route - show / manipulate the IP routing table


   route [-CFvnNee] [-A family |-4|-6]

   route  [-v] [-A family |-4|-6] add [-net|-host] target [netmask Nm] [gw
          Gw] [metric N] [mss M] [window W] [irtt I] [reject] [mod]  [dyn]
          [reinstate] [[dev] If]

   route  [-v] [-A family |-4|-6] del [-net|-host] target [gw Gw] [netmask
          Nm] [metric M] [[dev] If]

   route  [-V] [--version] [-h] [--help]


   Route manipulates the kernel's IP routing tables.  Its primary  use  is
   to  set up static routes to specific hosts or networks via an interface
   after it has been configured with the ifconfig(8) program.

   When the add or del  options  are  used,  route  modifies  the  routing
   tables.   Without these options, route displays the current contents of
   the routing tables.


   -A family
          use the specified address family (eg `inet'). Use  route  --help
          for  a  full list. You can use -6 as an alias for --inet6 and -4
          as an alias for -A inet

   -F     operate  on  the  kernel's  FIB  (Forwarding  Information  Base)
          routing table.  This is the default.

   -C     operate on the kernel's routing cache.

   -v     select verbose operation.

   -n     show numerical addresses instead of trying to determine symbolic
          host names. This is useful if you are trying  to  determine  why
          the route to your nameserver has vanished.

   -e     use  netstat(8)-format  for  displaying  the routing table.  -ee
          will generate a very long line  with  all  parameters  from  the
          routing table.

   del    delete a route.

   add    add a new route.

   target the destination network or host. You can provide an addresses or
          symbolic network or host name. Optionally you can use /prefixlen
          notation instead of using the netmask option.

   -net   the target is a network.

   -host  the target is a host.

   netmask NM
          when adding a network route, the netmask to be used.

   gw GW  route packets via a gateway.
          NOTE:  The  specified  gateway  must  be  reachable  first. This
          usually means that you have to set up  a  static  route  to  the
          gateway  beforehand.  If  you specify the address of one of your
          local interfaces, it will be used to decide about the  interface
          to  which  the  packets  should  be  routed to. This is a BSDism
          compatibility hack.

   metric M
          set the metric field in  the  routing  table  (used  by  routing
          daemons)  to  M.  If this option is not specified the metric for
          inet6 (IPv6) address family defaults to '1', for inet (IPv4)  it
          defaults  to  '0'.  You should always specify an explicit metric
          value to not rely on those defaults  -  they  also  differ  from

   mss M  sets  MTU  (Maximum  Transmission Unit) of the route to M bytes.
          Note that the current implementation of the route  command  does
          not allow the option to set the Maximum Segment Size (MSS).

   window W
          set  the  TCP  window  size for connections over this route to W
          bytes. This is typically only used on AX.25  networks  and  with
          drivers unable to handle back to back frames.

   irtt I set  the initial round trip time (irtt) for TCP connections over
          this route to I milliseconds (1-12000). This is  typically  only
          used on AX.25 networks. If omitted the RFC 1122 default of 300ms
          is used.

   reject install a blocking route, which will force  a  route  lookup  to
          fail.   This  is  for  example  used to mask out networks before
          using the default route. This is NOT for firewalling.

   mod, dyn, reinstate
          install a  dynamic  or  modified  route.  These  flags  are  for
          diagnostic  purposes,  and  are  generally  only  set by routing

   dev If force the route to be associated with the specified  device,  as
          the kernel will otherwise try to determine the device on its own
          (by checking already existing routes and device  specifications,
          and  where  the  route is added to). In most normal networks you
          won't need this.

          If dev If is the last option on the command line, the  word  dev
          may  be omitted, as it's the default. Otherwise the order of the
          route modifiers (metric netmask gw dev) doesn't matter.


   route add -net netmask metric 1024 dev lo
          adds the normal loopback  entry,  using  netmask  and
          associated  with  the  "lo"  device  (assuming  this  device was
          previously set up correctly with ifconfig(8)).

   route add -net netmask metric 1024 dev eth0
          adds a route to the local network 192.56.76.x via  "eth0".   The
          word "dev" can be omitted here.

   route del default
          deletes the current default route, which is labeled "default" or
 in the destination field of the current routing table.

   route del -net netmask
          deletes the route. Since the Linux routing kernel uses classless
          addressing,  you  pretty much always have to specify the netmask
          that is same as as seen in 'route -n' listing.

   route add default gw mango
          adds a default route (which will  be  used  if  no  other  route
          matches).   All  packets  using  this  route  will  be gatewayed
          through the address of a node named "mango".  The  device  which
          will actually be used for that route depends on how we can reach
          "mango" - "mango" must be on directly reachable route.

   route add mango sl0
          Adds the route to the host named "mango" via the SLIP  interface
          (assuming that "mango" is the SLIP host).

   route add -net netmask gw mango
          This  command adds the net "192.57.66.x" to be gatewayed through
          the former route to the SLIP interface.

   route add -net netmask dev eth0
          This is an obscure one documented so people know how to  do  it.
          This  sets  all  of  the class D (multicast) IP routes to go via
          "eth0". This is the correct normal  configuration  line  with  a
          multicasting kernel.

   route add -net netmask metric 1024 reject
          This   installs  a  rejecting  route  for  the  private  network

   route -6 add 2001:0002::/48 metric 1 dev eth0
          This adds a IPv6 route with the specified metric to be  directly
          reachable via eth0.


   The  output  of  the kernel routing table is organized in the following

          The destination network or destination host.

          The gateway address or '*' if none set.

          The netmask for the destination  net;  ''  for  a
          host destination and '' for the default route.

   Flags  Possible flags include
          U (route is up)
          H (target is a host)
          G (use gateway)
          R (reinstate route for dynamic routing)
          D (dynamically installed by daemon or redirect)
          M (modified from routing daemon or redirect)
          A (installed by addrconf)
          C (cache entry)
          !  (reject route)

   Metric The 'distance' to the target (usually counted in hops).

   Ref    Number  of  references  to  this  route.  (Not used in the Linux

   Use    Count of lookups for the route.  Depending on the use of -F  and
          -C this will be either route cache misses (-F) or hits (-C).

   Iface  Interface to which packets for this route will be sent.

   MSS    Default  maximum  segment  size  for  TCP  connections over this

   Window Default window size for TCP connections over this route.

   irtt   Initial RTT (Round Trip Time). The kernel  uses  this  to  guess
          about  the  best  TCP  protocol  parameters  without  waiting on
          (possibly slow) answers.

   HH (cached only)
          The number of ARP entries and cached routes that  refer  to  the
          hardware header cache for the cached route. This will be -1 if a
          hardware address is not needed for the interface of  the  cached
          route (e.g. lo).

   Arp (cached only)
          Whether  or  not the hardware address for the cached route is up
          to date.




   ifconfig(8), netstat(8), arp(8), rarp(8), ip(8)


   Route for  Linux  was  originally  written  by  Fred  N.   van  Kempen,
   <>  and  then modified by Johannes Stille and
   Linus Torvalds for pl15. Alan Cox added the mss and window options  for
   Linux   1.1.22.  irtt  support  and  merged  with  netstat  from  Bernd


   Currently maintained by Phil Blundell  <>  and
   Bernd Eckenfels <>.


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