Finally document the net.link.ether.bridge_cfg and

net.link.ether.bridge_refresh variables.  While I'm here, try to
make some of the markup on this page more consistent with the
new (markup-reviewed) content.

PR:		22060
Reviewed by:	ru (for markup, on an earlier version of this delta)
MFC after:	2 days

share/man/man4/bridge.4

@@ -10,40 +10,77 @@
 .Sh DESCRIPTION
 Starting from version 2.2.8,
 .Fx
-supports bridging on ethernet-type
+supports bridging on Ethernet-type
 interfaces.
-This is achieved using the following option
-.Bd -literal
-    options BRIDGE
-.Ed
+This is enabled by including the following line in the kernel configuration
+file:
 .Pp
-in the kernel config file, and is controlled by two
-.Nm sysctl
-variables:
-.Bd -literal
-    net.link.ether.bridge
-.Ed
+.Dl "options BRIDGE"
 .Pp
-Set to 1 to enable bridging, set to 0 to disable it
-.Bd -literal
-    net.link.ether.bridge_ipfw
-.Ed
+Runtime operation of the bridge is controlled by several
+.Xr sysctl 8
+variables.
+The
+.Va net.link.ether.bridge
+variable can be set to 
+.Li 1
+to enable bridging, or set to
+.Li 0
+to disable it.
 .Pp
-Set to 1 to enable
-.Nm ipfw
+The
+.Va net.link.ether.bridge_ipfw
+.Xr sysctl 8
+variable can be set to
+.Li 1
+to enable
+.Xr ipfw 8
 filtering on bridged packets.
 Note that
-.Nm ipfw
+.Xr ipfw 8
 rules only apply
 to IP packets.
 Non-IP packets are subject to the default
-.Nm ipfw
+.Xr ipfw 8
 rule
 .Pq number 65535
 which must be an
 .Ar allow
-rule if we want ARP and other non-IP packets to flow through the
+rule if ARP and other non-IP packets need to flow through the
 bridge.
+.Pp
+The bridge configuration is controlled by the
+.Va net.link.ether.bridge_cfg
+.Xr sysctl 8
+variable.
+It consists of a comma-separated list of
+.Ar interface : Ns Ar cluster
+pairs, where all interfaces with the same
+.Ar cluster 
+number will
+be bridged together.
+.Pp
+Another
+.Xr sysctl 8
+variable reinitializes the bridge; this is required if bridged
+configurations include loadable interfaces.
+After loading new interface drivers, setting the
+.Va net.link.ether.bridge_refresh
+variable to
+.Li 1
+will cause the bridge to reinitialize itself.
+.Sh EXAMPLES
+The following command will cause the
+.Li ep0
+and
+.Li fxp0
+interfaces to be bridged together, and the
+.Li fxp1
+and
+.Li de0 
+interfaces to be bridged together:
+.Pp
+.Dl "sysctl -w net.link.ether.bridge_cfg ep0:0,fxp0:0,fxp1:1,de0:1"
 .Sh BUGS
 Care must be taken not to construct loops in the bridge topology.
 The kernel supports only a primitive form of loop detection, by disabling