NAME

iproute − Internet route table manager

SYNOPSIS

­bind −a #P /net

­/net/iproute

DESCRIPTION

The ­iproute device allows the specification of routes for families of IP addresses.  It maintains a kernel-resident routing table for IP addresses used by TCP, IL and UDP.  Each route consists of a destination IP address, an IP mask, and an IP gateway address.  Every packet sent by the system is routed according to the route table.  An address matches the route table entry when a packet’s destination address matches the table destination address under the mask. When a match is found, the packet is sent to the gateway IP address. If there is no match, the packet is sent with the original destination address.  If there are several matches, the one whose mask has the fewest leading zeroes is chosen.  (Because of the definition of IP masks, this mask preserves the largest portion of the address and is therefore the most specific.)  This is forced by storing the routes in decreasing number of ones order and returning the first match.  The default gateway has no ones in the mask and is thus the last matched. 

Reading ­iproute reports the current routes entered in the table.  Writing control messages to ­iproute edits the table.  Route entries are made by writing a string of format

add ipdest mask ipgateway

Entries are deleted by writing a string of format

delete ipdest mask

The whole table can be cleared by writing the string flush. 

For example, to install a gateway address to accept all IP packets from a machine:

g% echo ’add 0.0.0.0 0.0.0.0 192.20.225.225’ > /net/iproute
g% cat /net/iproute
0.0.0.0 & 0.0.0.0 -> 192.20.225.225

SEE ALSO

ip(3), ipconfig(8)

Plan 9  —  January 03, 1993