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       route - show / manipulate the IP routing table


       route [-CFvnee]

       route  [-v]  [-A  family]  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]  del [-net|-host] target [gw Gw] [netmask Nm]
              [metric N] [[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).

       -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 IP addresses in
              dotted decimal or host/network names.

       -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.

       mss M  set the TCP Maximum Segment Size (MSS) for connections over this
              route to M bytes.  The default is the device MTU minus  headers,
              or  a  lower  MTU when path mtu discovery occurred. This setting
              can be used to force smaller TCP packets on the other  end  when
              path   mtu   discovery   does   not  work  (usually  because  of
              misconfigured firewalls that block ICMP Fragmentation Needed)

       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 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 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 add default gw mango-gw
              adds  a  default  route  (which  will  be used if no other route
              matches).  All  packets  using  this  route  will  be  gatewayed
              through  "mango-gw".  The device which will actually be used for
              that route depends on how we can reach "mango-gw" -  the  static
              route to "mango-gw" will have to be set up before.

       route add ipx4 sl0
              Adds  the  route  to  the  "ipx4"  host  via  the SLIP interface
              (assuming that "ipx4" is the SLIP host).

       route add -net netmask gw ipx4
              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 reject
              This  installs  a  rejecting  route  for  the  private   network


       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). It is
              not used by  recent  kernels,  but  may  be  needed  by  routing

       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)


       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 <>.