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ROUTE(8)                   Linux Programmer's Manual                  ROUTE(8)



NAME
       route - show / manipulate the IP routing table


SYNOPSIS
       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]


NOTE
       This program is obsolete. For replacement check ip route.


DESCRIPTION
       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 con-
       figured 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.


OPTIONS
       -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 name-
              server 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 dec-
              imal 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  inter-
              faces,  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  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  pur-
              poses, 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  omit-
              ted, as it's the default. Otherwise the order of the route modifiers (metric
              - netmask - gw - dev) doesn't matter.


EXAMPLES
       route add -net 127.0.0.0
              adds the normal loopback entry, using netmask 255.0.0.0 (class A net, deter-
              mined  from  the  destination  address)  and associated with the "lo" device
              (assuming this device was prviously set up correctly with ifconfig(8)).


       route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0
              adds a route to the network 192.56.76.x via "eth0". The Class C netmask mod-
              ifier  is  not  really necessary here because 192.* is a Class C IP address.
              The word "dev" can be omitted here.


       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 192.57.66.0 netmask 255.255.255.0 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 224.0.0.0 netmask 240.0.0.0 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 10.0.0.0 netmask 255.0.0.0 reject
              This installs a rejecting route for the private network "10.x.x.x."



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

       Destination
              The destination network or destination host.

       Gateway
              The gateway address or '*' if none set.

       Genmask
              The  netmask  for the destination net; '255.255.255.255' for a host destina-
              tion and '0.0.0.0' 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 daemons.

       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 segement 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.



FILES
       /proc/net/ipv6_route
       /proc/net/route
       /proc/net/rt_cache



SEE ALSO
       ip(8)



HISTORY
       Route    for   Linux   was   originally   written   by   Fred   N.    van   Kempen,
       <waltje AT uwalt.org> and then modified by Johannes Stille  and  Linus  Tor-
       valds  for  pl15.  Alan Cox added the mss and window options for Linux 1.1.22. irtt
       support and merged with netstat from Bernd Eckenfels.

AUTHOR
       Currently maintained by Phil Blundell <Philip.Blundell AT pobox.com>.



net-tools                       2 January 2000                        ROUTE(8)

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