|ROUTE(8)||System Manager's Manual||ROUTE(8)|
route — manually
manipulate the routing tables
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
bgpd(8), should tend to this
route can be used to modify nearly any
aspect of the routing policy, except packet forwarding, which can be
manipulated through 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:
route utility provides the following
-gatewayis specified, only routes whose gateway are in the same address family as the destination are shown.
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.
-gateway is specified, only routes
whose gateway are in the same address family as the destination are
-label is specified, only routes
with the specified label are shown.
-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 the syntax:
add[modifiers] destination gateway
change[modifiers] destination gateway
ete] [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
cause the destination to be interpreted as a network or a host,
respectively. Otherwise, type is chosen based on the following rules:
The route is assumed to be to a network if any of the following apply to destination:
If destination is a valid IP address or host name, it is presumed to be a route to a host.
192.168.1.1 is interpreted as
192.168.1 is interpreted as
192.168.2.0 will be interpreted as
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
192.168.2/24, or alternately
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:
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.
-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
AF_INET case can be overridden by making sure
this option follows the destination parameter.
-prefixlen is also available for a similar purpose,
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
-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
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
modifiers are intended to identify the ingress label and, optionally, the
outgoing one. Additionally, one of the following operations must be used:
-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 modifiers:
||silently discard pkts (during updates)|
||generates a new route on use|
||destination is directly reachable|
||validly translates proto addr to link addr|
||multiple gateways for a destination exist|
||pretend route added by kernel or daemon|
||set protocol specific routing flag #1|
||set protocol specific routing flag #2|
||emit an ICMP unreachable when matched|
||manually added route|
The optional modifiers
-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
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
command where the destination and gateway are not sufficient to specify the
modifiers may be used to determine the interface name or interface
specifies on route addition or modification that the route should have the
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
such, only the superuser may modify the routing tables.
Add a static inet(4) route to the 192.168.5.0/24 network via the 192.168.0.1 gateway:
# 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 192.168.0.2 gateway:
# 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
flushcommand is specified, each routing table entry deleted is indicated with a message of this form.
deleteoperation was attempted for an entry which wasn't present in the tables.
addoperation was attempted, but the system was low on resources and was unable to allocate memory to create the new entry.
route command appeared in
4.2BSD. IPv6 support was added by WIDE/KAME
-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
-ifp modifiers with the
command will incorrectly fail with a “Network is unreachable”
message if there is no default route. See case
from sys/net/rtsock.c for details.
|September 6, 2017||OpenBSD-6.2|