# route

## 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** _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 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
                  firewalling.
    
           **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.
    


## 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 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 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_
    


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