ROUTE(8) BSD System Manager's Manual ROUTE(8)NAMEroute — manually manipulate the routing tables
SYNOPSISroute [-fnqSsv] command [[modifiers] args]
DESCRIPTIONroute is a utility used to manually manipulate the network routing
tables. Except for setting up the default route, it is normally not
needed, as a system routing table management daemon such as routed(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)
command.
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).
-f Remove all routes (as per flush). If used in conjunction with
the add, change, delete or get commands, route removes the routes
before performing the command.
-n Bypasses attempts to print host and network names symbolically
when reporting actions. (The process of translating between sym‐
bolic names and numerical equivalents can be quite time consum‐
ing, and may require correct operation of the network; thus it
may be expedient to forgo this, especially when attempting to
repair networking operations).
-q Suppress all output from commands that manipulate the routing ta‐
ble.
-S Print a space when a flag is missing so that flags are vertically
aligned instead of printing the flags that are set as a contigu‐
ous string.
-s (short) Suppresses all output from a get command except for the
actual gateway that will be used. How the gateway is printed
depends on the type of route being looked up.
-v (verbose) Print additional details.
The route utility provides several commands:
add Add a route.
flush Remove all routes.
flushall Remove all routes including the default gateway.
delete Delete a specific route.
change Change aspects of a route (such as its gateway).
get Lookup and display the route for a destination.
show Print out the route table similar to "netstat -r" (see
netstat(1)).
monitor Continuously report any changes to the routing information
base, routing lookup misses, or suspected network partition‐
ings.
The monitor command has the syntax
route [-n] monitor
The flush command has the syntax
route [-n] flush [family]
If the flush command is specified, route will ``flush'' the routing
tables of all gateway entries. When the address family is specified by
any of the -osi, -xns, -atalk, -inet, -inet6, or -mpls modifiers, only
routes having destinations with addresses in the delineated family will
be manipulated.
The other commands have the following syntax:
route [-n] command [-net | -host] destination gateway
where destination is the destination host or network, and 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 inter‐
preting 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, or if the destination is the sym‐
bolic 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 can 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; and -net 128.32.130 is interpreted as 128.32.130.0.
The keyword default can be used as the destination to set up a default
route to a smart gateway. If no other routes match, this default route
will be used as a last resort.
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.
The optional modifiers -xns, -osi, -atalk, and -link specify that all
subsequent addresses are in the XNS, OSI, or AppleTalk address families,
or are specified as link-level addresses in the form described in
link_addr(3), and the names must be numeric specifications rather than
symbolic names.
The optional modifiers -mpls and -tag specify that all subsequent
addresses are in the MPLS address family. See mpls(4) for examples about
setting routes involving MPLS.
The optional -netmask qualifier 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 proto‐
cols). 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 similar purpose,
in IPv4 and IPv6 case.
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 mod‐
ifiers:
-cloning RTF_CLONING - generates a new route on use
-nocloning ~RTF_CLONING - stop generating new routes on use
-cloned RTF_CLONED - cloned route generated by RTF_CLONING
-nocloned ~RTF_CLONED - prevent removal with RTF_CLONING parent
-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
-noreject ~RTF_REJECT - clear reject flag
-blackhole RTF_BLACKHOLE - silently discard pkts (during updates)
-noblackhole ~RTF_BLACKHOLE - clear blackhole flag
-proto1 RTF_PROTO1 - set protocol specific routing flag #1
-proto2 RTF_PROTO2 - set protocol specific routing flag #2
-llinfo RTF_LLINFO - validly translates proto addr to link addr
-proxy RTF_ANNOUNCE - make entry a link level proxy
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.
In a change or add command where the destination and gateway are not suf‐
ficient 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.
route 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.
EXIT STATUS
The route utility exits 0 on success, and >0 if an error occurs. This
includes the use of the get command to look up a route that is incom‐
plete.
EXAMPLES
This sets the default route to 192.168.0.1:
route add default 192.168.0.1
This shows all routes, without DNS resolution (this is useful if the DNS
is not available):
route-n show
To install a static route through 10.200.0.1 to reach the network
192.168.1.0/28, use this:
route add -net 192.168.1.0 -netmask 255.255.255.240 10.200.0.1
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(2)
call. 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.
delete [ host | network ] %s: gateway %s flags %x
As above, but when deleting an entry.
%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
entry.
Permission denied
The attempted operation is privileged. Only root may modify the
routing tables. These privileges are enforced by the kernel.
SEE ALSOesis(4), mpls(4), netintro(4), route(4), routed(8), sysctl(8)HISTORY
The route command appeared in 4.2BSD. IPv6 support was added by
WIDE/KAME project.
BUGS
The first paragraph may have slightly exaggerated routed(8)'s abilities.
Some uses of the -ifa or -ifp modifiers with the add command will incor‐
rectly fail with a “Network is unreachable” message if there is no
default route. See case RTM_ADD in sys/net/rtsock.c:route_output for
details.
BSD August 6, 2006 BSD
