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. 13This is achieved using the following option 14.Bd -literal 15 options BRIDGE 16.Ed 17 18in the kernel config file, and is controlled by two 19.Nm sysctl 20variables: 21.Bd -literal 22 net.link.ether.bridge 23.Ed 24 25Set to 1 to enable bridging, set to 0 to disable it 26.Bd -literal 27 net.link.ether.bridge_ipfw 28.Ed 29 30Set to 1 to enable 31.Nm ipfw 32filtering on bridged packets. 33Note that 34.Nm ipfw 35rules only apply 36to IP packets. 37Non-IP packets are subject to the default 38.Nm ipfw 39rule 40.Pq number 65535 41which must be an 42.Ar allow 43rule if we want ARP and other non-IP packets to flow through the 44bridge. 45 46 47.Sh BUGS 48.Pp 49Care must be taken not to construct loops in the bridge topology. 50The kernel supports only a primitive form of loop detection, by disabling 51some interfaces when a loop is detected. 52No support for a daemon running the 53spanning tree algorithm is currently provided. 54.Pp 55With bridging active, interfaces are in promiscuous mode, 56thus causing some load on the system to receive and filter 57out undesired traffic. 58.Pp 59Extended functionality to enable bridging selectively on clusters 60of interfaces is still in the works. 61.Pp 62Not all interface support bridging -- at the moment it works for 63.Dq ed , 64.Dq de , 65.Dq ep , 66.Dq fe , 67.Dq fxp , 68.Dq lnc , 69.Dq mx , 70.Dq tx , 71and 72.Dq xl 73interfaces. 74.Sh SEE ALSO 75.Xr ip 4 , 76.Xr ipfw 8 , 77.Xr sysctl 8 . 78.Sh HISTORY 79.Nm 80bridging was introduced in FreeBSD 2.2.8 81by 82.An Luigi Rizzo Aq luigi@iet.unipi.it . 83