path: root/sbin/route/route.8

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.\"     @(#)route.8	8.3 (Berkeley) 3/19/94
.\" $FreeBSD$
.\"
.Dd October 2, 2005
.Dt ROUTE 8
.Os
.Sh NAME
.Nm route
.Nd manually manipulate the routing tables
.Sh SYNOPSIS
.Nm
.Op Fl dnqtv
.Ar command
.Oo
.Op Ar modifiers
.Ar args
.Oc
.Sh DESCRIPTION
The
.Nm
utility is used to manually manipulate the network
routing tables.
It normally is not needed, as a
system routing table management daemon, such as
.Xr routed 8 ,
should tend to this task.
.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 .
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl d
Run in debug-only mode, i.e., do not actually modify the routing table.
.It Fl 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 expedient
to forget this, especially when attempting to repair networking operations).
.It Fl t
Run in test-only mode.
.Pa /dev/null
is used instead of a socket.
.It Fl v
(verbose) Print additional details.
.It Fl q
Suppress all output from the
.Cm add , change , delete ,
and
.Cm flush
commands.
.El
.Pp
The
.Nm
utility provides the following commands:
.Pp
.Bl -tag -width Fl -compact
.It Cm add
Add a route.
.It Cm flush
Remove all routes.
.It Cm delete
Delete a specific route.
.It Cm del
Another name for the
.Cm delete
command.
.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 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 -ragged -offset indent -compact
.Nm
.Op Fl n
.Cm monitor
.Ed
.Pp
The flush command has the syntax:
.Pp
.Bd -ragged -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 may is specified by any of the
.Fl osi ,
.Fl xns ,
.Fl atalk ,
.Fl inet6 ,
or
.Fl inet
modifiers, only routes having destinations with addresses in the
delineated family will be deleted.
.Pp
The other commands have the following syntax:
.Pp
.Bd -ragged -offset indent -compact
.Nm
.Op Fl n
.Ar command
.Op Fl net No \&| Fl host
.Ar destination gateway
.Op Ar netmask
.Ed
.Pp
where
.Ar destination
is the destination host or network,
.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
.Dq local address part
of
INADDR_ANY
.Pq Li 0.0.0.0 ,
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
could 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;
.Fl net Li 128.32.130
is interpreted as
.Li 128.32.130.0;
and
.Li 192.168.64/20
is interpreted as
.Fl net Li 192.168.64 Fl netmask Li 255.255.240.0 .
.Pp
A
.Ar destination
of
.Ar default
is a synonym for
.Fl net Li 0.0.0.0 ,
which is the default route.
.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.
Alternately, if the interface is point to point the name of the interface
itself may be given, in which case the route remains valid even
if the local or remote addresses change.
.Pp
The optional modifiers
.Fl xns ,
.Fl osi ,
.Fl atalk ,
and
.Fl link
specify that all subsequent addresses are in the
.Tn XNS ,
.Tn OSI ,
or
.Tn AppleTalk
address families,
or are specified as link-level addresses,
and the names must be numeric specifications rather than
symbolic names.
.Pp
The optional
.Fl netmask
modifier is intended
to achieve the effect of an
.Tn OSI
.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 AF_INET case
can be overridden by making sure this option follows the destination parameter.
.Pp
For
.Dv AF_INET6 ,
the
.Fl prefixlen
qualifier
is available instead of the
.Fl mask
qualifier because non-continuous masks are not allowed in IPv6.
For example,
.Fl prefixlen Li 32
specifies network mask of
.Li 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 assumed if
.Cm default
is specified.
Note that the qualifier works only for
.Dv AF_INET6
address family.
.Pp
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 modifiers:
.Bd -literal
-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
.Ed
.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 (as in the
.Tn ISO
case where several interfaces may have the
same address), 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
The
.Nm
utility uses a routing socket and the new message types
.Dv RTM_ADD , RTM_DELETE , RTM_GET ,
and
.Dv RTM_CHANGE .
As such, only the super-user may modify
the routing tables.
.Sh EXIT STATUS
.Ex -std
.Sh DIAGNOSTICS
.Bl -diag
.It "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 "delete [ host \&| network ] %s: gateway %s flags %x"
As above, but when deleting an entry.
.It "%s %s done"
When the
.Cm flush
command is specified, each routing table entry deleted
is indicated with a message of this form.
.It "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 "not in table"
A delete operation was attempted for an entry which
was not present in the tables.
.It "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 "gateway uses the same route"
A
.Cm change
operation resulted in a route whose gateway uses the
same route as the one being changed.
The next-hop gateway should be reachable through a different route.
.El
.Sh SEE ALSO
.\".Xr esis 4 ,
.Xr netintro 4 ,
.Xr route 4 ,
.Xr arp 8 ,
.Xr IPXrouted 8 ,
.Xr routed 8
.\".Xr XNSrouted 8
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.2 .
.Sh BUGS
The first paragraph may have slightly exaggerated
.Xr routed 8 Ns 's
abilities.
.Pp
Currently, routes with the
.Dv RTF_BLACKHOLE
flag set need to have the gateway set to an instance of the
.Xr lo 4
driver, using the
.Fl 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.