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DESCRIPTION

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).

-d

Turn on debugging

-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.

-L

Don't show link layer entries in routing table.

-n

Bypasses 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 expedient to forgo this, especially when attempting to repair networking operations).

-q

Suppress all output from commands that manipulate the routing table.

-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 contiguous 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.

-T

Show tags in the route display.

-t

Test only, don't perform any actions.

-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 partitionings.

The monitor command has the syntax

If count is specified, route exits after receiving count routing messages.

The flush command has the syntax

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 -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:

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 interpreting 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. 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 -atalk, and -link specify that all subsequent addresses are in the AppleTalk address family, 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 modifier -tag specifies an address associated with the route. How the address is used is specific to the address family of the destination and the interface used to forward the packet. Currently route tags are consumed only by the mpls(4) stack; therefore route assumes that the subsequent addresses are in the MPLS address family. See mpls(4) for examples of setting routes involving MPLS.

The optional -netmask qualifier is intended to achieve the effect of an 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 protocols). 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 are displayed using the following ID characters in the routing display and may be set (or sometimes cleared) by indicating the following corresponding modifiers:

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 sufficient to specify the route 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.