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ROUTE(8)		  BSD System Manager's Manual		      ROUTE(8)

     route -- manually manipulate the routing tables

     route [-dnqtv] command [[modifiers] args]

     The route utility is used to manually manipulate the network routing ta-
     bles.  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

     The following options are available:

     -d	     Run in debug-only mode, i.e., do not actually modify the routing

     -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 ex-
	     pedient to	forget this, especially	when attempting	to repair net-
	     working operations).

     -v	     (verbose) Print additional	details.

     -q	     Suppress all output from the add, change, delete, and flush com-

     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 ta-
     bles of all gateway entries.  When	the address family may is specified by
     any of the	-osi, -xns, -atalk, -inet6, or -inet modifiers,	only routes
     having destinations with addresses	in the delineated family will be

     The other commands	have the following syntax:

	   route [-n] command [-net | -host] destination gateway [netmask]

     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 net-
     work; 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; 128.32.130	is in-
     terpreted as -host; -net 128.32 is interpreted as; -net 128.32.130 is interpreted	as; and
     192.168.64/20 is interpreted as -net 192.168.64 -netmask

     A destination of default is a synonym for -net, which is the de-
     fault route.

     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.  Alter-
     nately, if	the interface is point to point	the name of the	interface it-
     self may be given,	in which case the route	remains	valid even if the lo-
     cal or remote addresses change.

     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, 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	proto-
     cols).  One specifies an additional ensuing address parameter (to be in-
     terpreted 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 ex-
     ample, -prefixlen 32 specifies network mask of
     ffff:ffff:0000:0000:0000:0000:0000:0000 to	be used.  The default value of
     prefixlen is 64 to	get along with the aggregatable	address.  But 0	is as-
     sumed if default is specified.  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 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 en-
     suing 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 de-
     termine the interface or interface	address.

     The optional -proxy modifier specifies that the RTF_LLINFO	routing	table
     entry is the "published (proxy-only)" ARP entry, as reported by arp(8).

     The optional -genmask modifier specifies that a cloning mask is present.
     This specifies the	mask applied when determining if a child route should
     be	created.  It is	only applicable	to network routes with the RTF_CLONING
     flag set.

     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.

     The route utility exits 0 on success, and >0 if an	error occurs.

     add [host | network ] %s: gateway %s flags	%x  The	specified route	is be-
     ing 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

     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 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

     gateway uses the same route  A change operation resulted in a route whose
     gateway uses the same route as the	one being changed.  The	next-hop gate-
     way should	be reachable through a different route.

     netintro(4), route(4), arp(8), IPXrouted(8), routed(8)

     The route utility appeared	in 4.2BSD.

     The first paragraph may have slightly exaggerated routed(8)'s abilities.

     Currently,	routes with the	RTF_BLACKHOLE flag set need to have the	gate-
     way set to	an instance of the lo(4) driver, using the -iface option, for
     the flag to have any effect; unless IP fast forwarding is enabled,	in
     which case	the meaning of the flag	will always be honored.

BSD				October	2, 2005				   BSD


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