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.\"     @(#)route.8	8.4 (Berkeley) 6/1/94
.\"
.Dd August 29, 2020
.Dt ROUTE 8
.Os
.Sh NAME
.Nm route
.Nd manually manipulate the routing tables
.Sh SYNOPSIS
.Nm
.Op Fl dfLnqSsTtv
.Ar command
.Oo
.Op Ar modifiers
.Ar args
.Oc
.Sh DESCRIPTION
.Nm
is a utility used to manually manipulate the network
routing tables.
Except for setting up the default route, it is normally not needed,
as a system routing table management daemon such as
.Xr routed 8 ,
should tend to this task.
.Pp
.Nm
can be used to modify nearly any aspect of the routing policy,
except packet forwarding, which can be manipulated through the
.Xr sysctl 8
command.
.Pp
The
.Nm
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
.Xr route 4 .
.Bl -tag -width Ds
.It Fl d
Turn on debugging
.It Fl f
Remove all routes (as per
.Cm flush ) .
If used in conjunction with the
.Cm add ,
.Cm change ,
.Cm delete
or
.Cm get
commands,
.Nm
removes the routes before performing the command.
.It Fl L
Don't show link layer entries in routing table.
.It Fl 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).
.It Fl q
Suppress all output from commands that manipulate the routing table.
.It Fl 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.
.It Fl s
(short) Suppresses all output from a
.Cm 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.
.It Fl T
Show tags in the route display.
.It Fl t
Test only, don't perform any actions.
.It Fl v
(verbose) Print additional details.
.El
.Pp
The
.Nm
utility provides several commands:
.Pp
.Bl -tag -width Fl -compact
.It Cm add
Add a route.
.It Cm flush
Remove all routes.
.It Cm flushall
Remove all routes including the default gateway.
.It Cm delete
Delete a specific route.
.It Cm change
Change aspects of a route (such as its gateway).
.It Cm get
Lookup and display the route for a destination.
.It Cm show
Print out the route table similar to "netstat \-r" (see
.Xr netstat 1 ) .
.It Cm monitor
Continuously report any changes to the routing information base,
routing lookup misses, or suspected network partitionings.
.El
.Pp
The monitor command has the syntax
.Pp
.Bd -filled -offset indent -compact
.Nm
.Op Fl n
.Cm monitor
.Op Fl c Ar count
.Ed
.Pp
If
.Ar count
is specified,
.Nm
exits after receiving
.Ar count
routing messages.
.Pp
The flush command has the syntax
.Pp
.Bd -filled -offset indent -compact
.Nm
.Op Fl n
.Cm flush
.Op Ar family
.Ed
.Pp
If the
.Cm flush
command is specified,
.Nm
will ``flush'' the routing tables of all gateway entries.
When the address family is specified by any of the
.Fl atalk ,
.Fl inet ,
.Fl inet6 ,
or
.Fl mpls
modifiers, only routes having destinations with addresses in the
delineated family will be manipulated.
.Pp
The other commands have the following syntax:
.Pp
.Bd -filled -offset indent -compact
.Nm
.Op Fl n
.Ar command
.Op Fl net No \&| Fl host
.Ar destination gateway
.Ed
.Pp
where
.Ar destination
is the destination host or network, and
.Ar 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
.Ar destination
argument.
The optional modifiers
.Fl net
and
.Fl host
force the destination to be interpreted as a network or a host, respectively.
Otherwise, if the
.Ar destination
has a ``local address part'' of
.Dv INADDR_ANY ,
or if the
.Ar 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
.Ar destination
can also be specified in the
.Ar net Ns / Ns Ar bits
format.
.Pp
For example,
.Li 128.32
is interpreted as
.Fl host Li 128.0.0.32 ;
.Li 128.32.130
is interpreted as
.Fl host Li 128.32.0.130 ;
.Fl net Li 128.32
is interpreted as
.Li 128.32.0.0 ;
and
.Fl net Li 128.32.130
is interpreted as
.Li 128.32.130.0 .
.Pp
The keyword
.Cm default
can be used as the
.Ar destination
to set up a default route to a smart
.Ar gateway .
If no other routes match, this default route will be used as a last resort.
.Pp
If the destination is directly reachable
via an interface requiring
no intermediary system to act as a gateway, the
.Fl 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.
.Pp
The optional modifiers
.Fl atalk ,
and
.Fl link
specify that all subsequent addresses are in the
.Tn AppleTalk
address family,
or are specified as link-level addresses in the form described in
.Xr link_addr 3 ,
and the names must be numeric specifications rather than
symbolic names.
.Pp
The optional modifier
.Fl 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
.Xr mpls 4
stack; therefore
.Nm
assumes that the subsequent addresses are in the
.Tn MPLS
address family.
See
.Xr mpls 4
for examples of setting routes involving MPLS.
.Pp
The optional
.Fl netmask
qualifier is intended
to achieve the effect of an
.Tn 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
.Dv AF_INET
case
can be overridden by making sure this option follows the destination parameter.
.Fl prefixlen
is also available for similar purpose, in IPv4 and IPv6 case.
.Pp
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:
.Bl -column "ID" "xnoblackhole" "xRTF_BLACKHOLE" "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
.It Sy "ID" Ta Sy "Modifier" Ta Sy " Flag Bit" Ta Sy "Description"
.It Li 1 Ta -proto1 Ta " RTF_PROTO1" Ta set protocol specific flag #1
.It Li 2 Ta -proto2 Ta " RTF_PROTO2" Ta set protocol specific flag #2
.It Li B Ta -blackhole Ta " RTF_BLACKHOLE" Ta discard pkts (during updates)
.It Li " " Ta -noblackhole Ta ~RTF_BLACKHOLE Ta clear blackhole flag
.It Li b Ta "" Ta " RTF_BROADCAST" Ta route represents a broadcast address
.It Li C Ta -cloning Ta " RTF_CLONING" Ta  (deprecated) same as
.Fl connected
.It Li " " Ta -nocloning Ta ~RTF_CLONING Ta (deprecated) same as
.Fl noconnected
.It Li C Ta -connected Ta " RTF_CONNECTED" Ta  treat as a connected route
.It Li " " Ta -noconnected Ta ~RTF_CONNECTED Ta stop treating a connected route
.It Li D Ta "" Ta " RTF_DYNAMIC" Ta created dynamically (redirect)
.It Li G Ta "" Ta " RTF_GATEWAY" Ta forward to dest by intermediary
.It Li " " Ta -iface Ta ~RTF_GATEWAY Ta destination is directly reachable
.It Li H Ta "" Ta " RTF_HOST" Ta host entry (net otherwise)
.It Li L Ta "" Ta " RTF_LLDATA" Ta local link, generated by ARP or NDP
.It Li l Ta "" Ta " RTF_LOCAL" Ta route represents a local address
.It Li M Ta "" Ta " RTF_MODIFIED" Ta modified dynamically (redirect)
.It Li p Ta -proxy Ta " RTF_ANNOUNCE" Ta make entry a link level proxy
.It Li R Ta -reject Ta " RTF_REJECT" Ta send ICMP unreachable on match
.It Li " " Ta -noreject Ta ~RTF_REJECT Ta clear reject flag
.It Li S Ta -static Ta " RTF_STATIC" Ta manually added route
.It Li " " Ta -nostatic Ta ~RTF_STATIC Ta pretend route added automatically
.It Li U Ta "" Ta " RTF_UP" Ta route usable
.El
.Pp
The optional modifiers
.Fl rtt ,
.Fl rttvar ,
.Fl sendpipe ,
.Fl recvpipe ,
.Fl mtu ,
.Fl hopcount ,
.Fl expire ,
and
.Fl 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
.Fl lock
meta-modifier, or one can
specify that all ensuing metrics may be locked by the
.Fl lockrest
meta-modifier.
.Pp
In a
.Cm change
or
.Cm add
command where the destination and gateway are not sufficient to specify
the route the
.Fl ifp
or
.Fl ifa
modifiers may be used to determine the interface or interface address.
.Pp
All symbolic names specified for a
.Ar destination
or
.Ar gateway
are looked up first as a host name using
.Xr gethostbyname 3 .
If this lookup fails,
.Xr getnetbyname 3
is then used to interpret the name as that of a network.
.Pp
.Nm
uses a routing socket and the new message types
.Dv RTM_ADD ,
.Dv RTM_DELETE ,
.Dv RTM_GET ,
and
.Dv RTM_CHANGE .
As such, only the super-user may modify
the routing tables.
.Sh EXIT STATUS
.Ex -std route
This includes the use of the
.Cm get
command to look up a route that is incomplete.
.Sh EXAMPLES
This sets the default route to 192.168.0.1:
.Dl route add default 192.168.0.1
This shows all routes, without DNS resolution (this is useful if the
DNS is not available):
.Dl route -n show
To install a static route through 10.200.0.1 to reach the network
192.168.1.0/28, use this:
.Dl route add -net 192.168.1.0 -netmask 255.255.255.240 10.200.0.1
.Sh DIAGNOSTICS
.Bl -tag -width Ds
.It Sy "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
.Xr ioctl 2
call.
If the gateway address used was not the primary address of the gateway
(the first one returned by
.Xr gethostbyname 3 ) ,
the gateway address is printed numerically as well as symbolically.
.It Sy "delete [ host \&| network ] %s: gateway %s flags %x"
As above, but when deleting an entry.
.It Sy "%s %s done"
When the
.Cm flush
command is specified, each routing table entry deleted
is indicated with a message of this form.
.It Sy "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.
.It Sy "not in table"
A delete operation was attempted for an entry which
wasn't present in the tables.
.It Sy "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 entry.
.It Sy "Permission denied"
The attempted operation is privileged.
Only root may modify the routing tables.
These privileges are enforced by the kernel.
.El
.Sh SEE ALSO
.Xr mpls 4 ,
.Xr netintro 4 ,
.Xr route 4 ,
.Xr routed 8 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .
IPv6 support was added by WIDE/KAME project.
.Pp
Since
.Nx 8.0 ,
.Fl cloned ,
.Fl nocloned ,
.Fl llinfo
and
.Fl xresolve
were obsolete and
.Fl cloning
and
.Fl nocloning
were deprecated.
.Fl connected
and
.Fl noconnected
appeared in
.Nx 8.0 .
.Sh BUGS
The first paragraph may have slightly exaggerated
.Xr routed 8 Ns 's
abilities.
.Pp
Some uses of the
.Fl ifa
or
.Fl ifp
modifiers with the add command will incorrectly fail with a
.Dq Network is unreachable
message if there is no default route.
See case
.Dv RTM_ADD
in
.Pa sys/net/rtsock.c:route_output
for details.