route.8

来自「Linux下网络相关工具源代码。」· 8 代码 · 共 325 行

.TH ROUTE 8 "8 August 1997" "net-tools" "Linux Programmer's Manual"
.SH NAME
route \- show / manipulate the IP routing table
.SH SYNOPSIS
.B route
.RB [ \-CFvnee ]
.TP
.B route 
.RB [ \-v ]
.RB [ \-A
family] 
.B add 
.RB [ \-net | \-host ] 
target 
.RB [ netmask 
Nm] 
.RB [ gw 
Gw] 
.RB [ metric 
N] 
.RB [ mss 
M] 
.RB [ window 
W] 
.RB [ irtt 
I]
.RB [ reject ]
.RB [ mod ]
.RB [ dyn ] 
.RB [ reinstate ] 
.RB [[ dev ] 
If]
.TP
.B route 
.RB [ \-v ] 
.RB [ \-A
family]
.B del 
.RB [ \-net | \-host ] 
target 
.RB [ gw 
Gw] 
.RB [ netmask 
Nm] 
.RB [ metric 
N] 
.RB [[ dev ]
If]
.TP
.B route 
.RB [ \-V ] 
.RB [ \-\-version ]
.RB [ \-h ]
.RB [ \--help ]
.SH DESCRIPTION
.B 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
.BR ifconfig (8)
program.


.SH OPTIONS
.TP
.B \-v
select verbose operation.

.TP
.B \-A family
Use the specified address family (eg `inet', `inet6').

.TP
.B \-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.

.TP
.B \-e
use
.BR netstat (8)-format
for displaying the routing table.
.B \-ee 
will generate a very long line with all parameters from the routing table.

.TP
.B \-net
the
.B target
is a network.

.TP
.B -host
the
.B target 
is a host.

.TP 
.B -F
displays the kernel FIB routing table. The layout can be changed with
.B \-e
and
.B \-ee
.

.TP 
.B -C
displays the kernel's route cache. 

.TP
.B del
deletes a route.

.TP 
.B add 
adds a route.

.TP
.B target
The destination network or host. You can provide IP addresses in dotted
decimal or host/network names.

.TP
.B netmask Nm
modifier specifies the netmask of the route to be added.

.TP
.B gw Gw
Any IP packets for the target network/host will be routed through the 
specified gateway. 
.B 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.

.TP
.B metric M
Set the metric field in the routing table (used by routing daemons) to M.

.TP 
.B 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.

.TP 
.B 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.

.TP
.B 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.

.TP
.B 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.

.TP
.B 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.

.TP
.B 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 
.B dev If
is the last option on the command line, the word 
.B dev
may be omitted, as it's the default. Otherwise the order of the route
modifiers (metric - netmask - gw - dev) doesn't matter.

.SH EXAMPLES
.TP
.B 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
.BR ifconfig (8)). 

.TP 
.B 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. 

.TP
.B 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. 

.TP
.B route add ipx4 sl0
Adds the route to the "ipx4" host via the SLIP interface (assuming that
"ipx4" is the SLIP host).

.TP
.B 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.

.TP
.B 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. 

.TP
.B 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."

.LP
.SH OUTPUT
The output of the kernel routing table is organized in the following columns
.TP
.B Destination     
The destination network or destination host.
.TP
.B Gateway
The gateway address or '*' if none set.
.TP
.B Genmask         
The netmask for the destination net; '255.255.255.255' for a host destination
and '0.0.0.0' for the 
.B default
route.
.TP
.B Flags 
Possible flags are
.br
.B U
(route is
.BR up )
.br
.B H
(target is a
.BR host )
.br
.B G
(use
.BR gateway )
.br
.B R
.RB ( reinstate
route for dynamic routing)
.br
.B D
.RB ( dynamically
installed by daemon or redirect)
.br
.B M
.RB ( modified
from routing daemon or rederict)
.br
.B !
.RB ( reject
route)
.TP
.B Metric 
The 'distance' to the target (usually counted in hops). It is not used by
recent kernels, but may be needed by routing daemons.
.TP
.B Ref    
Number of references to this route. (Not used in the Linux kernel.)
.TP
.B 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).
.TP
.B Iface
Interface to which packets for this route will be sent.
.TP
.B MSS 
Default maximum segement size for TCP connections over this route.
.TP
.B Window  
Default window size for TCP connections over this route.
.TP
.B irtt
Initial RTT (Round Trip Time). The kernel uses this to guess about the best
TCP protocol parameters without waiting on (possible slow) answers.
.TP
.B 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).
.TP
.B Arp (cached only)
Whether or not the hardware address for the cached route is up to date.
.LP
.SH FILES
.I /proc/net/ipv6_route
.br
.I /proc/net/route
.br
.I /proc/net/rt_cache
.LP
.SH SEE ALSO
.I ifconfig(8), netstat(8), arp(8), rarp(8)
.LP
.SH HISTORY
.B Route
for Linux was originally written by Fred N.  van Kempen,
<[e-mail]> 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.
.SH AUTHOR
Currently maintained by Phil Blundell <[e-mail]>.