IP(8) Linux IP(8)
NAME
ip - show / manipulate routing, devices, policy routing and tunnels
SYNOPSIS
ip [ OPTIONS ] OBJECT { COMMAND | help }
OBJECT := { link | addr | route | rule | neigh | tunnel | maddr |
mroute | monitor }
OPTIONS := { -V[ersion] | -s[tatistics] | -r[esolve] | -f[amily] { inet
| inet6 | ipx | dnet | link } | -o[neline] }
ip link set DEVICE { up | down | arp { on | off } |
promisc { on | off } |
allmulti { on | off } |
dynamic { on | off } |
multicast { on | off } |
txqueuelen PACKETS |
name NEWNAME |
address LLADDR | broadcast LLADDR |
mtu MTU }
ip link show [ DEVICE ]
ip addr { add | del } IFADDR dev STRING
ip addr { show | flush } [ dev STRING ] [ scope SCOPE-ID ] [ to PREFIX
] [ FLAG-LIST ] [ label PATTERN ]
IFADDR := PREFIX | ADDR peer PREFIX [ broadcast ADDR ] [ anycast ADDR ]
[ label STRING ] [ scope SCOPE-ID ]
SCOPE-ID := [ host | link | global | NUMBER ]
FLAG-LIST := [ FLAG-LIST ] FLAG
FLAG := [ permanent | dynamic | secondary | primary | tentative | dep-
recated ]
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 NUMBER ] [
rttvar NUMBER ] [ window NUMBER ] [ cwnd NUMBER ] [ initcwnd
NUMBER ] [ ssthresh REALM ] [ realms REALM ]
TYPE := [ unicast | local | broadcast | multicast | throw | unreachable
| prohibit | blackhole | nat ]
TABLE_ID := [ local| main | default | all | NUMBER ]
SCOPE := [ host | link | global | NUMBER ]
FLAGS := [ equalize ]
NHFLAGS := [ onlink | pervasive ]
RTPROTO := [ kernel | boot | static | NUMBER ]
ip rule [ list | add | del | 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 }
ip maddr [ add | del ] MULTIADDR dev STRING
ip maddr show [ dev STRING ]
ip mroute show [ PREFIX ] [ from PREFIX ] [ iif DEVICE ]
ip monitor [ all | LISTofOBJECTS ]
OPTIONS
-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(1)
or to grep(1) the output.
-r, -resolve
use the system’s name resolver to print DNS names instead of
host addresses.
IP - COMMAND SYNTAX
OBJECT
link - network device.
address
- protocol (IP or IPv6) address on a device.
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.
The names of all objects may be written in full or abbreviated form,
f.e. address is abbreviated as addr or just a.
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 com-
mands 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 recom-
mended 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 immedi-
ately 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 corre-
sponding 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 num-
ber, 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 pre-
fix.
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 avail-
able 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 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 proper-
ties, 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. 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 val-
ues 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 destina-
tions 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 pack-
ets 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 ENETUN-
REACH 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 forward-
ing. 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 dis-
covery will be tried, all packets will be sent without the DF
bit in IPv4 case or fragmented to MTU for IPv6.
window NUMBER
the maximal window for TCP to advertise to these destinations,
measured in bytes. It limits maximal data bursts that our TCP
peers are allowed to send to us.
rtt NUMBER
the initial RTT (’Round Trip Time’) estimate.
rttvar NUMBER (2.3.15+ only)
the initial RTT variance estimate.
ssthresh NUMBER (2.3.15+ only)
an estimate for the initial slow start threshold.
cwnd NUMBER (2.3.15+ only)
the clamp for congestion window. It is ignored if the lock flag
is not used.
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 destina-
tions 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 multi-
path 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 redi-
rect.
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 proto-
col.
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. With-
out 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 seman-
tics 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. SELEC-
TOR 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 PRE-
FIX. 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 PRE-
FIX.
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 subsec-
tion.
ip route get - get a single route
this command gets a single route to a destination and prints its con-
tents 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 algo-
rithm.
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 ’rout-
ing policy database’ (or RPDB), which selects routes by executing some
set of rules.
Each policy routing rule consists of a selector and an action predi-
cate. 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 pro-
gram 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 ta-
ble containing high priority control routes for local and broad-
cast addresses.
Rule 0 is special. It cannot be deleted or overridden.
2. Priority: 32766, Selector: match anything, Action: lookup rout-
ing 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 rout-
ing 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 loop-
back, the rule only matches packets originating from this host.
This means that you may create separate routing tables for for-
warded 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 rout-
ing 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 pack-
ets. The icsum flag requires that all input packets have the
correct checksum. The csum flag is equivalent to the combina-
tion 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.
HISTORY
ip was written by Alexey N. Kuznetsov and added in Linux 2.2.
SEE ALSO
tc(8)
IP Command reference ip-cref.ps
IP tunnels ip-cref.ps
AUTHOR
Original Manpage by Michail Litvak <mci@owl.openwall.com>
iproute2 17 January 2002 IP(8)
