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       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

       -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 iproute2.

       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

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

       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

       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 "10.x.x.x."

       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 columns

              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 kernel.)

       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 route.

       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 Eckenfels.


       Currently maintained by Phil  Blundell  <>  and  Bernd  Eckenfels