Technical information

AX Series L2 Loop Detection Configuration Guide (Edition 2)

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

The L2 loop detection functionality works when the target device sends and receives an L2 loop detection frame.

However, the transmission rate of L2 loop detection frames required for each device is determined based on the

sending interval of L2 loop detection frames and the number of VLAN ports subject to L2 loop detection. The

number of VLAN ports subject to L2 loop detection is the sum of the products of the number of physical interfaces

subject to L2 loop detection in the L2 loop detection functionality and the number of the VLANs used for the

respective interface.

(A) L2 loop detection frame rate per device (pps) =

Number of VLAN ports subject to L2 loop detection/sending interval of L2 loop detection frame (sec.)

(B) On the other hand, the L2 loop detection frame sending capacity depends on each device. (See the following

table.)

Table 1.4-3 L2 loop detection frame transmission rate

Frame transmission rates (per device)

Model

When using STP, GSRP, or the

Ring Protocol

When not using STP, GSRP, or

the Ring Protocol

All models of the AX6700S/AX6300S series

90 pps (recommended)

600 pps (maximum)

All models of the AX3600S/AX2400S series 30 pps (recommended)

200 pps (maximum)

All models of the AX1200S series 20 pps (maximum)

#1: The transmission rate is automatically adjusted within the maximum value for each device (AX6700S/6300S series: 600

pps; AX3600S/AX2400S series: 200 pps; AX1200S series: 20 pps) according to the above-mentioned equation.

#2: When using STP, GSRP, or the Ring Protocol, set the transmission rate to the recommended value or less. If the

transmission rate is any higher, normal operation of STP, GSRP, or the Ring Protocol is not guaranteed.

#3: Frames that exceed the maximum value will not be sent. Loop failures cannot be detected on target ports or VLANs from

which frames have not been sent. Make sure that you set the transmission interval to achieve a transmission rate of no more

than the maximum value.

Accordingly, parameter (A) (the number of physical interfaces to be used, the number of VLANs, and the

sending interval) must be set so that (A) is less than or equal to (B). But it must eventually be adjusted using the

sending interval of L2 loop detection frames if the required device and the number of its physical interfaces and the

number of VLANs are determined by the network configuration or other factors.

This can be calculated by transforming the above-mentioned equation as follows:

Sending interval of L2 loop detection frame (sec.) ≥

Number of VLAN ports subject to L2 loop detection/frame transmission rate per device (pps)

As the time required for L2 loop detection is determined depending on this sending interval of the L2 loop

detection frame, it is preferred to set a value as small as possible within the range that satisfies the above inequality.

Example:

If one trunk port containing 19 access ports (with a VLAN) and 3 VLANs are used as the target of L2 loop

detection on an AX2400S series switch that uses STP:

For the sending interval of an L2 loop detection frame:

(19 x 1 + 1 x 3) / 30 (from Table 1.4-2) = 22 / 30 = 0.7333...

Based on this calculation, ALAXALA Networks Corporation recommends that you set a value of 1 (sec.).