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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.
112 The monitor command has the syntax:
114 .Bd -ragged -offset indent -compact
120 The flush command has the syntax:
122 .Bd -ragged -offset indent -compact
131 command is specified,
133 will ``flush'' the routing tables of all gateway entries.
134 When the address family may is specified by any of the
141 modifiers, only routes having destinations with addresses in the
142 delineated family will be deleted.
144 The other commands have the following syntax:
146 .Bd -ragged -offset indent -compact
150 .Op Fl net No \&| Fl host
151 .Ar destination gateway
157 is the destination host or network,
159 is the next-hop intermediary via which packets should be routed.
160 Routes to a particular host may be distinguished from those to
161 a network by interpreting the Internet address specified as the
164 The optional modifiers
168 force the destination to be interpreted as a network or a host, respectively.
172 .Dq local address part
178 is the symbolic name of a network, then the route is
179 assumed to be to a network; otherwise, it is presumed to be a
183 could also be specified in the
184 .Ar net Ns / Ns Ar bits
190 .Fl host Li 128.0.0.32 ;
193 .Fl host Li 128.32.0.130 ;
197 .Fl net Li 128.32.130
203 .Fl net Li 192.168.64 Fl netmask Li 255.255.240.0 .
211 which is the default route.
213 If the destination is directly reachable
214 via an interface requiring
215 no intermediary system to act as a gateway, the
217 modifier should be specified;
218 the gateway given is the address of this host on the common network,
219 indicating the interface to be used for transmission.
220 Alternately, if the interface is point to point the name of the interface
221 itself may be given, in which case the route remains valid even
222 if the local or remote addresses change.
224 The optional modifiers
230 specify that all subsequent addresses are in the
236 or are specified as link-level addresses,
237 and the names must be numeric specifications rather than
243 to achieve the effect of an
246 redirect with the netmask option,
247 or to manually add subnet routes with
248 netmasks different from that of the implied network interface
249 (as would otherwise be communicated using the OSPF or ISIS routing protocols).
250 One specifies an additional ensuing address parameter
251 (to be interpreted as a network mask).
252 The implicit network mask generated in the AF_INET case
253 can be overridden by making sure this option follows the destination parameter.
260 is available instead of the
262 qualifier because non-continuous masks are not allowed in IPv6.
265 specifies network mask of
266 .Li ffff:ffff:0000:0000:0000:0000:0000:0000
268 The default value of prefixlen is 64 to get along with
269 the aggregatable address.
273 Note that the qualifier works only for
277 Routes have associated flags which influence operation of the protocols
278 when sending to destinations matched by the routes.
279 These flags may be set (or sometimes cleared)
280 by indicating the following corresponding modifiers:
282 -xresolve RTF_XRESOLVE - emit mesg on use (for external lookup)
283 -iface ~RTF_GATEWAY - destination is directly reachable
284 -static RTF_STATIC - manually added route
285 -nostatic ~RTF_STATIC - pretend route added by kernel or daemon
286 -reject RTF_REJECT - emit an ICMP unreachable when matched
287 -blackhole RTF_BLACKHOLE - silently discard pkts (during updates)
288 -proto1 RTF_PROTO1 - set protocol specific routing flag #1
289 -proto2 RTF_PROTO2 - set protocol specific routing flag #2
292 The optional modifiers
302 provide initial values to quantities maintained in the routing entry
303 by transport level protocols, such as TCP or TP4.
304 These may be individually locked by preceding each such modifier to
308 meta-modifier, or one can
309 specify that all ensuing metrics may be locked by the
317 command where the destination and gateway are not sufficient to specify
320 case where several interfaces may have the
325 modifiers may be used to determine the interface or interface address.
327 All symbolic names specified for a
331 are looked up first as a host name using
332 .Xr gethostbyname 3 .
333 If this lookup fails,
335 is then used to interpret the name as that of a network.
339 utility uses a routing socket and the new message types
340 .Dv RTM_ADD , RTM_DELETE , RTM_GET ,
343 As such, only the super-user may modify
349 .It "add [host \&| network ] %s: gateway %s flags %x"
350 The specified route is being added to the tables.
352 values printed are from the routing table entry supplied
356 If the gateway address used was not the primary address of the gateway
357 (the first one returned by
358 .Xr gethostbyname 3 ) ,
359 the gateway address is printed numerically as well as symbolically.
360 .It "delete [ host \&| network ] %s: gateway %s flags %x"
361 As above, but when deleting an entry.
365 command is specified, each routing table entry deleted
366 is indicated with a message of this form.
367 .It "Network is unreachable"
368 An attempt to add a route failed because the gateway listed was not
369 on a directly-connected network.
370 The next-hop gateway must be given.
372 A delete operation was attempted for an entry which
373 was not present in the tables.
374 .It "routing table overflow"
375 An add operation was attempted, but the system was
376 low on resources and was unable to allocate memory
377 to create the new entry.
378 .It "gateway uses the same route"
381 operation resulted in a route whose gateway uses the
382 same route as the one being changed.
383 The next-hop gateway should be reachable through a different route.
399 The first paragraph may have slightly exaggerated
403 Currently, routes with the
405 flag set need to have the gateway set to an instance of the
409 option, for the flag to have any effect; unless IP fast forwarding
410 is enabled, in which case the meaning of the flag will always