route

The route command is used on Linux systems at the terminal. This information was obtained from a Kali Linux distribution using man route. To see how this command is used on Windows systems, please refer to this page.

NAME  

route – show / manipulate the IP routing table

SYNOPSIS  

       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]

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 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.

OPTIONS

  
-A familyuse 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
-Foperate 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.
-nshow 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.
-euse netstat(8)-format for displaying the routing table.
-ee will generate a very long line with all parameters
from the routing table.
deldelete a route.
addadd a new route.
targetthe 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.
-netthe target is a network.
-hostthe target is a host.
netmask NMwhen adding a network route, the netmask to be used.
gw GWroute 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 Mset 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 Wset 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 Iset 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.
rejectinstall 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, reinstateinstall a dynamic or modified route. These flags are for
diagnostic purposes, and are generally only set by routing
daemons.
dev Ifforce 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.

EXAMPLES  

       route add -net 127.0.0.0 netmask 255.0.0.0 metric 1024 dev lo
              adds the normal loopback entry, using netmask 255.0.0.0
              and associated with the "lo" device (assuming this device
              was previously set up correctly with ifconfig(8)).

       route add -net 192.56.76.0 netmask 255.255.255.0 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 0.0.0.0 in the destination field of the
              current routing table.

       route del -net 192.56.76.0 netmask 255.255.255.0
              deletes the route. Since the Linux routing kernel
              uses classless addressing, you pretty much have to specify the netmask 
              that is same 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 192.57.66.0 netmask 255.255.255.0 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 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 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.

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 destination 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).

       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.

FILES

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

HISTORY

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.

AUTHOR

Currently maintained by Phil Blundell and Bernd Eckenfels.


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