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28 .\" @(#)route.8 8.3 (Berkeley) 3/19/94
36 .Nd manually manipulate the routing tables
48 utility is used to manually manipulate the network
50 It normally is not needed, as a
51 system routing table management daemon, such as
53 should tend to this task.
57 utility supports a limited number of general options,
58 but a rich command language, enabling the user to specify
59 any arbitrary request that could be delivered via the
60 programmatic interface discussed in
63 The following options are available:
64 .Bl -tag -width indent
66 Run in debug-only mode, i.e., do not actually modify the routing table.
68 Bypass attempts to print host and network names symbolically
69 when reporting actions.
70 (The process of translating between symbolic
71 names and numerical equivalents can be quite time consuming, and
72 may require correct operation of the network; thus it may be expedient
73 to forget this, especially when attempting to repair networking operations).
75 Run in test-only mode.
77 is used instead of a socket.
79 (verbose) Print additional details.
81 Suppress all output from the
82 .Cm add , change , delete ,
90 utility provides the following commands:
92 .Bl -tag -width Fl -compact
98 Delete a specific route.
104 Change aspects of a route (such as its gateway).
106 Lookup and display the route for a destination.
108 Continuously report any changes to the routing information base,
109 routing lookup misses, or suspected network partitionings.
116 The monitor command has the syntax:
118 .Bd -ragged -offset indent -compact
121 .Cm monitor Op Fl fib Ar number
124 The flush command has the syntax:
126 .Bd -ragged -offset indent -compact
128 .Oo Fl n Cm flush Oc Oo Ar family Oc Op Fl fib Ar number
133 command is specified,
135 will ``flush'' the routing tables of all gateway entries.
136 When the address family may is specified by any of the
143 modifiers, only routes having destinations with addresses in the
144 delineated family will be deleted.
147 option is specified, the operation will be applied to
151 The other commands have the following syntax:
153 .Bd -ragged -offset indent -compact
157 .Op Fl net No \&| Fl host
158 .Ar destination gateway
165 is the destination host or network,
167 is the next-hop intermediary via which packets should be routed.
168 Routes to a particular host may be distinguished from those to
169 a network by interpreting the Internet address specified as the
172 The optional modifiers
176 force the destination to be interpreted as a network or a host, respectively.
180 .Dq local address part
186 is the symbolic name of a network, then the route is
187 assumed to be to a network; otherwise, it is presumed to be a
191 could also be specified in the
192 .Ar net Ns / Ns Ar bits
198 .Fl host Li 128.0.0.32 ;
201 .Fl host Li 128.32.0.130 ;
205 .Fl net Li 128.32.130
211 .Fl net Li 192.168.64 Fl netmask Li 255.255.240.0 .
217 is a synonym for the default route.
221 .Fl net Fl inet Li 0.0.0.0 ,
225 .Fl net Fl inet6 Li :: .
227 If the destination is directly reachable
228 via an interface requiring
229 no intermediary system to act as a gateway, the
231 modifier should be specified;
232 the gateway given is the address of this host on the common network,
233 indicating the interface to be used for transmission.
234 Alternately, if the interface is point to point the name of the interface
235 itself may be given, in which case the route remains valid even
236 if the local or remote addresses change.
238 The optional modifiers
244 specify that all subsequent addresses are in the
250 or are specified as link-level addresses,
251 and the names must be numeric specifications rather than
257 to achieve the effect of an
260 redirect with the netmask option,
261 or to manually add subnet routes with
262 netmasks different from that of the implied network interface
263 (as would otherwise be communicated using the OSPF or ISIS routing protocols).
264 One specifies an additional ensuing address parameter
265 (to be interpreted as a network mask).
266 The implicit network mask generated in the AF_INET case
267 can be overridden by making sure this option follows the destination parameter.
274 is available instead of the
276 qualifier because non-continuous masks are not allowed in IPv6.
279 specifies network mask of
280 .Li ffff:ffff:0000:0000:0000:0000:0000:0000
282 The default value of prefixlen is 64 to get along with
283 the aggregatable address.
287 Note that the qualifier works only for
291 Routes have associated flags which influence operation of the protocols
292 when sending to destinations matched by the routes.
293 These flags may be set (or sometimes cleared)
294 by indicating the following corresponding modifiers:
296 -xresolve RTF_XRESOLVE - emit mesg on use (for external lookup)
297 -iface ~RTF_GATEWAY - destination is directly reachable
298 -static RTF_STATIC - manually added route
299 -nostatic ~RTF_STATIC - pretend route added by kernel or daemon
300 -reject RTF_REJECT - emit an ICMP unreachable when matched
301 -blackhole RTF_BLACKHOLE - silently discard pkts (during updates)
302 -proto1 RTF_PROTO1 - set protocol specific routing flag #1
303 -proto2 RTF_PROTO2 - set protocol specific routing flag #2
306 The optional modifiers
316 provide initial values to quantities maintained in the routing entry
317 by transport level protocols, such as TCP or TP4.
318 These may be individually locked by preceding each such modifier to
322 meta-modifier, or one can
323 specify that all ensuing metrics may be locked by the
327 The optional modifier
329 specifies that the command will be applied to a non-default FIB.
332 must be smaller than the
336 When this modifier is not specified,
337 or a negative number is specified,
338 the default FIB shown in the
345 allows multiple FIBs by a comma-separeted list and/or range
349 means the FIB number 2, 4, and 6.
351 .Qq Fl fib Li 1,3-5,6
352 means the 1, 3, 4, 5, and 6.
358 command where the destination and gateway are not sufficient to specify
361 case where several interfaces may have the
366 modifiers may be used to determine the interface or interface address.
368 All symbolic names specified for a
372 are looked up first as a host name using
373 .Xr gethostbyname 3 .
374 If this lookup fails,
376 is then used to interpret the name as that of a network.
380 utility uses a routing socket and the new message types
381 .Dv RTM_ADD , RTM_DELETE , RTM_GET ,
384 As such, only the super-user may modify
389 Add a default route to the network routing table.
390 This will send all packets for destinations not available in the routing table
391 to the default gateway at 192.168.1.1:
393 .Dl route add -net 0.0.0.0/0 192.168.1.1
395 A shorter version of adding a default route can also be written as:
397 .Dl route add default 192.168.1.1
399 Add a static route to the 172.16.10.0/24 network via the 172.16.1.1 gateway:
401 .Dl route add -net 172.16.10.0/24 172.16.1.1
403 Change the gateway of an already established static route in the routing table:
405 .Dl route change -net 172.16.10.0/24 172.16.1.2
407 Display the route for a destination network:
409 .Dl route show 172.16.10.0
411 Delete a static route from the routing table:
413 .Dl route delete -net 172.16.10.0/24 172.16.1.2
415 Remove all routes from the routing table:
420 .It "add [host \&| network ] %s: gateway %s flags %x"
421 The specified route is being added to the tables.
423 values printed are from the routing table entry supplied
427 If the gateway address used was not the primary address of the gateway
428 (the first one returned by
429 .Xr gethostbyname 3 ) ,
430 the gateway address is printed numerically as well as symbolically.
431 .It "delete [ host \&| network ] %s: gateway %s flags %x"
432 As above, but when deleting an entry.
436 command is specified, each routing table entry deleted
437 is indicated with a message of this form.
438 .It "Network is unreachable"
439 An attempt to add a route failed because the gateway listed was not
440 on a directly-connected network.
441 The next-hop gateway must be given.
443 A delete operation was attempted for an entry which
444 was not present in the tables.
445 .It "routing table overflow"
446 An add operation was attempted, but the system was
447 low on resources and was unable to allocate memory
448 to create the new entry.
449 .It "gateway uses the same route"
452 operation resulted in a route whose gateway uses the
453 same route as the one being changed.
454 The next-hop gateway should be reachable through a different route.
470 The first paragraph may have slightly exaggerated
474 Currently, routes with the
476 flag set need to have the gateway set to an instance of the
480 option, for the flag to have any effect; unless IP fast forwarding
481 is enabled, in which case the meaning of the flag will always