ROUTE(8) System Manager's Manual ROUTE(8)
route - manually manipulate the routing tables
route [-dnqtv] [-T tableid] command [[modifiers] args]
route is a utility used to manually view and manipulate the network
routing tables. Except for setting up the default route, it normally is
not needed to manipulate routes, as a system routing table management
daemon, such as ripd(8), ospfd(8), or bgpd(8), should tend to this task.
route can be used to modify nearly any aspect of the routing policy,
except packet forwarding, which can be manipulated through the sysctl(8)
The route utility supports a limited number of general options, but a
rich command language enables the user to specify any arbitrary request
that could be delivered via the programmatic interface discussed in
The options are as follows:
-d Run in debug-only mode, i.e., don't actually modify the routing
-n Bypass attempts to print host and network names symbolically when
reporting actions. (The process of translating between symbolic
names and numerical equivalents can be quite time consuming, and
may require correct operation of the network; thus it may be
expedient to forgo this, especially when attempting to repair
-q Suppress all output.
Select an alternate routing table to modify or query. The
default is to use the current routing table.
-t Write routing messages to a fake device (/dev/null) instead of a
real routing socket to test route manipulation.
-v (verbose) Print additional details.
The route utility provides the following simple commands:
route [-T tableid] exec [command ...]
Execute a command forcing the process and its children to use
the routing table and appropriate routing domain as specified
with the -T tableid option.
route [-nqv] [-T tableid] flush [modifiers]
Delete all gateway entries from the routing table. When the
address family is specified by any one of the family
modifiers (listed below), only routes having destinations
with addresses in the delineated family will be deleted.
Also, only routes matching a specific interface or priority
can be flushed by using the -iface or -priority modifiers.
route [-nv] [-T tableid] get [modifiers] address
Extract a routing entry from the kernel. If -gateway is
specified, only routes whose gateway are in the same address
family as the destination are shown.
route [-n] monitor [modifiers]
Continuously report any changes to the routing information
base, routing lookup misses, or suspected network
When the address family is specified by any one of the family
modifiers (listed below), only routes having destinations
with addresses in the delineated family will be shown. If
the -iface modifier is used only interface specific messages
(link state changes) are shown.
route [-nv] [-T tableid] show [family] [-gateway] [-label label]
Print out the route table similar to "netstat -r" (see
If -gateway is specified, only routes whose gateway are in
the same address family as the destination are shown.
If -label is specified, only routes with the specified label
If -priority is specified, only routes with the specified
(numeric) priority are shown. Some well known priorities can
be given by name. If the priority is negative, then routes
that do not match the numeric priority are shown.
The other commands relating to adding, changing, or deleting routes have
route [-dnqtv] [-T tableid] add [modifiers] destination gateway
route [-dnqtv] [-T tableid] change [modifiers] destination gateway
route [-dnqtv] [-T tableid] delete [modifiers] destination gateway
destination is the destination host or network; gateway is the next-hop
intermediary via which packets should be routed. Routes to a particular
host may be distinguished from those to a network by interpreting the
Internet address specified as the destination argument. The optional
modifiers -net and -host cause the destination to be interpreted as a
network or a host, respectively. Otherwise, type is chosen based on the
The route is assumed to be to a network if any of the following apply to
o it is the word "default", equivalent to 0/0
o it is an IPv4 address with less than 3 dots
o it is an IPv4 address with a ``/XX'' suffix (where XX is the number
of bits in the network portion of the address and is less than 32)
o it is an IPv6 address with a ``/XX'' suffix (where XX is the number
of bits in the network portion of the address and is less than 128)
o it is the symbolic name of a network.
If destination is a valid IP address or host name, it is presumed to be a
route to a host.
For example, 192.168.1.1 is interpreted as -host 192.168.1.1 and
192.168.1 is interpreted as -net 192.168.1. Note, however, that
192.168.2.0 will be interpreted as -host 192.168.2.0 since it is a
complete IP address with 3 dots. In this case the number of bits in the
network portion of the address must be explicitly listed, for example
192.168.2.0/24, 192.168.2/24, or alternately 192.168.2.
If the destination is directly reachable via an interface requiring no
intermediary system to act as a gateway, the -iface modifier should be
specified; the gateway given is the address of this host on the common
network, indicating the interface to be used for transmission.
To allow addresses to be interpreted as belonging to a particular address
family (as well as for use in the family arguments to some commands), the
following modifiers may be used:
-inet Internet Protocol version 4 (IPv4) addresses (see ip(4))
-inet6 Internet Protocol version 6 (IPv6) addresses (see ip6(4))
-link Hardware (link-level) addresses
-mpls MPLS addresses
-sa Actual sockaddr data, in hexadecimal format
In the absence of modifiers, an address is assumed to be IPv4, unless
containing a `:' character, when it is treated as IPv6.
The optional modifier -link specifies that all subsequent addresses are
specified as link-level addresses, and the names must be numeric
specifications rather than symbolic names.
The optional -netmask qualifier is intended to manually add subnet routes
with netmasks different from that of the implied network interface (as
would otherwise be communicated using a routing protocol). One specifies
an additional ensuing address parameter (to be interpreted as a network
mask). The implicit network mask generated in the AF_INET case can be
overridden by making sure this option follows the destination parameter.
-prefixlen is also available for a similar purpose, for IPv6/v4.
A specific routing priority can be specified with the optional -priority
qualifier. If no priority is specified the kernel will set a priority
depending on the RTF_STATIC flag to either RTP_STATIC or RTP_DEFAULT.
Note that priority 1 is reserved for kernel use.
The optional -mpath modifier needs to be specified with the add command
to be able to enter multiple gateways for the same destination address
(multipath). When multiple routes exist for a destination, one route is
selected based on the source address of the packet. The sysctl(8)
variables net.inet.ip.multipath and net.inet6.ip6.multipath are used to
control multipath routing. If set to 1, multiple routes with the same
priority are used equally; if set to 0, the first route selected will be
used for subsequent packets to that destination regardless of source.
When inserting MPLS routes, particular modifiers must be used. The
-mplslabel modifier needs to be specified in an ingress LSR to associate
a particular label to an IPv4/IPv6 route. The MPLS traffic -in and -out
modifiers are intended to identify the ingress label and, optionally, the
outgoing one. Additionally, one of the following operations must be
used: -push, -pop and -swap. Route's nexthop can be specified with the
Routes have associated flags which influence operation of the protocols
when sending to destinations matched by the routes. These flags may be
set (or sometimes cleared) by indicating the following corresponding
-blackhole RTF_BLACKHOLE silently discard pkts (during updates)
-cloning RTF_CLONING generates a new route on use
-iface ~RTF_GATEWAY destination is directly reachable
-llinfo RTF_LLINFO validly translates proto addr to link addr
-mpath RTF_MPATH multiple gateways for a destination exist
-nostatic ~RTF_STATIC pretend route added by kernel or daemon
-proto1 RTF_PROTO1 set protocol specific routing flag #1
-proto2 RTF_PROTO2 set protocol specific routing flag #2
-reject RTF_REJECT emit an ICMP unreachable when matched
-static RTF_STATIC manually added route
The optional modifiers -expire and -mtu provide initial values to
quantities maintained in the routing entry by transport level protocols,
such as TCP (see tcp(4)). They have the following meanings:
-expire n Lifetime for route (e.g., if generated by a redirect).
-mtu n Maximum transmission unit (MTU) size for this path.
These may be individually locked by preceding each such modifier to be
locked by the -lock meta-modifier, or one can specify that all ensuing
metrics may be locked by the -lockrest meta-modifier.
In a change or add command where the destination and gateway are not
sufficient to specify the route, the -ifp or -ifa modifiers may be used
to determine the interface name or interface address.
The optional -label modifier specifies on route addition or modification
that the route should have the given label associated with it. Route
labels can be used to attach arbitrary information to a route.
All symbolic names specified for a destination or gateway are looked up
first as a network name using getnetbyname(3). If this lookup fails,
gethostbyname(3) is then used to interpret the name as a valid host name.
route uses a routing socket (see route(4)) and the message types RTM_ADD,
RTM_DELETE, RTM_GET, and RTM_CHANGE. As such, only the superuser may
modify the routing tables.
/etc/hosts host name database
/etc/mygate default gateway address
/etc/networks network name database
Add a static inet(4) route to the 192.168.5.0/24 network via the
# route add -inet 192.168.5.0/24 192.168.0.1
Amend the inet(4) route to the 192.168.5.0/24 network to use the
# route change -inet 192.168.5.0/24 192.168.0.2
Delete the inet(4) route to the 192.168.5.0/24 network:
# route delete -inet 192.168.5.0/24
%s: gateway %s flags %x The specified route is being added to or deleted
from the tables. If the gateway address used was not the primary address
of the gateway (the first one returned by gethostbyname(3)), the gateway
address is printed numerically as well as symbolically.
%s %s done When the flush command is specified, each routing table entry
deleted is indicated with a message of this form.
Network is unreachable An attempt to add a route failed because the
gateway listed was not on a directly connected network. The next-hop
gateway must be given.
not in table A delete operation was attempted for an entry which wasn't
present in the tables.
routing table overflow An add operation was attempted, but the system
was low on resources and was unable to allocate memory to create the new
netstat(1), gethostbyname(3), getnetbyname(3), netintro(4), route(4),
tcp(4), hosts(5), mygate(5), networks(5), bgpd(8), ospfd(8), ripd(8),
The route command appeared in 4.2BSD. IPv6 support was added by
The -recvpipe, -hopcount, -sendpipe, -ssthres, -rtt, and -rttvar
modifiers used to be used to initialize various quantities in routing
table entries. The routing system no longer uses these values and the
modifiers exist now only for compatibility with other operating systems.
Some uses of the -ifa or -ifp modifiers with the add command will
incorrectly fail with a ``Network is unreachable'' message if there is no
default route. See case RTM_ADD in route_output() from sys/net/rtsock.c
OpenBSD 5.9 September 11, 2015 OpenBSD 5.9
[Unix Hosting |
[Engineering & Automation |
Software Development |