parprouted [-d] [-p] interface [interface]


parprouted is a daemon for transparent \s-1IP\s0 (Layer 3) proxy \s-1ARP\s0 bridging. Unlike standard bridging, proxy \s-1ARP\s0 bridging allows to bridge Ethernet networks behind wireless nodes. Normal L2 bridging does not work between wireless nodes because wireless does not know about \s-1MAC\s0 addresses used in the wired Ethernet networks. Also this daemon is useful for making transparent firewalls.

The daemon listens for incoming \s-1ARP\s0 requests, and in case the location of the requested \s-1IP\s0 address is unknown, forwards them to other interfaces, as well as updates kernel \s-1ARP\s0 table with the received replies. When necessary, the daemon generates an \s-1ARP\s0 reply itself, which causes the stations to send traffic to the host daemon is running on. By automatically adding appropriate /32 routes to Linux kernel \s-1IP\s0 routing table for the hosts learned via \s-1ARP\s0, daemon ensures that the Linux kernel will be able to route the packets to the destination host when it receives them without any need routing/subnetting manually.

All routes entered by the daemon have a metric of 50.

Unless you use -p switch, all entries in the \s-1ARP\s0 table will be refreshed (rechecked by sending \s-1ARP\s0 requests) every 50 seconds. This keeps them from being expired by kernel.

Normally it takes about 60 ms for a bridge to update all its tables and start sending packets to the destination.


This daemon can be used for unicast traffic only. I.e., \s-1DHCP\s0 is not supported. Use software such as dhcrelay to \*(L"bridge\*(R" \s-1DHCP\s0.

You should have an \s-1IP\s0 address assigned on all of your interfaces that you do bridging on. There is no need for this address to be from the same networks as the bridged networks. Any dummy address will do.

The system should have correct default route.

parprouted requires \*(L"ip\*(R" program from iproute2 tools to be installed in /sbin. If it is installed in another location, please replace \*(L"/sbin/ip\*(R" occurances in the source with the correct path. As well you should have proc filesystem mounted in /proc because the daemon uses /proc/net/arp.

parprouted is designed for and tested only with Linux 2.4.x kernels.


The list of interfaces to do bridging on should be given via the command line.

The daemon accepts the following switches:

-d, which stands for debugging. If you run it in debugging mode the daemon will not go to background and will print additional debugging information to stdout/stderr.

-p, which makes all \s-1ARP\s0 entries to be permanent. This will also result in that \s-1ARP\s0 tables will not be refreshed by \s-1ARP\s0 pings.


To bridge between wlan0 and eth0: parprouted eth0 wlan0


 (C) 2004, Vladimir Ivaschenko <[email protected]>