The route
utility is used to manually manipulate the
network routing tables. It normally is not needed, as a system routing table
management daemon, such as
routed(8),
should tend to this task.
The route
utility supports a limited
number of general options, but a rich command language, enabling the user to
specify any arbitrary request that could be delivered via the programmatic
interface discussed in
route(4).
The following options are available:
-4
- Specify
inet
address family as family hint for
subcommands.
-6
- Specify
inet6
address family as family hint for
subcommands.
-d
- Run in debug-only mode, i.e., do not actually modify the routing
table.
-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 forget this,
especially when attempting to repair networking operations).
-t
- Run in test-only mode. /dev/null is used instead
of a socket.
-v
- (verbose) Print additional details.
-q
- Suppress all output from the
add
,
change
, delete
, and
flush
commands.
The route
utility provides the following
commands:
add
- Add a route.
flush
- Remove all routes.
delete
- Delete a specific route.
del
- Another name for the
delete
command.
change
- Change aspects of a route (such as its gateway).
get
- Lookup and display the route for a destination.
monitor
- Continuously report any changes to the routing information base, routing
lookup misses, or suspected network partitionings.
show
- Another name for the
get
command.
The monitor command has the syntax:
route
[-n
] monitor
[-fib
number]
The flush command has the syntax:
route
[-n
] flush
[family] [-fib
number]
If the flush
command is specified,
route
will ``flush'' the routing tables of all
gateway entries. When the address family may is specified by any of the
-osi
, -xns
,
-inet6
, or -inet
modifiers,
only routes having destinations with addresses in the delineated family will
be deleted. Additionally, -4
or
-6
can be used as aliases for
-inet
and -inet6
modifiers.
When a -fib
option is specified, the operation will
be applied to the specified FIB (routing table).
The add command has the following syntax:
route
[-n
] add
[-net
|
-host
] destination gateway
[netmask] [-fib
number]
and the other commands have the following syntax:
route
[-n
] command
[-net
|
-host
] destination
[gateway [netmask]]
[-fib
number]
where 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
force the destination to be interpreted as a network or a host,
respectively. Otherwise, if the destination has a
“local address part” of INADDR_ANY
(0.0.0.0
), or if the
destination is the symbolic name of a network, then
the route is assumed to be to a network; otherwise, it is presumed to be a
route to a host. Optionally, the destination could
also be specified in the
net/bits format.
For example, 128.32
is interpreted as
-host
128.0.0.32
;
128.32.130
is interpreted as
-host
128.32.0.130
;
-net
128.32
is interpreted
as 128.32.0.0;
-net
128.32.130
is interpreted as
128.32.130.0;
and
192.168.64/20
is interpreted as
-net
192.168.64
-netmask
255.255.240.0
.
A destination of
default is a synonym for the default route. For
IPv4
it is -net
-inet
0.0.0.0
, and for
IPv6
it is -net
-inet6
::
.
If the destination is directly reachable via an interface
requiring no intermediary system to act as a gateway, the
-interface
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. Alternately, if the interface is
point to point the name of the interface itself may be given, in which case
the route remains valid even if the local or remote addresses change.
The optional modifiers -xns
,
-osi
, and -link
specify that
all subsequent addresses are in the XNS or OSI address families, or are
specified as link-level addresses, and the names must be numeric
specifications rather than symbolic names.
The optional -netmask
modifier is intended
to achieve the effect of an OSI ESIS redirect with the netmask option, or to
manually add subnet routes with netmasks different from that of the implied
network interface (as would otherwise be communicated using the OSPF or ISIS
routing protocols). 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.
For AF_INET6
, the
-prefixlen
qualifier is available instead of the
-mask
qualifier because non-continuous masks are not
allowed in IPv6. For example, -prefixlen
32
specifies that a network mask of
ffff:ffff:0000:0000:0000:0000:0000:0000
will be
used. The default prefixlen is 64. However, it is assumed to be 0 if
default
is specified for
destination. Note that the qualifier works only for
AF_INET6
address family.
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:
-xresolve RTF_XRESOLVE - emit mesg on use (for external lookup)
-iface ~RTF_GATEWAY - destination is directly reachable
-static RTF_STATIC - manually added route
-nostatic ~RTF_STATIC - pretend route added by kernel or daemon
-reject RTF_REJECT - emit an ICMP unreachable when matched
-blackhole RTF_BLACKHOLE - silently discard pkts (during updates)
-proto1 RTF_PROTO1 - set protocol specific routing flag #1
-proto2 RTF_PROTO2 - set protocol specific routing flag #2
The optional modifiers -rtt
,
-rttvar
, -sendpipe
,
-recvpipe
, -mtu
,
-hopcount
, -expire
, and
-ssthresh
provide initial values to quantities
maintained in the routing entry by transport level protocols, such as TCP or
TP4. 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.
Note that -expire
accepts expiration time
of the route as the number of seconds since the Epoch (see
time(3)).
When the first character of the number is “+” or
“-”, it is interpreted as a value relative to the current
time.
The optional modifier -fib
number specifies that the command will be applied to a
non-default FIB. The number must be smaller than the
net.fibs
sysctl(8)
MIB. When this modifier is not specified, or a negative number is specified,
the default FIB shown in the net.my_fibnum
sysctl(8)
MIB will be used.
The number allows multiple FIBs by a
comma-separeted list and/or range specification. The
“-fib
2,4,6
”
means the FIB number 2, 4, and 6. The “-fib
1,3-5,6
” means the 1, 3, 4, 5, and 6.
In a change
or add
command where the destination and gateway are not sufficient to specify the
route (as in the ISO case where several interfaces may have the same
address), the -ifp
or -ifa
modifiers may be used to determine the interface or interface address.
All symbolic names specified for a
destination or gateway are
looked up first as a host name using
gethostbyname(3).
If this lookup fails,
getnetbyname(3)
is then used to interpret the name as that of a network.
The route
utility uses a routing socket
and the new message types RTM_ADD
,
RTM_DELETE
, RTM_GET
, and
RTM_CHANGE
. As such, only the super-user may modify
the routing tables.