[docs] document a little bit more the rationale of the 6bridge script

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@15079 3c298f89-4303-0410-b956-a3cf2f4a3e73

docs/network.tex

@@ -166,6 +166,8 @@ config 6bridge
 
 By default the script bridges the WAN interface with the LAN interface
 and uses ebtables to filter anything that is not IPv6 on the bridge.
+This configuration is particularly useful if your router is not
+IPv6 ND proxy capable (see: http://www.rfc-archive.org/getrfc.php?rfc=4389).
 
 
 IPv6 static addressing is also supported using a similar setup as