ZyXEL Communications GS1920v2 Series User Manual page 259

• It will receive its own broadcast messages that it sends out as they loop back. It will then re-broadcast
those messages again.
The following figure shows port
broadcast or multicast packets leave port
they are rebroadcast from B.
Switch in Loop State
Fig ure 185
The loop guard feature checks to see if a loop guard enabled port is connected to a switch in loop
state. This is accomplished by periodically sending a probe packet and seeing if the packet returns on
the same port. If this is the case, the Switch will shut down the port connected to the switch in loop state.
The following figure shows a loop guard enabled port
. Since switch is in loop state, the probe packet
B B
port to ensure that the rest of the network is not affected by the switch in loop state.
N
Loop Guard - Probe Packet
Fig ure 186
The Switch also shuts down port
words loop guard also protects against standard network loops. The following figure illustrates three
switches forming a loop. A sample path of the loop guard probe packet is also shown. In this example,
the probe packet is sent from port
port . The Switch will shut down port
N
Loop Guard - Network Loop
Fig ure 187
Note: After resolving the loop problem on your network you can re-activate the disabled port
via the web configurator (see
Chapter 27 Loop Guard
on switch connected to switch
N A
and reach switch
N
N
returns to port
P
if the probe packet returns to switch
N
and returns on another port. As long as loop guard is enabled on
N
if it detects that the probe packet has returned to the Switch.
N
Section 8.7 on page
GS1920v2 Series User's Guide
259
. Switch is in loop state. When
B B
, they are sent back to port
B
on switch sending a probe packet
A
on . The Switch then shuts down
N A
on any other port. In other
A
85).
on as
N A
to switch
P