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NAME | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | COLOPHON |
IP-ROUTE(8) Linux IP-ROUTE(8)
ip-route - routing table management
ip [ ip-OPTIONS ] route { COMMAND | help }
ip route { show | flush } SELECTOR
ip route save SELECTOR
ip route restore
ip route get ROUTE_GET_FLAGS ADDRESS [ from ADDRESS iif STRING ] [
oif STRING ] [ mark MARK ] [ tos TOS ] [ vrf NAME ] [ ipproto
PROTOCOL ] [ sport NUMBER ] [ dport NUMBER ]
ip route { add | del | change | append | replace } ROUTE
SELECTOR := [ root PREFIX ] [ match PREFIX ] [ exact PREFIX ] [ table
TABLE_ID ] [ vrf NAME ] [ 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 ] [ ttl-propagate {
enabled | disabled } ]
INFO_SPEC := { NH | nhid ID } OPTIONS FLAGS [ nexthop NH ] ...
NH := [ encap ENCAP ] [ via [ FAMILY ] ADDRESS ] [ dev STRING ] [
weight NUMBER ] NHFLAGS
FAMILY := [ inet | inet6 | mpls | bridge | link ]
OPTIONS := FLAGS [ mtu NUMBER ] [ advmss NUMBER ] [ as [ to ] ADDRESS
] rtt TIME ] [ rttvar TIME ] [ reordering NUMBER ] [ window
NUMBER ] [ cwnd NUMBER ] [ ssthresh NUMBER ] [ realms REALM ]
[ rto_min TIME ] [ initcwnd NUMBER ] [ initrwnd NUMBER ] [
features FEATURES ] [ quickack BOOL ] [ congctl NAME ] [ pref
PREF ] [ expires TIME ] [ fastopen_no_cookie BOOL ]
TYPE := [ unicast | local | broadcast | multicast | throw |
unreachable | prohibit | blackhole | nat ]
TABLE_ID := [ local| main | default | all | NUMBER ]
SCOPE := [ host | link | global | NUMBER ]
NHFLAGS := [ onlink | pervasive ]
RTPROTO := [ kernel | boot | static | NUMBER ]
FEATURES := [ ecn | ]
PREF := [ low | medium | high ]
ENCAP := [ ENCAP_MPLS | ENCAP_IP | ENCAP_BPF | ENCAP_SEG6 |
ENCAP_SEG6LOCAL ]
ENCAP_MPLS := mpls [ LABEL ] [ ttl TTL ]
ENCAP_IP := ip id TUNNEL_ID dst REMOTE_IP [ src SRC ] [ tos TOS ] [
ttl TTL ]
ENCAP_BPF := bpf [ in PROG ] [ out PROG ] [ xmit PROG ] [ headroom
SIZE ]
ENCAP_SEG6 := seg6 mode [ encap | inline | l2encap ] segs SEGMENTS [
hmac KEYID ]
ENCAP_SEG6LOCAL := seg6local action SEG6_ACTION [ SEG6_ACTION_PARAM ]
ROUTE_GET_FLAGS := [ fibmatch ]
ip route is used to manipulate entries in the kernel routing tables.
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 via. Warning: Route NAT is no longer supported
in Linux 2.6.
anycast - not implemented the destinations are anycast
addresses assigned to this host. They are mainly equivalent
to local with one difference: such addresses are invalid when
used as the source address of any packet.
multicast - a special type used for multicast routing. It is
not present in normal routing tables.
Route tables: Linux-2.x can pack routes into several routing tables
identified by a number in the range from 1 to 2^32-1 or by name from
the file /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.
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 /rt_dsfield.
metric NUMBER
preference NUMBER
the preference value of the route. NUMBER is an
arbitrary 32bit number, where routes with lower values
are preferred.
table TABLEID
the table to add this route to. TABLEID may be a
number or a string from the file /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.
vrf NAME
the vrf name to add this route to. Implicitly means the
table associated with the VRF.
dev NAME
the output device name.
via [ FAMILY ] ADDRESS
the address of the nexthop router, in the address
family FAMILY. 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 /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 and ms, msec or
msecs to specify milliseconds.
rttvar TIME (Linux 2.3.15+ only)
the initial RTT variance estimate. Values are specified
as with rtt above.
rto_min TIME (Linux 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 (Linux 2.3.15+ only)
an estimate for the initial slow start threshold.
cwnd NUMBER (Linux 2.3.15+ only)
the clamp for congestion window. It is ignored if the
lock flag is not used.
initcwnd NUMBER (Linux 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 (Linux 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.
features FEATURES (Linux3.18+only)
Enable or disable per-route features. Only available
feature at this time is ecn to enable explicit
congestion notification when initiating connections to
the given destination network. When responding to a
connection request from the given network, ecn will
also be used even if the net.ipv4.tcp_ecn sysctl is set
to 0.
quickack BOOL (Linux 3.11+ only)
Enable or disable quick ack for connections to this
destination.
fastopen_no_cookie BOOL (Linux 4.15+ only)
Enable TCP Fastopen without a cookie for connections to
this destination.
congctl NAME (Linux 3.20+ only)
congctl lock NAME (Linux 3.20+ only)
Sets a specific TCP congestion control algorithm only
for a given destination. If not specified, Linux keeps
the current global default TCP congestion control
algorithm, or the one set from the application. If the
modifier lock is not used, an application may
nevertheless overwrite the suggested congestion control
algorithm for that destination. If the modifier lock is
used, then an application is not allowed to overwrite
the specified congestion control algorithm for that
destination, thus it will be enforced/guaranteed to use
the proposed algorithm.
advmss NUMBER (Linux 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 (Linux 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 [ FAMILY ] 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.
The internal buffer used in iproute2 limits the maximum
number of nexthops that may be specified in one go. If
only ADDRESS is given, the current buffer size allows
for 144 IPv6 nexthops and 253 IPv4 ones. For IPv4, this
effectively limits the number of nexthops possible per
route. With IPv6, further nexthops may be appended to
the same route via ip route append command.
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 /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 /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.
pref PREF
the IPv6 route preference. PREF is a string specifying
the route preference as defined in RFC4191 for Router
Discovery messages. Namely:
low - the route has a lowest priority
medium - the route has a default priority
high - the route has a highest priority
nhid ID
use nexthop object with given id as nexthop
specification.
encap ENCAPTYPE ENCAPHDR
attach tunnel encapsulation attributes to this route.
ENCAPTYPE is a string specifying the supported
encapsulation type. Namely:
mpls - encapsulation type MPLS
ip - IP encapsulation (Geneve, GRE, VXLAN, ...)
bpf - Execution of BPF program
seg6 - encapsulation type IPv6 Segment Routing
seg6local - local SRv6 segment processing
ENCAPHDR is a set of encapsulation attributes specific
to the ENCAPTYPE.
mpls
MPLSLABEL - mpls label stack with labels
separated by /
ttl TTL - TTL to use for MPLS header or 0 to
inherit from IP header
ip
id TUNNEL_ID dst REMOTE_IP [ src SRC ] [ tos
TOS ] [ ttl TTL ] [ key ] [ csum ] [ seq ]
bpf
in PROG - BPF program to execute for incoming
packets
out PROG - BPF program to execute for
outgoing packets
xmit PROG - BPF program to execute for
transmitted packets
headroom SIZE - Size of header BPF program
will attach (xmit)
seg6
mode inline - Directly insert Segment Routing
Header after IPv6 header
mode encap - Encapsulate packet in an outer
IPv6 header with SRH
mode l2encap - Encapsulate ingress L2 frame
within an outer IPv6 header and SRH
SEGMENTS - List of comma-separated IPv6
addresses
KEYID - Numerical value in decimal
representation. See ip-sr(8).
seg6local
SEG6_ACTION [ SEG6_ACTION_PARAM ] - Operation
to perform on matching packets. The
following actions are currently supported
(Linux 4.14+ only).
End - Regular SRv6 processing as
intermediate segment endpoint. This action
only accepts packets with a non-zero
Segments Left value. Other matching packets
are dropped.
End.X nh6 NEXTHOP - Regular SRv6 processing
as intermediate segment endpoint.
Additionally, forward processed packets to
given next-hop. This action only accepts
packets with a non-zero Segments Left
value. Other matching packets are dropped.
End.DX6 nh6 NEXTHOP - Decapsulate inner
IPv6 packet and forward it to the specified
next-hop. If the argument is set to ::,
then the next-hop is selected according to
the local selection rules. This action only
accepts packets with either a zero Segments
Left value or no SRH at all, and an inner
IPv6 packet. Other matching packets are
dropped.
End.B6 srh segs SEGMENTS [ hmac KEYID ] -
Insert the specified SRH immediately after
the IPv6 header, update the DA with the
first segment of the newly inserted SRH,
then forward the resulting packet. The
original SRH is not modified. This action
only accepts packets with a non-zero
Segments Left value. Other matching packets
are dropped.
End.B6.Encaps srh segs SEGMENTS [ hmac
KEYID ] - Regular SRv6 processing as
intermediate segment endpoint.
Additionally, encapsulate the matching
packet within an outer IPv6 header followed
by the specified SRH. The destination
address of the outer IPv6 header is set to
the first segment of the new SRH. The
source address is set as described in
ip-sr(8).
expires TIME (Linux 4.4+ only)
the route will be deleted after the expires time. Only
support IPv6 at present.
ttl-propagate { enabled | disabled }
Control whether TTL should be propagated from any encap
into the un-encapsulated packet, overriding any global
configuration. Only supported for MPLS at present.
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 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.
vrf NAME
show the routes for the table associated with the vrf
name
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 [ FAMILY ] 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.
fibmatch
Return full fib lookup matched route. Default is to
return the resolved dst entry
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.
mark MARK
the firewall mark (fwmark)
vrf NAME
force the vrf device on which this packet will be
routed.
ipproto PROTOCOL
ip protocol as seen by the route lookup
sport NUMBER
source port as seen by the route lookup
dport NUMBER
destination port as seen by the route lookup
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 route save
save routing table information to stdout
This command behaves like ip route show except that the output
is raw data suitable for passing to ip route restore.
ip route restore
restore routing table information from stdin
This command expects to read a data stream as returned from ip
route save. It will attempt to restore the routing table
information exactly as it was at the time of the save, so any
translation of information in the stream (such as device
indexes) must be done first. Any existing routes are left
unchanged. Any routes specified in the data stream that
already exist in the table will be ignored.
Starting with Linux kernel version 3.6, there is no routing cache for
IPv4 anymore. Hence ip route show cached will never print any entries
on systems with this or newer kernel versions.
ip ro
Show all route entries in the kernel.
ip route add default via 192.168.1.1 dev eth0
Adds a default route (for all addresses) via the local gateway
192.168.1.1 that can be reached on device eth0.
ip route add 10.1.1.0/30 encap mpls 200/300 via 10.1.1.1 dev eth0
Adds an ipv4 route with mpls encapsulation attributes attached to
it.
ip -6 route add 2001:db8:1::/64 encap seg6 mode encap segs
2001:db8:42::1,2001:db8:ffff::2 dev eth0
Adds an IPv6 route with SRv6 encapsulation and two segments
attached.
ip route add 10.1.1.0/30 nhid 10
Adds an ipv4 route using nexthop object with id 10.
ip(8)
Original Manpage by Michail Litvak <mci@owl.openwall.com>
This page is part of the iproute2 (utilities for controlling TCP/IP
networking and traffic) project. Information about the project can
be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
netdev@vger.kernel.org, shemminger@osdl.org. This page was obtained
from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-06-24.) If you discover any
rendering problems in this HTML version of the page, or you believe
there is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
iproute2 13 Dec 2012 IP-ROUTE(8)
Pages that refer to this page: ip(8) , ip-sr(8) , ip-vrf(8) , tc-route(8) , wg(8) , wg-quick(8)