Port loopback detection configuration notes
- Loopback detection packets are sent and received on both tagged and untagged ports. Therefore, this feature cannot be used to detect a loop across separate devices.
The following information applies to Loose Mode loop detection:
- With Loose Mode, two ports of a loop are disabled.
- Different VLANs may disable different ports. A disabled port affects every VLAN using it.
- Loose Mode floods test packets to the entire VLAN. This can impact system performance if too many VLANs are configured for Loose Mode loop detection.
Note:
RUCKUS recommends that you limit the use of Loose Mode. If you have a large number of VLANS,
configuring loop detection on all of them can significantly affect system performance
because of the flooding of test packets to all configured VLANs. An alternative to
configuring loop detection in a VLAN-group of many VLANs is to configure a separate
VLAN with the same tagged port and configuration, and enable loop detection on this
VLAN only.
Note:
When loop detection is used with Layer 2 loop prevention protocols, such as spanning
tree (STP), the Layer 2 protocol takes higher priority. Loop detection cannot send
or receive probe packets if ports are blocked by Layer 2 protocols, so it does not
detect Layer 2 loops when STP is running because loops within a VLAN have been prevented
by STP. Loop detection running in Loose Mode can detect and break Layer 3 loops because
STP cannot prevent loops across different VLANs. In these instances, the ports are
not blocked and loop detection is able to send out probe packets in one VLAN and receive
packets in another VLAN. In this way, loop detection running in Loose Mode disables
both ingress and egress ports.