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route(8)
NAME
route - Manipulates the routing tables manually
SYNOPSIS
Adding a Route
route [-nqvC] add [-net|-host]
destination[/bitmask] gateway [modifiers [args]]
Changing a Route
route [-nqv] change [-net|-host]
destination gateway [modifiers [args]]
Monitoring a Route
route [-n] monitor
Deleting a Route
route [-nqvC] delete [-net|-host]
destination[/bitmask] gateway [modifiers [args]]
Deleting All Routes
route [-nqvC] flush [-inet]
FLAGS
-n Prints host and network names in numeric format, instead of symbolic
format, when reporting actions.
-q Suppresses all output.
-v Causes additional details to be printed.
-C Forces route to use the old ioctl calls instead of the current route
server request path.
PARAMETERS
-net Specifies explicitly that this route is a network route;
destination is interpreted as a network address.
-host Specifies explicitly that this route is a host route; destination
is interpreted as a host address.
destination
Specifies the destination host or network (with or without the
optional Classless Inter-Domain Routing (CIDR) mask (/bitmask)).
gateway Specifies the next hop and gateway to which packets should be
addressed.
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 gateway entries from the routing tables. You can
choose to flush only those routes whose destinations are of a
given address family by specifying an optional keyword describing
which address family.
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.
Unless the -net or -host parameters are specified on the command line,
route creates a host route or a network route by interpreting the Internet
address associated with destination parameter. If the destination has a
local address part of INADDR_ANY, or if the destination is the symbolic
name of a network, a network route is created; otherwise, a host route is
created.
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.
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.
Routes added with the route command are marked as RTF_STATIC to
differentiate them from routes added by the routing daemons (gated or
routed). The gated daemon does not remove the RTF_STATIC routes when it is
shut down.
The route command uses a routing socket and the new message types RTM_ADD,
RTM_DELETE, and RTM_CHANGE.
Modifiers
Modifiers provide initial values to metrics and other information
maintained in the routing entry. All modifiers and their arguments are
optional and must appear after the gateway field on the command line. The
modifiers for the add, change, and delete commands are as follows:
-all Specifies that the kernel add or delete the specified route on
all interfaces (for example, tu0 and tu1) that are in the same
subnet as the gateway. Use this modifier only with the add and
delete modifiers. Do not use -all with the -dev and -olddev
modifiers.
-blackhole
Specifies that this route is a blackhole route. Packets sent to
blackhole routes are dropped, and no notification is sent to the
packet originators. This is different from a normal route, which
allows packets to be forwarded out on it. You must specify
127.0.0.1 (localhost) as the gateway argument.
-cloning Generates a new route on use of this route.
-dev device
Specifies the interface device (for example, tu0 and fta0) to use
in the routing entry. Use this modifier when you want to
designate a particular interface for a route. If you do not
specify this modifier, the route is added on the first interface
that is found.
-genmask mask
Specifies that the netmask mask is used for all routes cloned
from this route.
-hopcount count
Sets this route's maximum hopcount to count.
-iface | -interface
Specifies that this route is via an interface instead of via a
gateway (the default). This means the destination is reachable
directly via an interface; no intermediate system is required to
act as a gateway. The gateway parameter is the address of this
host on the common network, indicating the interface to be used
for transmission.
-inet Sets this route's type as AF_INET. When used with the delete or
flush commands, only AF_INET routes are deleted.
-iso Sets this route's type as AF_ISO. When used with the delete or
flush commands, only AF_ISO routes are deleted.
-link Sets this route's type as AF_LINK. When used with the delete or
flush commands, only AF_LINK routes are deleted.
-lock Locks the metric set by next modifier specified on the command
line in the routing entry. The following metrics can be locked:
mtu, hopcount, recvpipe, sendpipe, ssthresh, rtt, and rttvar.
-lockrest Locks the metrics set by all modifiers that follow on the command
line in the routing entry. The following metrics can be locked:
mtu, hopcount, recvpipe, sendpipe, ssthresh, rtt, and rttvar.
-mtu size Sets this route's maximum transmission unit (MTU), in bytes, to
size.
-netmask mask
Specifies the subnet mask to use for the routing entry. Networks
that use a nonstandard subnet must include this modifier.
Specify this modifier after any optional modifiers. Do not
specify this modifier if you specify a CIDR bitmask (/bitmask).
Do not specify this modifier with the change command.
-olddev device
Specifies the old interface device (for example, tu0 and fta0) in
the routing entry that you want to change. Use this modifier
with the change command only to move a route from one interface
to another. See the "Examples" section.
-oldgateway name
Specifies the old gateway in the routing entry that you want to
change. Use this modifier with the change command only. See the
"Examples" section.
-osi Sets this route's type as AF_ISO. When used with the delete or
flush commands, only AF_ISO routes are deleted.
-recvpipe bandwidth
Sets this route's inbound delay bandwidth product (in bytes) to
bandwidth.
-reject Specifies that this route is a reject route. Packets sent to
reject routes are dropped and messages designating the route as
unreachable are sent to the packet originators. This is
different from a normal route, which allows packets to be
forwarded out on it. You must specify 127.0.0.1 (localhost) as
the gateway argument.
-rtt time Sets this route's round trip time (in microseconds) to time.
-rttvar variance
Sets this route's round trip time variance (in microseconds) to
variance.
-sendpipe bandwidth
Sets this route's outbound delay bandwidth product (in bytes) to
bandwidth.
-ssthresh threshold
Sets this route's outbound gateway buffer limit (in bytes) to
threshold.
RESTRICTIONS
You must be superuser in order to run the route command and to modify the
routing tables.
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
3. To delete an existing route via gateway 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.
5. To add a route to network 212.232.32/22 via gateway 128.32.0.130 and
lock the MTU size at 1500, enter:
route add -net 197.45.63/24 214.89.32.235 -lock -mtu 1500
6. To add a route to network 212.232.32/22 via gateway 128.32.0.130 and
lock the MTU size and hop count, enter:
route add -net 197.45.63/24 214.89.32.235 -lockrest -mtu 1500 \
-hopcount 2
7. To change existing network route 206.98.17 via gateway 206.98.17.45
from using interface device tu0 to tu1, enter:
route change -net 206.98.17 206.98.17.45 -olddev tu0 -dev tu1
This assumes that interface device tu1 is configured with an IP
address in the same subnet as tu0.
8. To change existing network route 206.98.17 from using gateway
206.98.17.45 to 206.98.17.162, enter:
route change -net 206.98.17 206.98.17.162 -oldgateway 206.98.17.45
9. To change existing network route 206.98.17 using interface device tu0
and gateway 206.98.17.45 to use device tu1 and gateway 206.98.17.162,
enter:
route change -net 206.98.17 206.98.17.162 -olddev tu0 -dev tu1 \
-oldgateway 206.98.17.45
10. To add a route to host 219.67.129.16 via gateway 219.67.122.41 using
interface device tu1, enter:
route add -host 219.67.129.16 219.67.122.41 -dev tu1
11. To delete a route to network 219.84.6 via gateway 219.84.6.79 using
interface device fta0, enter:
route delete -net 219.84.6 219.84.6.79 -olddev fta0
12. To add a route to host 202.54.164.79 via gateway 202.54.163.11 using
all interfaces connected to the 202.54.163/24 subnet, enter:
route add -host 202.54.164.79 202.54.163.11 -all
DIAGNOSTICS
Add [host | network] %s: gateway %s flags %x
The specified route is being added to the tables. 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.
Bitmask cannot be used with change command
The optional /bitmask parameter was specified with the change
command. Do not specify a bit mask with the change command.
Delete [ host | network ] %s: gateway %s flags %x
The specified route is being deleted from the tables. 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.
%s %s done
When you use the flush command, each routing table entry deleted
is indicated with a message of this form.
Entry exists
An add operation was attempted for an entry that already exists
in the routing tables.
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 cannot be used with bitmask.
The -netmask modifier was specified together with a CIDR bit
mask.
Netmask cannot be used with change command
The optional -netmask modifier was specified with the change
command. Do not specify a network mask with the change command.
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: netstat(1), gated(8), routed(8).
Networking: netintro(7).
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Index for
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