MirBSD manpage: route(8)

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


     route - manually manipulate the routing tables


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


     route is a utility used to manually view and manipulate the network rout-
     ing tables. Except for setting up the default route, it normally is not
     needed to manipulate routes, as a system routing table management daemon,
     such as routed(8), ospfd(8), or bgpd(8), should tend to this task.

     route can be used to modify nearly any aspect of the routing policy, ex-
     cept packet forwarding, which can be manipulated through the sysctl(8)

     The route utility supports a limited number of general options, but a
     rich command language enables the user to specify any arbitrary request
     that could be delivered via the programmatic interface discussed in

     The options are as follows:

     -d      Run in debug-only mode, i.e., don't 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 forgo this, especially when attempting to repair net-
             working operations.)

     -q      Suppress all output.

     -t      Write routing messages to a fake device (/dev/null) instead of a
             real routing socket to test route manipulation.

     -v      (verbose) Print additional details.

     The route utility provides several commands:

     add         Add a route.
     change      Change aspects of a route (such as its gateway).
     delete      Delete a specific route.
     flush       Remove all routes.
     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-
     show        Print out the route table similar to "netstat -r" (see

     The get command has the syntax:

           route [-nv] get [modifiers] address

     The flush command has the syntax:

           route [-dnqtv] 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 one
     of the family modifiers (listed below), only routes having destinations
     with addresses in the delineated family will be deleted.

     The monitor command has the syntax:

           route [-dn] monitor

     The show command has the syntax:

           route [-n] show [family]

     The other commands have the syntax:

           route [-dnqtv] command [modifiers] destination gateway [netmask]

     destination is the destination host or network, gateway is the next-hop
     intermediary via which packets should be routed, and netmask behaves the
     same as the argument to the -netmask modifier and is described below.
     Routes to a particular host may be distinguished from those to a network
     by interpreting the Internet address specified as the destination argu-
     ment. The optional modifiers -net and -host cause the destination to be
     interpreted as a network or a host, respectively. Otherwise, type is
     chosen based on the following rules:

     The route is assumed to be to a network if any of the following apply to

     •   it is the word "default", equivalent to 0/0
     •   it is an IPv4 address with less than 3 dots
     •   it is an IPv4 address with a "/XX" suffix (where XX is the number of
         bits in the network portion of the address and is less than 32)
     •   it is the symbolic name of a network.

     If destination is a valid IP address or host name, it is presumed to be a
     route to a host.

     If none of the above apply, route prints an error message and exits.

     For example, is interpreted as -host and
     192.168.1 is interpreted as -net 192.168.1. Note, however, that will be interpreted as -host since it is a com-
     plete IP address with 3 dots. In this case the number of bits in the net-
     work portion of the address must be explicitly listed, for example, 192.168.2/24, or alternately 192.168.2.

     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.

     To allow addresses to be interpreted as belonging to a particular address
     family (as well as for use in the family arguments to some commands), the
     following modifiers may be used:

     -inet   Internet Protocol version 4 (IPv4) addresses (see ip(4))
     -inet6  Internet Protocol version 6 (IPv6) addresses (see ip6(4))
     -ipx    Novell's Internet Packet Exchange (IPX) addresses
     -link   Hardware (link-level) addresses
     -sa     Actual sockaddr data, in hexadecimal format

     The optional modifier -link specifies that all subsequent addresses are
     specified as link-level addresses, and the names must be numeric specifi-
     cations rather than symbolic names.

     The optional -netmask qualifier is intended to manually add subnet routes
     with netmasks different from that of the implied network interface (as
     would otherwise be communicated using a routing protocol). 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 a similar purpose, for IPv6/v4.

     The optional -mpath modifier needs to be specified with the add command
     to be able to enter multiple gateways for the same destination address

     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

     -blackhole   RTF_BLACKHOLE    silently discard pkts (during updates)
     -cloning     RTF_CLONING      generates a new route on use
     -iface       ~RTF_GATEWAY     destination is directly reachable
     -llinfo      RTF_LLINFO       validly translates proto addr to link addr
     -mpath       RTF_MPATH        multiple gateways for a destination exist
     -nostatic    ~RTF_STATIC      pretend route added by kernel or daemon
     -proto1      RTF_PROTO1       set protocol specific routing flag #1
     -proto2      RTF_PROTO2       set protocol specific routing flag #2
     -reject      RTF_REJECT       emit an ICMP unreachable when matched
     -static      RTF_STATIC       manually added route
     -xresolve    RTF_XRESOLVE     emit mesg on use (for external lookup)

     The optional modifiers -mtu and -expire provide initial values to quanti-
     ties maintained in the routing entry by transport level protocols, such
     as TCP (see tcp(4)). They have the following meanings:

     -expire n    Lifetime for route (e.g., if generated by a redirect).
     -mtu n       Maximum transmission unit (MTU) size for this path.

     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, the -ifp or -ifa modifiers may be used to
     determine the interface or interface address.

     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.

     The optional -label modifier specifies on route addition or modification
     that the route should have the given label associated with it. Route la-
     bels can be used to attach arbitrary information to a route.

     All symbolic names specified for a destination or gateway are looked up
     first as a network name using getnetbyname(3). If this lookup fails,
     gethostbyname(3) is then used to interpret the name as a valid host name.

     route uses a routing socket (see route(4)) and the message types RTM_ADD,
     RTM_DELETE, RTM_GET, and RTM_CHANGE. As such, only the superuser may
     modify the routing tables.


     /etc/hosts     host name database
     /etc/mygate    default gateway address
     /etc/networks  network name database


     %s: gateway %s flags %x  The specified route is being added to or deleted
     from the tables. The values printed are from the routing table entry sup-
     plied in the ioctl(2) call. If the gateway address used was not the pri-
     mary address of the gateway (the first one returned by gethostbyname(3)),
     the gateway address is printed numerically as well as symbolically.

     %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


     netstat(1), gethostbyname(3), getnetbyname(3), netintro(4), route(4),
     tcp(4), hosts(5), mygate(5), networks(5), bgpd(8), ospfd(8), routed(8),


     The route command appeared in 4.2BSD. IPv6 support was added by WIDE/KAME

     The -recvpipe, -hopcount, -sendpipe, -ssthres, -rtt, and -rttvar modif-
     iers used to be used to initialize various quantities in routing table
     entries. The routing system no longer uses these values and the modifiers
     exist now only for compatibility with other operating systems.


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

     Some uses of the -ifa or -ifp modifiers with the add command will in-
     correctly fail with a "Network is unreachable" message if there is no de-
     fault route. See case RTM_ADD in route_output() from sys/net/rtsock.c for

MirBSD #10-current              March 19, 1994                               3

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