はじめに
よく忘れるのでメモ。
ip route チートシート
概要
ip route コマンドは、Linux のルーティングテーブルを管理・表示するためのツール。
ルーティングテーブルの表示
現在のmainルーティングテーブルを表示する。
ip route show
show のエイリアスとして、ルートを一覧表示する。
ip route list
全てのテーブルの行を表示するには、table allで全てのテーブルを指定する。
ip route show table all
どの送信パケットに対して、どのテーブルを使うのかは、ip ruleで取り扱うルールで決まる。
詳細は、ip ruleを参照。
テーブルについて
テーブルは、数値のIDで管理され、エイリアス名をつけることもできる。 エイリアスの有無による挙動の差はない。
- テーブルの一覧を得るコマンドはない。
- テーブルIDの番号が小さいほうが優先度が高いなどはない。
- エイリアス名を設定するには、
/etc/iproute2/rt_tablesに書き込む。- ID=200のテーブルにmytableという名前をつける例。
echo "200 mytable" | sudo tee -a /etc/iproute2/rt_tables
- テーブルには、行があるないとは別にテーブルが存在するしないという状態もあるらしい。 実験したところ、一回でも行が存在したテーブルは、存在することになるらしい。
行を足す前(上記コマンドでrt_tablesにID=200のmytableを追加したのみ)
コマンド
ip route show table 200
結果
RTNETLINK answers: Operation not permitted
行を足して消した後
コマンド
ip route show table 200
結果
# エラーなし
- 多くのディストリビューションでは、下記のような設定がデフォルトでされている。
コマンド
cat /etc/iproute2/rt_tables
結果
#
# reserved values
#
255 local
254 main
253 default
0 unspec
#
# local
#
デフォルトゲートウェイの設定
デフォルトゲートウェイを設定する。
ip route add default via <GATEWAY_IP>
デフォルトゲートウェイを削除する。
ip route del default
静的ルートの追加・削除
指定した宛先 (DESTINATION) へのルートを追加する。
ip route add <DESTINATION> via <GATEWAY_IP>
指定した宛先のルートを削除する。
ip route del <DESTINATION>
感想
delはIDや行番号の指定のほうが、便利なときもある気がするが、なさそう。
インターフェース経由のルート設定
特定のネットワークインターフェース (INTERFACE) 経由で宛先に到達するルートを追加する。
ip route add <DESTINATION> dev <INTERFACE>
インターフェース経由のルートを削除する。
ip route del <DESTINATION> dev <INTERFACE>
メトリックを指定したルート設定
メトリック (METRIC) を指定してルートを追加する。
ip route add <DESTINATION> via <GATEWAY_IP> metric <METRIC>
メトリックは、数値が小さいほど優先度が高い。
実験結果
有線LANとWifiをつないだところ、下記のようなmetricであった。
default via 192.168.1.1 dev eth0 proto static metric 100
default via 192.168.1.1 dev wlp2s0 proto static metric 20600
LANの方が優先度が高いことがわかる。 また、metricがない場合は、metric=0として扱われるらしい。
ルーティングキャッシュの管理
キャッシュの表示
ip route show cache
手元だと何も表示されなかった。
ルーティングキャッシュを削除する。 現在では、ルーティングテーブルの更新時に自動で削除されるため、ほぼ不要らしい。
ip route flush cache
マルチパスルーティング
複数のゲートウェイ (GATEWAY1, GATEWAY2) を使用したマルチパスルーティングを設定する。
ip route add <DESTINATION> nexthop via <GATEWAY1> nexthop via <GATEWAY2>
ルートテーブルの指定
特定のルーティングテーブル (TABLE_ID) にルートを追加する。
ip route add <DESTINATION> via <GATEWAY_IP> table <TABLE_ID>
指定したルーティングテーブルの内容を表示する。
ip route show table <TABLE_ID>
よく使うオプション
| 説明 | オプション |
|---|---|
| ルートを表示する | show / list |
| ルートを追加する | add |
| ルートを削除する | del |
| デフォルトゲートウェイを指定する | default |
| ゲートウェイを指定する | via |
| インターフェースを指定する | dev |
| ルートの優先度を設定する | metric |
| 特定のルートテーブルを指定する | table |
| ルートキャッシュを削除する | flush cache |
参考リンク
man ip routeより引用
IP-ROUTE(8) Linux IP-ROUTE(8)
NAME
ip-route - routing table management
SYNOPSIS
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_IOAM6 ]
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 | encap.red | inline | l2encap | l2encap.red ] segs SEGMENTS [ hmac KEYID ]
ENCAP_SEG6LOCAL := seg6local action SEG6_ACTION [ SEG6_ACTION_PARAM ] [ count ]
ENCAP_IOAM6 := ioam6 [ freq K/N ] mode [ inline | encap | auto ] [ tundst ADDRESS ] trace prealloc type IOAM6_TRACE_TYPE ns IOAM6_NAMESPACE
size IOAM6_TRACE_SIZE
ROUTE_GET_FLAGS := [ fibmatch ]
DESCRIPTION
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 pre‐
tending 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 trans‐
lation 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 /etc/iproute2/rt_tables By default all normal routes are inserted into the main table (ID 254) and the kernel only uses this table when
calculating routes. Values (0, 253, 254, and 255) are reserved for built-in use.
Actually, one other table always exists, which is invisible but even more important. It is the local table (ID 255). This table consists of
routes for local and broadcast addresses. The kernel maintains this table automatically and the administrator usually need not modify it or
even look at it.
The multiple routing tables enter the game when policy routing is used.
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. PRE‐
FIX 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, 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 /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.
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 /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 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 en‐
forced/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
/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 un‐
derstand 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 mes‐
sages. 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
ioam6 - encapsulation type IPv6 IOAM
xfrm - encapsulation type XFRM
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 encap.red - Encapsulate packet in an outer IPv6 header with SRH applying the reduced segment list. When there is
only one segment and the HMAC is not present, the SRH is omitted.
mode l2encap - Encapsulate ingress L2 frame within an outer IPv6 header and SRH
mode l2encap.red - Encapsulate ingress L2 frame within an outer IPv6 header and SRH applying the reduced segment list.
When there is only one segment and the HMAC is not present, the SRH is omitted.
SEGMENTS - List of comma-separated IPv6 addresses
KEYID - Numerical value in decimal representation. See ip-sr(8).
seg6local
SEG6_ACTION [ SEG6_ACTION_PARAM ] [ count ] - Operation to perform on matching packets. The optional count attribute
is used to collect statistics on the processing of actions. Three counters are implemented: 1) packets correctly
processed; 2) bytes correctly processed; 3) packets that cause a processing error (i.e., missing SID List, wrong SID
List, etc). To retrieve the counters related to an action use the -s flag in the show command. The following actions
are currently supported (Linux 4.14+ only).
End [ flavors FLAVORS ] - Regular SRv6 processing as intermediate segment endpoint. This action only accepts pack‐
ets with a non-zero Segments Left value. Other matching packets are dropped. The presence of flavors can change the
regular processing of an End behavior according to the user-provided Flavor operations and information carried in
the packet. See Flavors parameters section.
End.X nh6 NEXTHOP - Regular SRv6 processing as intermediate segment endpoint. Additionally, forward processed pack‐
ets 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.DT6 { table | vrftable } TABLEID - Decapsulate the inner IPv6 packet and forward it according to the specified
lookup table. TABLEID is either a number or a string from the file /etc/iproute2/rt_tables. If vrftable is used,
the argument must be a VRF device associated with the table id. Moreover, the VRF table associated with the table id
must be configured with the VRF strict mode turned on (net.vrf.strict_mode=1). 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.DT4 vrftable TABLEID - Decapsulate the inner IPv4 packet and forward it according to the specified lookup table.
TABLEID is either a number or a string from the file /etc/iproute2/rt_tables. The argument must be a VRF device as‐
sociated with the table id. Moreover, the VRF table associated with the table id must be configured with the VRF
strict mode turned on (net.vrf.strict_mode=1). This action only accepts packets with either a zero Segments Left
value or no SRH at all, and an inner IPv4 packet. Other matching packets are dropped.
End.DT46 vrftable TABLEID - Decapsulate the inner IPv4 or IPv6 packet and forward it according to the specified
lookup table. TABLEID is either a number or a string from the file /etc/iproute2/rt_tables. The argument must be a
VRF device associated with the table id. Moreover, the VRF table associated with the table id must be configured
with the VRF strict mode turned on (net.vrf.strict_mode=1). This action only accepts packets with either a zero Seg‐
ments Left value or no SRH at all, and an inner IPv4 or 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 modi‐
fied. 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. Addi‐
tionally, 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).
Flavors parameters
The flavors represent additional operations that can modify or extend a subset of the existing behaviors.
flavors OPERATION[,OPERATION] [ATTRIBUTES]
OPERATION := { psp | usp | usd | next-csid }
ATTRIBUTES := { KEY VALUE } [ ATTRIBUTES ]
KEY := { lblen | nflen }
psp - Penultimate Segment Pop of the SRH (not yet supported in kernel)
usp - Ultimate Segment Pop of the SRH (not yet supported in kernel)
usd - Ultimate Segment Decapsulation (not yet supported in kernel)
next-csid - The NEXT-C-SID mechanism offers the possibility of encoding several SRv6 segments within a single 128
bit SID address. The NEXT-C-SID flavor can be configured to support user-provided Locator-Block and Locator-Node
Function lengths. If Locator-Block and/or Locator-Node Function lengths are not provided by the user during con‐
figuration of an SRv6 End behavior instance with NEXT-C-SID flavor, the default value is 32-bit for Locator-Block
and 16-bit for Locator-Node Function.
lblen VALUE - defines the Locator-Block length for NEXT-C-SID flavor. The Locator-Block length must be greater
than 0 and evenly divisible by 8. This attribute can be used only with NEXT-C-SID flavor.
nflen VALUE - defines the Locator-Node Function length for NEXT-C-SID flavors. The Locator-Node Function length
must be greater than 0 and evenly divisible by 8. This attribute can be used only with NEXT-C-SID flavor.
ioam6
freq K/N - Inject IOAM in K packets every N packets (default is 1/1).
mode inline - Directly insert IOAM after IPv6 header (default mode).
mode encap - Encapsulate packet in an outer IPv6 header with IOAM.
mode auto - Automatically use inline mode for local packets and encap mode for in-transit packets.
tundst ADDRESS - IPv6 address of the tunnel destination (outer header), not used with inline mode.
type IOAM6_TRACE_TYPE - List of IOAM data required in the trace, represented by a bitfield (24 bits).
ns IOAM6_NAMESPACE - Numerical value to represent an IOAM namespace. See ip-ioam(8).
size IOAM6_TRACE_SIZE - Size, in octets, of the pre-allocated trace data block.
xfrm
if_id IF_ID [ link_dev LINK_DEV ]
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 coin‐
cide 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 up‐
dated. 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.
NOTES
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.
EXAMPLES
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 -6 route add 2001:db8:1::/64 encap seg6local action End.DT46 vrftable 100 dev vrf100
Adds an IPv6 route with SRv6 decapsulation and forward with lookup in VRF table.
ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors next-csid dev eth0
Adds an IPv6 route with SRv6 End behavior with next-csid flavor enabled.
ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors next-csid lblen 48 nflen 16 dev eth0
Adds an IPv6 route with SRv6 End behavior with next-csid flavor enabled and user-provided Locator-Block and Locator-Node Function lengths.
ip -6 route add 2001:db8:1::/64 encap ioam6 freq 2/5 mode encap tundst 2001:db8:42::1 trace prealloc type 0x800000 ns 1 size 12 dev eth0
Adds an IPv6 route with an IOAM Pre-allocated Trace encapsulation (ip6ip6) that only includes the hop limit and the node id, configured
for the IOAM namespace 1 and a pre-allocated data block of 12 octets (will be injected in 2 packets every 5 packets).
ip route add 10.1.1.0/30 nhid 10
Adds an ipv4 route using nexthop object with id 10.
SEE ALSO
ip(8)
AUTHOR
Original Manpage by Michail Litvak <[email protected]>
iproute2 13 Dec 2012 IP-ROUTE(8)