route - manipulate network routing tables

BSD

route [-dnqtv] command [[modifiers] args]
route [-n] command [-net | -host] destination gateway [netmask]

-n numeric address, i.e. do not display names, helpful with DNS problems

-d debug mode, i.e., do not actually modify the routing table.
-t test mode. /dev/null is used instead of a socket.
-n no names for host and networks. (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)
-v verbose
-q quite Suppress all output.

root privilege required for commands in ths rendition.
Only the super-user may modify the routing tables.

commands:

get host display the route for a destination.

route -n get 192.0.43.10 ( example.com )
   route to: 192.0.43.10
destination: default
       mask: default
    gateway: 192.168.1.1 (shows a gateway)
  interface: en1
      flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0      1500         0 

monitor report any changes to the routing information base, routing lookup misses, or suspected network partitionings.
Sleeps wakes and checks,…
add
flush [family] Remove [all] routes.
address families -osi, -xns, -atalk, -inet6, or -inet modifiers, only routes having destinations with addresses in the delineated family will be deleted.
delete
change Change aspects of a route (such as its gateway).
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 destination argument.
-net and -host force the destination.
If the destination has a local address part of INADDR_ANY (0.0.0.0), or
if the 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.
The destination could also be specified in the CIDR net/bits format.

examples:

128.32 -host 128.0.0.32
128.32.130 -host 128.32.0.130
-net 128.32 128.32.0.0
-net 128.32.130 128.32.130.0
192.168.64/20 -net 192.168.64 -netmask 255.255.240.0

A destination default is a synonym for -net 0.0.0.0.

-interface the destination is directly reachable via an interface requiring no intermediary system to act as a gateway.
gateway is the address of this host on the common network, indicating the interface to be used for transmission.
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.

-xns, -osi, and -link specify that all subsequent addresses are in the XNS, OSI, or AppleTalk address families, or are specified as link-level addresses, and the names must be numeric.

-netmask is intended to achieve the effect of an OSI 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). Specify additional address parameter (to be interpreted as a network mask).
In the AF_INET case, the implicit network mask generated can be overridden by making sure this option follows the destination parameter.

For AF_INET6, -prefixlen is available instead of -mask because non-continuous masks are not allowed in IPv6. For example, -prefixlen 32 specifies network mask of 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.
0 is assumed if default is specified.

Flags

     -cloning   RTF_CLONING    - generates a new route on use
     -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
     -llinfo    RTF_LLINFO     - validly translates proto addr to link addr

-rtt, -rttvar, -sendpipe, -recvpipe, -mtu, -hopcount, -expire, and -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 it locked by the -lock meta-modifier, or one can specify that all ensuing metrics may be locked by the -lockrest meta-modifier.

In change or add where the destination and gateway are not sufficient to specify the route (as in the ISO case where several interfaces may have the same address), -ifp or -ifa may be used to determine the interface or interface address.

-proxy specifies that the RTF_LLINFO routing table entry is the published (proxy-only) ARP entry, as reported by arp.

All symbolic names specified for a destination or gateway are looked up first as a host name using gethostbyname.
If this lookup fails, getnetbyname is then used to interpret the name as that of a network.

Route uses a routing socket and the new message types RTM_ADD, RTM_DELETE, RTM_GET, and RTM_CHANGE.

Diagnostics

add [host | network ] %s: gateway %s flags %x The specified route is being added to the tables. The values output are from the routing table entry supplied in the ioctl(2) call.
If the gateway address used was not the primary address of the gateway (the first one returned by gethostbyname(3)), the gateway address is output numerically as well as symbolically.

delete [ host | network ] %s: gateway %s flags %x As above, but when deleting an entry.

%s %s done When the flush command is specified, each routing table entry deleted is indicated with a message of this form.

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.

not in table A delete operation was attempted for an entry which wasn't present in the tables.

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.

gateway uses the same route A 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.

Exits 0 on success, and >0 if an error occurs.

See netintro, arp, routed

4.4BSD June 8, 2001 4.4BSD