route - show / manipulate the IP routing table
- [-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]
- [-v] [-A family |-4|-6]
del [-net|-host] target [gw Gw]
[netmask Nm] [metric M] [[dev]
- [-V] [--version] [-h]
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)
When the add
options are used, route
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
- operate on the kernel's FIB (Forwarding Information Base)
routing table. This is the default.
- operate on the kernel's routing cache.
- select verbose operation.
- 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.
- use netstat(8)-format for displaying the routing
table. -ee will generate a very long line with all parameters from
the routing table.
- delete a route.
- add a new route.
- 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
- the target is a network.
- 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
- 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.
- route add -net 127.0.0.0 netmask 255.0.0.0 metric 1024
- 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 126.96.36.199 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
- 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 188.8.131.52 netmask 255.255.255.0 gw
- This command adds the net "192.57.66.x" to be
gatewayed through the former route to the SLIP interface.
- route add -net 184.108.40.206 netmask 240.0.0.0 dev
- 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
- route add -net 10.0.0.0 netmask 255.0.0.0 metric 1024
- This installs a rejecting route for the private network
- 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; '255.255.255.255' for
a host destination and '0.0.0.0' for the default route.
- 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)
- The 'distance' to the target (usually counted in
- Number of references to this route. (Not used in the Linux
- 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).
- Interface to which packets for this route will be
- Default maximum segment size for TCP connections over this
- Default window size for TCP connections over this
- Initial RTT (Round Trip Time). The kernel uses this to
guess about the best TCP protocol parameters without waiting on (possibly
- 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.
- Arp (cached only)
- Whether or not the hardware address for the cached route is
up to date.
for Linux was originally written by Fred N. van Kempen,
<email@example.com> 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 <Philip.Blundell@pobox.com> and
Bernd Eckenfels <firstname.lastname@example.org>.