ROUTE(8) BSD System Manager's Manual ROUTE(8)NAMEroute — manually manipulate the routing tables.
SYNOPSISroute [-nqv] command [[modifiers] args]
Route is a utility 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
-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),
-v (verbose) Print additional details.
-q Suppress all output.
The route: utility provides six commands:
add Add a route.
flush Remove all routes.
delete Delete a specific route.
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 partition‐
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 may is specified
by any of the -osi, -xns, or -inet modifiers, only routes having destina‐
tions with addresses in the delineated family will be deleted.
The other commands have the following syntax:
route [-n] command [-net | -host] destination gateway
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 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
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 22.214.171.124; 128.32.130 is
interpreted as -host 126.96.36.199; -net 128.32 is interpreted as
188.8.131.52; and -net 128.32.130 is interpreted as 184.108.40.206.
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, and -link specify that all subsequent
addresses are in the XNS OSI address families, or are specified as link-
level addresses, and the names must be numeric specifications rather than
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
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‐
-cloning RTF_CLONING - generates a new route on use
-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
-llinfo RTF_LLINFO - validly translates proto addr to link addr
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.
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
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
SEE ALSOnetintro(4), route(4), esis(4), routed(8), XNSrouted(8)HISTORY
The route command appeared in 4.2BSD.
The first paragraph may have slightly exaggerated routed's abilities.
4.4BSD June 1, 1994 4.4BSD