1.\" 2.\" $FreeBSD$ 3.\" 4.Dd Sep 28, 1998 5.Dt BRIDGE 4 6.Os 7.Sh NAME 8.Nm bridge 9.Nd Bridging support 10.Sh DESCRIPTION 11Starting from version 2.2.8, FreeBSD supports bridging on ethernet-type 12interfaces. This is achieved using the following option 13.Bd -literal 14 options BRIDGE 15.Ed 16 17in the kernel config file, and is controlled by two 18.Nm sysctl 19variables: 20.Bd -literal 21 net.link.ether.bridge 22.Ed 23 24Set to 1 to enable bridging, set to 0 to disable it 25.Bd -literal 26 net.link.ether.bridge_ipfw 27.Ed 28 29Set to 1 to enable 30.Nm ipfw 31filtering on bridged packets. Note that 32.Nm ipfw 33rules only apply 34to IP packets. Non-IP packets are subject to the default 35.Nm ipfw 36rule 37.Pq number 65535 38which must be an 39.Ar allow 40rule if we want ARP and other non-IP packets to flow through the 41bridge. 42 43 44.Sh BUGS 45.Pp 46Care must be taken not to construct loops in the bridge topology. 47The kernel supports only a primitive form of loop detection, by disabling 48some interfaces when a loop is detected. No support for a daemon running the 49spanning tree algorithm is currently provided. 50.Pp 51With bridging active, interfaces are in promiscuous mode, 52thus causing some load on the system to receive and filter 53out undesired traffic. 54.Pp 55Extended functionality to enable bridging selectively on clusters 56of interfaces is still in the works. 57.Pp 58Not all interface support bridging -- at the moment it works for 59.Dq ed , 60.Dq de , 61.Dq ep , 62.Dq fe , 63.Dq fxp , 64.Dq lnc , 65.Dq mx , 66.Dq tx , 67and 68.Dq xl 69interfaces. 70.Sh SEE ALSO 71.Xr ip 4 , 72.Xr ipfw 8 , 73.Xr sysctl 8 . 74.Sh HISTORY 75.Nm 76bridging was introduced in FreeBSD 2.2.8 77by 78.An Luigi Rizzo Aq luigi@iet.unipi.it . 79