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ROUTE !!!ROUTE NAME SYNOPSIS DESCRIPTION OPTIONS EXAMPLES OUTPUT FILES SEE ALSO HISTORY AUTHOR ---- !!NAME route - show / manipulate the IP routing table !!SYNOPSIS __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__] !!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). __-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 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 occured. 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 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 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 __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 __route add ipx4 sl0__ Adds the route to the __route add -net 192.57.66.0 netmask 255.255.255.0 gw ipx4__ This command adds the net __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 __route add -net 10.0.0.0 netmask 255.0.0.0 reject__ This installs a rejecting route for the private network !!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). It is not used by recent kernels, but may be needed by routing daemons. __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 segement 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'' !!SEE ALSO ''ifconfig(8), netstat(8), arp(8), rarp(8)'' !!HISTORY __Route__ for Linux was originally written by Fred N. van Kempen, __ !!AUTHOR Currently maintained by Phil Blundell ----
12 pages link to
route(8)
:
netstat(8)
Man8r
arp(8)
ifconfig(8)
rarp(8)
ESRCH
proc(5)
NetworkingNotes
interfaces(5)
ThingsToDoWithYourLinuxBox
NetworkingUtilities
route(4)
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