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28 .\" @(#)route.8 8.3 (Berkeley) 3/19/94
35 .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
68 address family as family hint for subcommands.
72 address family as family hint for subcommands.
74 Run in debug-only mode, i.e., do not actually modify the routing table.
76 Bypass attempts to print host and network names symbolically
77 when reporting actions.
78 (The process of translating between symbolic
79 names and numerical equivalents can be quite time consuming, and
80 may require correct operation of the network; thus it may be expedient
81 to forget this, especially when attempting to repair networking operations).
83 Run in test-only mode.
85 is used instead of a socket.
87 (verbose) Print additional details.
89 Suppress all output from the
90 .Cm add , change , delete ,
100 utility provides the following commands:
102 .Bl -tag -width Fl -compact
108 Delete a specific route.
114 Change aspects of a route (such as its gateway).
116 Lookup and display the route for a destination.
118 Continuously report any changes to the routing information base,
119 routing lookup misses, or suspected network partitionings.
126 The monitor command has the syntax:
128 .Bd -ragged -offset indent -compact
131 .Cm monitor Op Fl fib Ar number
134 The flush command has the syntax:
136 .Bd -ragged -offset indent -compact
139 .Cm flush Oo Ar family Oc Op Fl fib Ar number
144 command is specified,
146 will ``flush'' the routing tables of all gateway entries.
147 When the address family may is specified by any of the
151 modifiers, only routes having destinations with addresses in the
152 delineated family will be deleted.
157 can be used as aliases for
164 option is specified, the operation will be applied to
168 The add command has the following syntax:
170 .Bd -ragged -offset indent -compact
174 .Op Fl net No \&| Fl host
175 .Ar destination gateway
180 and the other commands have the following syntax:
182 .Bd -ragged -offset indent -compact
186 .Op Fl net No \&| Fl host
188 .Op Ar gateway Op Ar netmask
194 is the destination host or network,
196 is the next-hop intermediary via which packets should be routed.
197 Routes to a particular host may be distinguished from those to
198 a network by interpreting the Internet address specified as the
201 The optional modifiers
205 force the destination to be interpreted as a network or a host, respectively.
209 .Dq local address part
215 is the symbolic name of a network, then the route is
216 assumed to be to a network; otherwise, it is presumed to be a
220 could also be specified in the
221 .Ar net Ns / Ns Ar bits
227 .Fl host Li 128.0.0.32 ;
230 .Fl host Li 128.32.0.130 ;
234 .Fl net Li 128.32.130
240 .Fl net Li 192.168.64 Fl netmask Li 255.255.240.0 .
246 is a synonym for the default route.
250 .Fl net Fl inet Li 0.0.0.0 ,
254 .Fl net Fl inet6 Li :: .
256 If the destination is directly reachable
257 via an interface requiring
258 no intermediary system to act as a gateway, the
260 modifier should be specified;
261 the gateway given is the address of this host on the common network,
262 indicating the interface to be used for transmission.
263 Alternately, if the interface is point to point the name of the interface
264 itself may be given, in which case the route remains valid even
265 if the local or remote addresses change.
270 to achieve the effect of an OSI ESIS
271 redirect with the netmask option,
272 or to manually add subnet routes with
273 netmasks different from that of the implied network interface
274 (as would otherwise be communicated using the OSPF or ISIS routing protocols).
275 One specifies an additional ensuing address parameter
276 (to be interpreted as a network mask).
277 The implicit network mask generated in the AF_INET case
278 can be overridden by making sure this option follows the destination parameter.
285 is available instead of the
287 qualifier because non-continuous masks are not allowed in IPv6.
290 specifies that a network mask of
291 .Li ffff:ffff:0000:0000:0000:0000:0000:0000
293 The default prefixlen is 64.
294 However, it is assumed to be 0 if
298 Note that the qualifier works only for
302 Routes have associated flags which influence operation of the protocols
303 when sending to destinations matched by the routes.
304 These flags may be set (or sometimes cleared)
305 by indicating the following corresponding modifiers:
307 -xresolve RTF_XRESOLVE - emit mesg on use (for external lookup)
308 -iface ~RTF_GATEWAY - destination is directly reachable
309 -static RTF_STATIC - manually added route
310 -nostatic ~RTF_STATIC - pretend route added by kernel or daemon
311 -reject RTF_REJECT - emit an ICMP unreachable when matched
312 -blackhole RTF_BLACKHOLE - silently discard pkts (during updates)
313 -proto1 RTF_PROTO1 - set protocol specific routing flag #1
314 -proto2 RTF_PROTO2 - set protocol specific routing flag #2
317 The optional modifiers
327 provide initial values to quantities maintained in the routing entry
328 by transport level protocols, such as TCP or TP4.
329 These may be individually locked by preceding each such modifier to
333 meta-modifier, or one can
334 specify that all ensuing metrics may be locked by the
340 accepts expiration time of the route as the number of seconds since the
343 When the first character of the number is
347 it is interpreted as a value relative to the current time.
349 The optional modifier
351 specifies that the command will be applied to a non-default FIB.
354 must be smaller than the
358 When this modifier is not specified,
359 or a negative number is specified,
360 the default FIB shown in the
367 allows multiple FIBs by a comma-separeted list and/or range
371 means the FIB number 2, 4, and 6.
373 .Qq Fl fib Li 1,3-5,6
374 means the 1, 3, 4, 5, and 6.
380 command where the destination and gateway are not sufficient to specify
381 the route (as in the ISO case where several interfaces may have the
386 modifiers may be used to determine the interface or interface address.
388 All symbolic names specified for a
392 are looked up first as a host name using
393 .Xr gethostbyname 3 .
394 If this lookup fails,
396 is then used to interpret the name as that of a network.
400 utility uses a routing socket and the new message types
401 .Dv RTM_ADD , RTM_DELETE , RTM_GET ,
404 As such, only the super-user may modify
407 .Fx provides support for scalable multipath routing.
408 It is activated by default, but can be turned off by setting the
409 .Va net.route.multipath
413 There are multiple route lookup algorithms available.
414 They can be configured by setting
415 .Va net.route.algo.inet.algo
417 .Va net.route.algo.inet6.algo
422 A list of available algorithms can be obtained by accessing the
426 .Va net.route.algo.inet.algo_list
428 .Va net.route.algo.inet6.algo_list
431 The following algorithms are available:
432 .Bl -tag -width radix_lockless
434 Base system radix backend.
436 Lockless binary search in a special IP array, tailored for a small FIB
438 This algorithm is only available for IPv4.
440 Lockless immutable radix, re-created on every rtable change,
441 tailored for a small FIB with <1000 routes.
443 DPDK DIR24-8-based lookups, lockless datastructure, optimized
445 DIR24-8 relies on a large flat lookup table (64 MB with IPv4) which is
446 directly indexed by the more significant portion of the lookup key.
447 In order to use the dpdk_lpm algorithm one or both of the
448 following kernel modules must be loaded via
450 .Bl -tag -width dpdk_lpm6.ko -compact
452 DPDK implementation for IPv4.
454 DPDK implementation for IPv6.
457 IPv4 only, lockless, compressed lookup structure
458 (below 2.5 Bytes per IPv4 prefix for large BGP FIBs)
459 which easily fits into modern CPU cache hierarchies,
460 lookup throughput scales linearly with CPU cores.
461 Loadable as a kernel module at runtime or via
463 .Bl -tag -width fib_dxr.ko -compact
468 The algorithms are selected automatically based on the size of the routing
470 They can be changed, but not every algorithm performs best for every
475 Add a default route to the network routing table.
476 This will send all packets for destinations not available in the routing table
477 to the default gateway at 192.168.1.1:
479 .Dl route add -net 0.0.0.0/0 192.168.1.1
481 A shorter version of adding a default route can also be written as:
483 .Dl route add default 192.168.1.1
485 Add a static route to the 172.16.10.0/24 network via the 172.16.1.1 gateway:
487 .Dl route add -net 172.16.10.0/24 172.16.1.1
489 Change the gateway of an already established static route in the routing table:
491 .Dl route change -net 172.16.10.0/24 172.16.1.2
493 Display the route for a destination network:
495 .Dl route show 172.16.10.0
497 Delete a static route from the routing table:
499 .Dl route delete -net 172.16.10.0/24 172.16.1.2
501 Remove all routes from the routing table:
505 The routing table can be listed with
509 .It "add [host \&| network ] %s: gateway %s flags %x"
510 The specified route is being added to the tables.
512 values printed are from the routing table entry supplied
516 If the gateway address used was not the primary address of the gateway
517 (the first one returned by
518 .Xr gethostbyname 3 ) ,
519 the gateway address is printed numerically as well as symbolically.
520 .It "delete [ host \&| network ] %s: gateway %s flags %x"
521 As above, but when deleting an entry.
525 command is specified, each routing table entry deleted
526 is indicated with a message of this form.
527 .It "Network is unreachable"
528 An attempt to add a route failed because the gateway listed was not
529 on a directly-connected network.
530 The next-hop gateway must be given.
532 A delete operation was attempted for an entry which
533 was not present in the tables.
534 .It "routing table overflow"
535 An add operation was attempted, but the system was
536 low on resources and was unable to allocate memory
537 to create the new entry.
538 .It "gateway uses the same route"
541 operation resulted in a route whose gateway uses the
542 same route as the one being changed.
543 The next-hop gateway should be reachable through a different route.
558 The first paragraph may have slightly exaggerated
562 Currently, routes with the
564 flag set need to have the gateway set to an instance of the
568 option, for the flag to have any effect; unless IP fast forwarding
569 is enabled, in which case the meaning of the flag will always