route supports a limited number of general options, but a rich command language. Users can specify an arbitrary request that can be delivered by means of the programmatic interface discussed in route(7P).
route uses a routing socket and the new message types RTM_ADD, RTM_DELETE, RTM_GET, and RTM_CHANGE. Only superusers can modify routing tables.
Flush the routing tables of all gateway entries. If you use the -f option in conjunction with any of the route sub-commands, route flushes the gateways before performing the sub-command. Specify the table to flush by placing the -inet or -inet6 modifier immediately after the -f option. If unspecified, flushing IPv4 (-inet) routes is the default.
Prevent attempts to print host and network names symbolically when reporting actions. This option is useful when name servers are unavailable.
Print additional details in verbose mode.
Suppress all output.
The following sub—commands are supported:
Add a route.
Change aspects of a route (such as its gateway).
Delete a specific route.
Remove all gateway entries from the routing table.
Look up and display the route for a destination.
Continuously report any changes to the routing information base, routing lookup misses, or suspected network partitionings.
The add and delete sub-commands have the following syntax:
route [ -fnvq ] cmd destination gateway [metric/netmask]
where cmd is add or delete, destination is the destination host or network, and gateway is the next-hop intermediary through which packets should be routed. Modifiers described in OPERANDS can be placed anywhere on the command line.
The get and change sub-commands have the following syntax:
route [ -fnvq ] cmd destination [gateway [metric/netmask]]
where cmd is get or change, destination is the destination host or network, and gateway is the next-hop intermediary through which packets should be routed. Modifiers described in OPERANDS can be placed anywhere on the command line.
The monitor sub-command has the following syntax:
route monitor [ -inet | -inet6 ]
route executes its sub-commands on routes to destinations by way of gateways.
By default, destination and gateway addresses are interpreted as IPv4 addresses. All symbolic names are tried first as a host name, using getipnodebyname(3SOCKET). If this lookup fails in the AF_INET case, getnetbyname(3SOCKET) interprets the name as that of a network.
Including an optional modifier on the command line before the address changes how the route sub-command interprets it.
The following modifiers are supported:
Force the address to be interpreted as an IPv4 address, that is, under the AF_INET address family.
Force the address to be interpreted as an IPv6 address, that is, under the AF_INET6 address family.
For IPv4 addresses, routes to a particular host are by default distinguished from those to a network by interpreting the Internet address specified as the destination. If the destination has a local address part (that is, the portion not covered by the netmask) of 0, or if the destination is resolved as 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.
You can force this selection by using one of the following modifiers:
Force the destination to be interpreted as a host.
Force the destination to be interpreted as a network.
- host 188.8.131.52
Two modifiers avoid confusion between addresses and keywords (for example., host used as a symbolic host name). You can distinguish a destination by preceding it with the -dst modifier. You can distinguish a gateway address by using the -gateway modifier. If the destination is directly reachable by way of an interface requiring no intermediary IP router to act as a gateway, this can be indicated by using the -interface or -iface modifier.
In the following example, the route does not refer to an external gateway (router), but rather to one of the machine's interfaces. Packets with IP destination addresses matching the destination and mask on such a route are sent out on the interface identified by the gateway address. For interfaces using the ARP protocol, this type of route is used to specify that all matching destinations are local to the physical link. That is, a host could be configured to ARP for all addresses, without regard to the configured interface netmask, by adding a default route using this command. For example:
example# route add default hostname -interface
where gateway address hostname is the name or IP address associated with the network interface over which all matching packets should be sent. On a host with a single network interface, hostname is usually the same as the nodename returned by the uname -n command. See uname(1).
For backward compatibility with older systems, directly reachable routes can also be specified by placing a 0 after the gateway address:
example# route add default hostname 0
This value was once a route metric, but this metric is no longer used. If the value is specified as 0, then the destination is directly reachable (equivalent to specifying -interface). If it is non-zero but cannot be interpreted as a subnet mask, then a gateway is used (default).
With the AF_INET address family or an IPv4 address, a separate subnet mask can be specified. This can be specified in one of the following ways:
IP address following the gateway address . This is typically specified in decimal dot notation as for inet_addr(3SOCKET) rather than in symbollic form.
IP address following the -netmask qualifier.
Slash character and a decimal length appended to the destination address.
If a subnet mask is not specified, the mask used is the subnet mask of the output interface selected by the gateway address, if the classful network of the destination is the same as the classful network of the interface. Otherwise, the classful network mask for the destination address is used.
Each of the following examples creates an IPv4 route to the destination 192.0.2.32 subnet with a subnet mask of 255.255.255.224:
example# route add 192.0.2.32/27 somegateway example# route add 192.0.2.32 -netmask 255.255.255.224 somegateway example# route add 192.0.2.32 somegateway 255.255.255.224
For IPv6, only the slash format is accepted. The following example creates an IPv6 route to the destination 33fe:: with a netmask of 16 one-bits followed by 112 zero-bits.
example# route add -inet6 3ffe::/16 somegateway
In cases where the gateway does not uniquely identify the output interface (for example, when several interfaces have the same address), you can use the -ifp ifname modifier to specify the interface by name. For example, -ifp lo0 associates the route with the lo0 interface.
Routes have associated flags that influence operation of the protocols when sending to destinations matched by the routes. These flags can be set (and in some cases cleared, indicated by ~) by including the following modifiers on the command line:
Destination is directly reachable
Alias for interface modifier
Manually added route
Pretend route was added by kernel or routing daemon
Emit an ICMP unreachable when matched
Silently discard packets duing updates
Set protocol specific routing flag #1
Set protocol specific routing flag #2
Do not advertise this route
Creates the specified redundant route
Assigns the default source address
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. These can be individually locked either by preceding each modifier to be locked by the -lock meta-modifier, or by specifying that all ensuing metrics can be locked by the -lockrest meta-modifier.
Lifetime for the entry. This optional modifier is not currently supported.
Maximum hop count. This optional modifier is not currently supported.
Maximum MTU in bytes.
Receive pipe size in bytes.
Round trip time in microseconds.
Round trip time variance in microseconds.
Send pipe size in bytes.
Send pipe size threshold in bytes.
The modifiers host and net are taken to be equivalent to -host and -net. To specify a symbolic address that matches one of these names, use the dst or gateway keyword to distinguish it. For example: -dst host
The following two flags are also accepted for compatibility with older systems, but have no effect.
The -ifa hostname modifier is also accepted, but has no effect.
List of default routers
List of host names and net addresses
List of network names and addresses
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
uname(1), in.ripngd(1M), in.routed(1M), netstat(1M), routed(1M), ioctl(2), getipnodebyname(3SOCKET), getnetbyname(3SOCKET), inet_addr(3SOCKET), defaultrouter(4), hosts(4), networks(4), attributes(5), ARP(7P), ip(7P), route(7P), routing(7P)
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 getipnodebyname(3SOCKET)) the gateway address is printed numerically as well as symbolically.
As add, but when deleting or changing an entry.
When the -f flag is specified, or the flush sub-command is used, each routing table entry deleted is indicated with a message of this form.
An attempt to add a route failed because the gateway listed was not on a directly-connected network. Give the next-hop gateway instead.
A delete operation was attempted for an entry that is not in the table.
An add operation was attempted for a route that already exists in the kernel.
An operation was attempted, but the system was unable to allocate memory to create the new entry.
Specifying that destinations are local (with the -interface modifier) assumes that the routers implement proxy ARP, meaning that they respond to ARP queries for all reachable destinations. Normally, using either router discovery or RIP is more reliable and scalable than using proxy ARP. See in.routed(1M) for information related to RIP.
Combining the all destinations are local route with subnet or network routes can lead to unpredictable results. The search order as it relates to the all destinations are local route are undefined and can vary from release to release.