Better documentation of BDPU guard

Document that guard disable the port and how to reenable 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 bd33635ad2973bb72da6873b149f7f49b12c3153..9bfd942f027205a062e2f8a4f174be5c541cdb1e 100644 (file)
--- a/man/man8/bridge.8
+++ b/man/man8/bridge.8
@@ -340,7 +340,18 @@ STP BPDUs.
 .BR "guard on " or " guard off "
 Controls whether STP BPDUs will be processed by the bridge port. By default,
 the flag is turned off allowed BPDU processing. Turning this flag on will
-cause the port to stop processing STP BPDUs.
+disables
+the bridge port if a STP BPDU packet is received.
+
+If running Spanning Tree on bridge, hostile devices on the network
+may send BPDU on a port and cause network failure. Setting
+.B guard on
+will detect and stop this by disabling the port.
+The port will be restarted if link is brought down, or
+removed and reattached.  For example if guard is enable on
+eth0:
+
+.B ip link set dev eth0 down; ip link set dev eth0 up
 
 .TP
 .BR "hairpin on " or " hairpin off "