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_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 ]
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 /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.
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.
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.
low - the route has a lowest priority
medium - the route has a default priority
high - the route has a highest priority
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 packets 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 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.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 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 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 Segments 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 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).
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 configuration 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 ]
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.
all - list all of the tables.
cache - dump the routing cache.
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.
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.
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
ip route add default via 192.168.1.1 dev eth0
ip route add 10.1.1.0/30 encap mpls 200/300 via 10.1.1.1 dev eth0
ip -6 route add 2001:db8:1::/64 encap seg6 mode encap segs 2001:db8:42::1,2001:db8:ffff::2 dev eth0
ip -6 route add 2001:db8:1::/64 encap seg6local action End.DT46 vrftable 100 dev vrf100
ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors next-csid dev eth0
ip -6 route add 2001:db8:1::/64 encap seg6local action End flavors next-csid lblen 48 nflen 16 dev eth0
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
ip route add 10.1.1.0/30 nhid 10
Original Manpage by Michail Litvak <mci@owl.openwall.com>
13 Dec 2012 | iproute2 |