBJECTS " ]" OBJECT-LIST is the list of object types that we want to monitor. It may contain

R link 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

R 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.

15. 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.

15.1. ip xfrm state add - add new state into xfrm

15.2. ip xfrm state update - update existing xfrm state

15.3. ip xfrm state allocspi - allocate SPI value

  • MODE
        is set as default to

R transport but it could be set to

R tunnel

  • FLAG-LIST
        contains one or more flags.
  • FLAG
        could be set to

R noecn

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

R espinudp

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

R enc

15.4. ip xfrm policy add - add a new policy

15.5. ip xfrm policy update - update an existing policy

15.6. ip xfrm policy delete - delete existing policy

15.7. ip xfrm policy get - get existing policy

15.8. ip xfrm policy deleteall - delete all existing xfrm policy

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

15.10. ip xfrm policy flush - flush policies

It can be flush

R all policies or only those specified with

R ptype

  • dir DIR
        directory could be one of these:

R

  • SELECTOR
        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

R sport destination port

R dport 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

R could be switch on

R

  • action ACTION
        is set as default on

R It could be switch on

R

  • priority PRIORITY
        priority is a number. Default priority is set on zero.
  • LIMIT-LIST
        limits are set in seconds, bytes or numbers of packets.
  • TMPL-LIST
        template list is based on ID ","

R mode

  • ID
        is specified by source address, destination address, proto and value of spi "."
  • XFRM_PROTO
        values:

R esp

  • MODE
        is set as default on

R transport but it could be set on

R tunnel

  • LEVEL
        is set as default on

R required and the other choice is

R use

  • UPSPEC
        is specified by

R sport

R dport and

code (NUMBER).

15.11. 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.

16. HISTORY

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

17. SEE ALSO

R tc (8)
"IP Command reference " ip-cref.ps
"IP tunnels " ip-cref.ps
"User documentation at " http://lartc.org/ ", but please direct bugreports and patches to: " < >

18. AUTHOR

Original Manpage by Michail Litvak < >