route - show / manipulate the IP routing table
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]
Route manipulates the kernel's IP routing table. 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.
target The destination network or host. You can provide IP addresses in dotted decimal or host/network names.
netmask Nm
modifier specifies the netmask of the route to be
added.
gw Gw Any IP packets for the target network/host will be routed through the specified 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 adress 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. This is normally used only for fine optimisation of routing setups. The default is 536.
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. Both flags are
generally only set by a routing daemon. This is
only for diagnostic purpose.
dev If Forces 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
adds the normal loopback entry, using netmask
255.0.0.0 (class A net, determined 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 modifier 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 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 10.0.0.0 netmask 255.0.0.0 reject This installs a rejecting route for the private network «10.x.x.x."
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 are
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 rederict)
! (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.
Iface Interface to which packets for this route will be
sent.
Window Default window size for TCP connections over this route.
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.
/proc/net/ipv6_route
/proc/net/route
/proc/net/rt_cache
/etc/networks
/etc/hosts
/etc/init.d/network
ifconfig(8), netstat(8), arp(8)
Route for Linux was originally written by Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> 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.
none :)