User Manual

8-Port or 16-Port Gigabit Smart Managed Pro Switch Model GS418TPP, GS510TLP, and GS510TPP
Configure Switching User Manual215
Configure Layer 2 loop protection
Loops inside a network are costly because they consume resources and reduce the
performance of the network. Detecting loops manually can be cumbersome.
The switch can automatically identify loops in the network. You can enable loop protection
per port or globally.
If loop protection is enabled, the switch sends predefined PDU packets to a Layer 2 multicast
destination address (09:00:09:09:13:A6) on all ports for which the feature is enabled. You
can selectively disable PDU packet transmission for loop protection on specific ports even
while port loop protection is enabled. If the switch receives a packet with the previously
mentioned multicast destination address, the source MAC address in the packet is compared
with the MAC address of the switch. If the MAC address does not match, the packet is
forwarded to all ports that are members of the same VLAN, just like any other multicast
packet. The packet is not forwarded to the port from which it was received.
If the source MAC address matches the MAC address of the switch, the switch can perform
one of the following actions, depending on how you configure the action:
• The port is shut down.
• A log message is generated. (If a syslog server is configured, the log message can be
sent to the syslog server
.)
• The port is shut down and a log message is generated.
If loop protection is disabled, the multicast packet is silently dropped.
Loop protection is not intended for ports that serve as uplinks between spanning tree–aware
switches. It is intended for unmanaged switches that drop spanning tree BPDUs. Loop
protection detects physical and logical loops between Ethernet ports on a device.
You must
enable loop protection globally before you can enable and configure it at the interface level.
Loop protection is supported on physical interfaces and static LAG interfaces, but not on
dynamic LAG interfaces.
Configure global Layer 2 loop protection
To configure L2 loop protection globally:
1. Connect your computer to the same network as the switch.
You can use a WiFi or wired connection to connect your computer to the network, or
connect directly to a switch that is off-network using an Ethernet cable.
2. Launch a web browser.
3. In the address field of your web browser, enter the IP address of the switch.
If you do not know the IP address of the switch, see
Change the default IP address of
the switch on page 13.
The login window opens.