Document root_block option

Root_block is also called root port guard, document it.

Signed-off-by: Bastien Roucariès <rouca@debian.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/man/man8/bridge.8 b/man/man8/bridge.8
index 9bfd942f027205a062e2f8a4f174be5c541cdb1e..ff6a5cc906324d622b76ed3b78af61aefe7a405d 100644 (file)
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -372,6 +372,11 @@ enabled on the bridge. By default the flag is off.
 Controls whether a given port is allowed to become root port or not. Only used
 when STP is enabled on the bridge. By default the flag is off.
 
+This feature is also called root port guard.
+If BPDU is received from a leaf (edge) port, it should not
+be elected as root port. This could be used if using STP on a bridge and the downstream bridges are not fully
+trusted; this prevents a hostile guest from rerouting traffic.
+
 .TP
 .BR "learning on " or " learning off "
 Controls whether a given port will learn MAC addresses from received traffic or