Linux and Unix ip command
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Show and manipulate routing, devices, policy routing and tunnels.
Synopsis
Options
IP - Command Syntax
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 } | allmulti { on | off
} | dynamic { on | off } | multicast { on | off } | txqueuelen PACKETS |
name NEWNAME | address LLADDR | broadcast LLADDR | mtu MTU }
ip link
show [ DEVICE ]
ip addr { add | del } IFADDR dev STRING
ip
addr { show | flush } [ dev STRING ] [ scope SCOPE-ID ] [ to PREFIX ] [
FLAG-LIST ] [ label PATTERN ]
IFADDR := PREFIX | ADDR peer PREFIX [
broadcast ADDR ] [ anycast ADDR ] [ label STRING ] [ scope SCOPE-ID ]
SCOPE-ID := [ host | link | global | NUMBER ]
FLAG-LIST := [
FLAG-LIST ] FLAG
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 ]
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 ] [ initcwnd NUMBER ]
[ ssthresh REALM ] [ realms REALM ] [ rto_min TIME ]
TYPE := [
unicast | local | broadcast | multicast | throw | unreachable | prohibit |
blackhole | nat ] 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 ] [ dev STRING ] [
pref NUMBER ]
ACTION := [ table TABLE_ID ] [ nat ADDRESS ] [ prohibit
| reject | unreachable ] [ realms [SRCREALM/]DSTREALM ]
TABLE_ID := [
local | main | default | NUMBER ]
ip neigh { add | del | change |
replace } { ADDR [ lladdr LLADDR ] [ nud { permanent | noarp | stale |
reachable } ] | proxy ADDR } [ dev DEV ]
ip neigh { show | flush } [
to PREFIX ] [ dev DEV ] [ nud STATE ]
ip tunnel { add | change | del
| show } [ NAME ] [ mode { ipip | gre | sit } ] [ remote ADDR ] [ local ADDR
] [ [i|o]seq ] [ [i|o]key KEY ] [ [i|o]csum ] ] [ ttl TTL ] [ tos TOS ] [
[no]pmtudisc ] [ dev PHYS_DEV ]
ADDR := { IP_ADDRESS | any }
TOS := { NUMBER | inherit }
TTL := { 1..255 | inherit }
KEY :=
{ DOTTED_QUAD | NUMBER }
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 ]
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 ]
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 ]
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 ]
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 ]
LEVEL := [ required | use ]
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 networking protocol is involved. |
| -4 | Shortcut for -family inet. |
| -6 | Shortcut for -family inet6. |
| -0 | Shortcut for -family link. |
| -o, -oneline | Output each record on a single line, replacing line feeds with the '"' character. This is convenient when you want to count records with wc or to grep the output. |
| -r, -resolve | Use the system's name resolver to print DNS names instead of host addresses. |
OBJECT
The names of all objects may be written in full or abbreviated form, f.e. address is abbreviated as addr or just a.
| 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. |
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 add, delete and show (or list ) objects, but some objects do not allow all of these operations or have some additional commands. The help command is available for all objects. It prints out a list of available commands and argument syntax conventions.
If no command is given, some default command is assumed. Usually it is list or, if the objects of this class cannot be listed, help.
ip link - network device configuration
link is a network device
and the corresponding commands display and change the state of devices.
ip link set - change device attributes
dev NAME (default)
NAME specifies network device to operate on.
up and down
change the state of the device to UP or DOWN.
arp on or arp off
change the NOARP flag on the device.
multicast on or multicast off
change the MULTICAST flag on the device.
dynamic on or dynamic off
change the DYNAMIC flag on the device.
name NAME
change the
name of the device. This operation is not recommended if the device is
running or has some addresses already configured.
txqueuelen
NUMBER
txqlen NUMBER
change the transmit queue length
of the device.
mtu NUMBER
change the MTU of the device.
address LLADDRESS
change the station address of the interface.
broadcast LLADDRESS
brd LLADDRESS
peer
LLADDRESS
change the link layer broadcast address or the peer address
when the interface is POINTOPOINT.
Warning: If multiple
parameter changes are requested, ip aborts immediately after any of the
changes have failed. This is the only case when ip can move the system to an
unpredictable state. The solution is to avoid changing several parameters
with one ip link set call.
ip link show - display device
attributes
dev NAME (default)
NAME specifies the network
device to show. If this argument is omitted all devices are listed.
up only display running interfaces.
ip address - protocol
address management.
The address is a protocol (IP or IPv6)
address attached to a network device. Each device must have at least one
address to use the corresponding protocol. It is possible to have several
different addresses attached to one device. These addresses are not
discriminated, so that the term alias is not quite appropriate for
them and we do not use it in this document.
The ip addr
command displays addresses and their properties, adds new addresses and
deletes old ones.
ip address add - add new protocol address.
dev NAME
the name of the device to add the address to.
local ADDRESS (default)
the address of the interface. The format of
the address depends on the protocol. It is a dotted quad for IP and a
sequence of hexadecimal halfwords separated by colons for
IPv6. The
ADDRESS may be followed by a slash and a decimal number which encodes the
network prefix length.
peer ADDRESS
the address of the
remote endpoint for pointopoint interfaces. Again, the ADDRESS may be
followed by a slash and a decimal number, encoding the network prefix
length. If
a peer address is specified, the local address cannot have a
prefix length. The network prefix is associated with the peer rather than
with the local address.
broadcast ADDRESS
the broadcast
address on the interface.
It is possible to use the special symbols
'+' 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. Predefined scope values are:
global - the address is globally valid.
site
- (IPv6 only) the address is site local, i.e. it is valid inside this site.
link - the address is link local, i.e. it is valid only on this
device.
host - the address is valid only inside this host.
ip address delete - delete protocol address
Arguments: coincide
with the arguments of ip addr add. The device name is a required argument.
The rest are optional. If no arguments are given, the first address is
deleted.
ip address show - look at protocol addresses
dev
NAME (default)
name of device.
scope SCOPE_VAL
only list
addresses with this scope.
to PREFIX
only list addresses
matching this prefix.
label PATTERN
only list addresses
with labels matching the PATTERN. PATTERN is a usual shell style pattern.
dynamic and permanent
(IPv6 only) only list addresses
installed due to stateless address configuration or only list permanent (not
dynamic) addresses.
tentative
(IPv6 only) only list
addresses which did not pass duplicate address detection.
deprecated
(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 required.
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 'Neighbour Unreachability Detection'. The state
can take one of the following values:
permanent - the neighbour entry is valid forever and
can be only be removed administratively.
noarp - the neighbour
entry is valid. No attempts to validate this entry will be made but it can
be removed when its lifetime expires.
reachable - the
neighbour entry is valid until the reachability timeout expires.
stale - the neighbour entry is valid but suspicious. This option to ip
neigh does not change the neighbour state if it was valid and the address is
not changed by this command.
ip neighbour delete - delete a neighbour entry
This command
invalidates a neighbour entry.
The arguments are the same as with ip
neigh add, except that lladdr and nud are ignored.
Warning:
Attempts to delete or manually change a noarp entry created by the kernel
may result in unpredictable behaviour. Particularly, the kernel may try to
resolve this address even on a NOARP interface or if the address is
multicast or broadcast.
ip neighbour show - list neighbour entries
This commands displays neighbour tables.
to ADDRESS (default)
the prefix selecting the
neighbours to list.
dev NAME
only list the neighbours
attached to this device.
unused only list neighbours which are
not currently in use.
nud NUD_STATE
only list neighbour
entries in this state. NUD_STATE takes values listed below or the special
value all which means all states. This option may occur more than once. If
this option is absent, ip lists all entries except for none and noarp.
ip neighbour flush - flush neighbour entries
This command
flushes neighbour tables, selecting entries to flush by some criteria.
This command has the same arguments as show. The differences are that it
does not run when no arguments are given, and that the default neighbour
states to be flushed do not include permanent and noarp.
With the -statistics option, the command becomes verbose. It
prints out the number of deleted neighbours and the number of rounds made to
flush the neighbour table. If the
option is given twice, ip neigh
flush also dumps all the deleted neighbours.
ip route -
routing table management
Manipulate route entries in the kernel
routing tables keep information about paths to other networked nodes.
Route types:
unicast - the route entry describes real paths to the
destinations covered by the route prefix.
unreachable - these
destinations are unreachable. Packets are discarded and the ICMP message
host unreachable is generated. The local senders get an EHOSTUNREACH error.
blackhole - these destinations are unreachable. Packets are
discarded silently. The local senders get an EINVAL error.
prohibit - these destinations are unreachable. Packets are discarded and
the ICMP message communication administratively prohibited is generated. The
local senders get
an EACCES 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.
via.
anycast - not implemented the destinations are
anycast addresses assigned to this host. They are mainly equivalent to local
with one difference: such addresses are invalid when used as the source
address of any packet.
multicast - a special type used for
multicast routing. It is not present in normal routing tables.
Route tables: Linux-2.x can pack routes into several routing
tables identified by a number in the range from 1 to 255 or by name from the
file /etc/iproute2/rt_tables main table (ID 254) and the kernel only uses
this table when calculating routes.
Actually, one other table always
exists, which is invisible but even more important. It is the local table
(ID 255). This table consists of routes for local and broadcast
addresses. The kernel maintains this table automatically and the
administrator usually need not modify it or even look at it.
The
multiple routing tables enter the game when policy routing is used.
ip route add - add new route
ip route change - change route
ip
route replace - change or add new one
to TYPE PREFIX (default)
the destination prefix of the
route. If TYPE is omitted, ip assumes type unicast. Other values of TYPE are
listed above. PREFIX is an IP or IPv6 address optionally followed by a slash
and the prefix length. If the length of the prefix is missing, ip assumes a
full-length host route. There is also a special PREFIX default - which is
equivalent to IP 0/0 or to IPv6 ::/0.
tos TOS
dsfield TOS
the Type Of Service (TOS) key. This key has no associated
mask and the longest match is understood as: First, compare the TOS of the
route and of the packet. If they are not equal, then the packet may still
match a route with a zero TOS. TOS is either an 8 bit hexadecimal number or
an identifier from /etc/iproute2/rt_dsfield.
metric NUMBER
preference NUMBER
the preference value of the route. NUMBER is
an arbitrary 32bit number.
table TABLEID
the table to add
this route to. TABLEID may be a number or a string from the file
/etc/iproute2/rt_tables. If this parameter is omitted, ip assumes the main
table, with the exception of local , broadcast and nat routes, which are put
into the local table by default.
dev NAME
the output device
name.
via ADDRESS
the address of the nexthop router.
Actually, the sense of this field depends on the route type. For normal
unicast routes it is either the true next hop router or, if it is a direct
route installed in BSD compatibility mode, it can be a local address of the
interface. For NAT routes it is the first address of the block of translated
IP destinations.
src ADDRESS
the source address to prefer
when sending to the destinations covered by the route prefix.
realm REALMID
the realm to which this route is assigned. REALMID may
be a number or a string from the file /etc/iproute2/rt_realms.
mtu
MTU
mtu lock MTU
the MTU along the path to the destination.
If the modifier lock is not used, the MTU may be updated by the kernel due
to Path MTU Discovery. If the modifier lock is used, no path MTU discovery
will be tried, all packets will be sent without the DF bit in IPv4 case or
fragmented to MTU for IPv6.
window NUMBER
the maximal
window for TCP to advertise to these destinations, measured in bytes. It
limits maximal data bursts that our TCP peers are allowed to send to us.
rtt TIME the initial RTT ('Round Trip Time') estimate. If no
suffix is specified the units are raw values passed directly to the routing
code to maintain compatibility with previous releases. Otherwise if a suffix
of s, sec or secs is used to specify seconds; 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
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 net/ipv4/tcp_reordering.
nexthop NEXTHOP
the nexthop of a multipath route. NEXTHOP is a
complex value with its own syntax similar to the top level argument lists:
via 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.
equalize
allow packet by packet
randomization on multipath routes. Without this modifier, the route will be
frozen to one selected nexthop, so that load splitting will only occur on
per-flow base. equalize only works if the kernel is patched.
ip
route delete - delete route
ip route del has the same arguments as ip
route add, but their semantics are a bit different.
Key values (to,
tos, preference and table) select the route to delete.
If optional attributes are present, ip verifies that they coincide with the
attributes of the route to delete. If no route with the given key and
attributes was found, ip route del fails.
ip route show -
list routes
the command displays the contents of the routing tables
or the route(s) selected by some criteria.
to SELECTOR
(default)
only select routes from the given range of destinations.
SELECTOR consists of an optional modifier (root, match or exact) and a
prefix. root PREFIX selects routes with prefixes not shorter than PREFIX.
F.e. root 0/0 selects the entire routing table. match PREFIX selects routes
with prefixes not longer than PREFIX. F.e. match 10.0/16 selects 10.0/16,
10/8 and 0/0, but it does not select 10.1/16 and 10.0.0/24. And exact PREFIX
(or just PREFIX) selects routes with this exact prefix. If neither of these
options are present, ip assumes root 0/0 i.e. it lists the entire table.
tos TOS
dsfield TOS only select routes with the given TOS.
table TABLEID
show the routes from this table(s). The default
setting is to show tablemain. TABLEID may either be the ID of a real table
or one of the special values:
all - list all of the tables.
cache -
dump the routing cache.
cloned
cached list cloned routes i.e. routes which
were dynamically forked from other routes because some route attribute (f.e.
MTU) was updated. Actually, it is equivalent to table cache.
from SELECTOR
the same syntax as for to, but it binds the source
address range rather than destinations. Note that the from option only works
with cloned routes.
protocol RTPROTO
only list routes of
this protocol.
scope SCOPE_VAL
only list routes with this
scope.
type TYPE
only list routes of this type.
dev NAME
only list routes going via this device.
via
PREFIX
only list routes going via the nexthop routers selected by PREFIX.
src PREFIX
only list routes with preferred source addresses
selected by PREFIX.
realm REALMID
realms
FROMREALM/TOREALM
only list routes with these realms.
ip route
flush - flush routing tables
this command flushes routes selected by
some criteria.
The arguments have the same syntax and semantics as
the arguments of ip route show, but routing tables are not listed but
purged. The only difference is the default action: show dumps all the
IP main routing table but flush prints the helper page.
With
the -statistics option, the command becomes verbose. It prints out
the number of deleted routes and the number of rounds made to flush the
routing table. If the option is given twice, ip route flush also
dumps all the deleted routes in the format described in the previous
subsection.
ip route get - get a single route
this command
gets a single route to a destination and prints its contents exactly as the
kernel sees it.
to ADDRESS (default)
the destination
address.
from ADDRESS
the source address.
tos
TOS
dsfield TOS
the Type Of Service.
iif NAME
the device from which this packet is expected to arrive.
oif
NAME
force the output device on which this packet will be routed.
connected
if no source address (option from) was given, relookup
the route with the source set to the preferred address received from the
first lookup. If policy routing is used, it may be a different route.
Note that this operation is not equivalent to ip route show.
show shows existing routes. get resolves them and creates new clones if
necessary. Essentially, get is equivalent to sending a packet along
this path. If the iif argument is not given, the kernel creates a
route to output packets towards the requested destination. This is
equivalent to pinging the destination with a subsequent ip route ls cache,
however, no packets are actually sent. With the iif argument, the kernel
pretends that a packet arrived from this interface and searches for a path
to forward the packet.
ip 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 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
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.
table
TABLEID
the routing table identifier to lookup if the rule selector
matches.
realms FROM/TO
Realms to select if the rule
matched and the routing table lookup succeeded. Realm TO is only used if the
route did not select any realm.
nat ADDRESS
The base of the
IP address block to translate (for source addresses). The ADDRESS may be
either the start of the block of NAT addresses (selected by NAT routes) or a
local host address (or even zero). In the last case the router does not
translate the packets, but masquerades them to this address.
Warning: Changes to the RPDB made with these commands do not become
active immediately. It is assumed that after a script finishes a batch of
updates, it flushes the routing cache with ip route flush cache.
ip rule flush - also dumps all the deleted rules.
This command has no
arguments.
ip rule show - list rules
This command has no
arguments.
ip maddress - multicast addresses management
maddress objects are multicast addresses.
ip maddress show -
list multicast addresses
dev NAME (default)
the
device name.
ip maddress add - add a multicast address
ip
maddress delete - delete a multicast address
these commands
attach/detach a static link layer multicast address to listen on the
interface. Note that it is impossible to join protocol multicast groups
statically. This command only manages link layer 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 administratively, so we may only display them. This
limitation will be removed in the future.
ip mroute show - list
mroute cache entries
to PREFIX (default)
the prefix
selecting the destination multicast addresses to 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 IPv4 packets and then sending
them over the IP infrastructure.
ip tunnel add - add a new tunnel
ip tunnel change - change an existing tunnel
ip tunnel delete - destroy a
tunnel
name NAME (default)
select the tunnel device
name.
mode MODE
set the tunnel mode. Three modes are
currently available: ipip, sit and gre.
remote ADDRESS
set
the remote endpoint of the tunnel.
local ADDRESS
set the
fixed local address for tunneled packets. It must be an address on another
interface of this host.
ttl N set a fixed TTL N on tunneled
packets. N is a number in the range 1--255. 0 is a special value meaning
that packets inherit the TTL value. The default value is: inherit.
tos T
dsfield T
set a fixed TOS T on tunneled
packets. The default value is: 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.
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 ikey and okey parameters set different keys for input
and output.
csum, icsum, ocsum
( only GRE tunnels )
generate/require checksums for tunneled packets. The ocsum flag calculates
checksums for outgoing packets. The icsum flag requires that all input
packets have the correct checksum. The csum flag is equivalent to the
combination icsum ocsum.
seq, iseq, oseq
( only GRE
tunnels ) serialize packets. The oseq flag enables sequencing of
outgoing packets. The iseq flag requires that all input packets are
serialized. The seq flag is equivalent to the combination iseq oseq. It
isn't work. Don't use it.
ip tunnel show - list tunnels
This command has no arguments.
ip monitor and rtmon - state
monitoring
The ip utility can monitor the state of devices, addresses
and routes continuously. This option has a slightly different format.
Namely, the monitor command is the first in the command line and then the
object list follows:
ip monitor [ all | LISTofOBJECTS ]
OBJECT-LIST is the list of object types that we want to monitor. It may
contain link, address and route. If no file argument is
given, ip opens RTNETLINK, listens on it and dumps state changes in the
format described in previous sections.
If a file name is given, it
does not listen on RTNETLINK, but opens the file containing RTNETLINK
messages saved in binary format and dumps them. Such a history file can be
generated with the rtmon utility. This utility has a command line syntax
similar to ip monitor. Ideally, rtmon should be started before the first
network configuration command is issued. F.e. if you insert:
rtmon file /var/log/rtmon.log
in a startup script, you will be able to view the full history later.
Certainly, it is possible to start rtmon at any time. It prepends the
history with the state snapshot dumped at the moment of starting.
ip 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.
FLAG-LIST
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.
ENCAP-TYPE
could be set to espinudp or
espinudp-nonike.
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 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.
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 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.
LIMIT-LIST
limits are
set in seconds, bytes or numbers of packets.
TMPL-LIST
template
list is based on ID, mode, reqid and level.
ID
is specified by source address, destination address, proto and value of spi.
XFRM_PROTO
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.
Tip: You must have root access to use the ip command.
ip link show
Lists the currently installed networking interfaces. Similar to the below output.
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
link/loopback
00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0:
<BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:12:34:56:78:90 brd ff:ff:ff:ff:ff:ff
3: eth1:
<BROADCAST,MULTICAST> mtu 1500 qdisc noop qlen 1000
link/ether
00:12:34:56:67:90 brd ff:ff:ff:ff:ff:ff
ip addr show
Lists the network interfaces.
ip route show
Lists the routing table.