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Quick links About
route
Syntax
Examples
Related commands
Linux / Unix main page
About route
Show / manipulate the IP routing table.
Syntax
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]
| -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-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 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 -n
Shows routing table for all IPs bound to the server.
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 modifier is not really necessary here because
192.* is a Class C IP address. The word "dev" can be omitted here.
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.
Related commands
arp
ifconfig
netstat
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