Technical information

AX Series L2 Loop Detection Configuration Guide (Edition 2)

2.2 Important points for constructing a system

(1) Set the L2 loop detection functionality on a device located as near as possible to the endpoint, such as an access switch.

As described above:

- L2 redundancy protocols are used as measures against loops on upstream networks such as core networks in

many cases.

- When a port is blocked due to loop detection, devices located further upstream have more impact on

downstream networks.

For these reasons, ALAXALA Networks Corporation recommends that you use the L2 loop detection for a

device as near as possible to the endpoint.

(2) Set uplink-port for ports on the upstream network where L2 redundancy protocols are available.

Setting uplink-port blocks no ports when a control frame for L2 loop detection is sent or when a loop is

detected but receives and detects L2 loop detection frames.

This has no impact on L2 redundancy protocol operations on the upstream network and is effective for the

detection of loops created across devices via the upstream network.

(3) Enable the detection and port block setting (send-inact-port) for ports connected to endpoints such

as terminals and hubs.

Detection of a loop blocks ports, which can prevent loops. This can prevent broadcast storms caused by loops.

(4) As a general rule, specify the L2 loop detection and port blocking setting for empty ports that might be connected to terminals

and hubs.

In particular, if devices are installed in locations easily accessed by general users, it is preferred that you specify

the setting in advance to prevent loops due to incorrect connections.

However, note that even ports in the link-down status are subject to L2 loop detection with this setting, affecting

the sending interval settings of L2 loop detection frames. (For details about the sending interval of L2 loop

detection frames, see 1.4 (4) Transmission rate and sending interval of L2 loop detection frames

in this document

or 3. Switch capacities in the Software Manual Configuration Guide Vol. 1 for each device.)

Therefore, for devices installed in locations not easily accessed by general users, such as data centers, server

rooms, and inside racks, the use of the L2 loop detection functionality should be kept at a minimum level.

(5) Set shutdown for ports not to be used or prohibited.

For reasons similar to the above, if there is a port that is not to be connected or for which connection is prohibited

on a device installed in a location easily accessed by general users, disable (shutdown) the port in the

configuration in advance.

This setting allows for no loops to occur even if the port is improperly connected, because the port will not link

up.