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route(8)
NAME
route - Manually manipulates the routing tables
SYNOPSIS
route [-nqvC] command [modifiers] [args]
FLAGS
-n Prevents attempts to print host and network names symbolically
when reporting actions.
-v Causes additional details to be printed.
-q Suppresses all output.
-C Forces route to use the old ioctl calls instead of the current
route server request path.
DESCRIPTION
The route command is a program used to manually manipulate the network
routing tables. It normally is not needed, as a system routing table
management daemon, such as gated or routed, should tend to this task.
The route command accepts five commands:
add Adds a route.
flush Removes all routes.
delete Deletes a specific route.
change Changes aspects of a route (such as its gateway).
monitor Reports any changes to the routing information base, routing
lookup misses, or suspected network partionings.
The monitor command has the syntax:
route [-n] monitor
The flush command has the syntax:
route [-n] flush [family]
where the address family may be specified by the -inet keyword.
The other commands have the following syntax:
route [-n] [-C] command [-net|-host] destination[/bitmask]
gateway modifier [-netmask mask]
where destination is the destination host or network (with or without the
optional Classless Inter-Domain Routing (CIDR) mask (/bitmask)), and
gateway is the next hop and gateway to which packets should be addressed.
Routes to a particular host are distinguished from those to a network by
interpreting the Internet address associated with destination. The
optional keywords -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, 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.
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, and -net 128.32.130 is interpreted as 128.32.130.0.
If the route is via an interface rather than via 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.
The optional modifiers -rtt, -rttvar, -sendpipe, -recvpipe, -mtu, -
hopcount, -expire, and -ssthresh provide initial values to metrics
maintained in the routing entry. 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.
The optional modifiers -reject and -blackhole specify route behavior
different from a normal route. A normal route allows packets to be
forwarded out on it. Packets sent to reject routes are dropped and
messages designating the route as unreachable are sent to the packet
originators. Packets sent to blackhole routes are also dropped, but no
notification is sent to the packet originators. In both cases, you must
specify 127.0.0.1 (localhost) as the gateway argument.
The -netmask mask option specifies the subnet mask to use for the routing
entry. Networks that use a nonstandard subnet must include this option.
Specify this option after any optional modifiers. Do not specify this
option if you specify a CIDR bitmask (/bitmask).
All symbolic names specified for a destination or gateway are looked up
first as a hostname using gethostbyname(3). If this lookup fails,
getnetbyname(3) is then used to interpret the name as that of a network.
The route command uses a routing socket and the new message types RTM_ADD,
RTM_DELETE, and RTM_CHANGE. As such, only the superuser may modify the
routing tables.
If the flush command is specified, route will flush the routing tables of
all gateway entries. One can choose to flush only those routes whose
destinations are of a given address family by specifying an optional
keyword describing which address family.
EXAMPLES
1. To add gateway 128.32.0.130 as a default gateway, enter:
route add default 128.32.0.130
2. To add a route to host milan via gateway 128.32.0.130, enter:
route add -host milan 128.32.0.130 -hopcount 2
where 2 is the distance in hops to the host.
3. To delete an existing route 128.32.0.130 to host milan, enter:
route delete -host milan 128.32.0.130
4. To add a route to network 212.232.32 via gateway 128.32.0.130, enter:
route add -net 212.232.32/22 128.32.0.130
The previous example aggregates routes for four Class C networks:
212.232.32, 212.232.33, 212.232.34, and 212.232.35.
DIAGNOSTICS
Add [host | network] %s: gateway %s flags %x
The specified route is being added to the tables. The values
printed are from the routing table entry supplied in the ioctl
call. If the gateway address used was not the primary address of
the gateway (the first one returned by gethostbyname), the
gateway address is printed numerically as well as symbolically.
Delete [ host | network ] %s: gateway %s flags %x
As above, but when deleting an entry.
%s %s done
When the -f flag is specified, each routing table entry deleted
is indicated with a message of this form.
Gateway must be 127.0.0.1 for reject and blackhole routes.
The gateway value is incorrect for creating reject and blackhole
routes.
Invalid bitmask
The bitmask specified is not in the range of 1 to 32, inclusive.
Netmask can not be used with bitmask.
The -netmask option was specified together with a CIDR bitmask.
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 that was not
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
entry.
FILES
/usr/sbin/route
Specifies the command path
RELATED INFORMATION
Commands: routed(8), gated(8)
Files: netintro(7)