ADC

Link redundancy in a cluster with LACP

May 2, 2023

Contributed by:

S C

A NetScaler cluster provides link redundancy for LACP to ensure that all nodes have the same partner key.

To understand the need for link redundancy, let us consider the example of the following cluster setup along with the accompanying cases (with attention to case 3):

Link redundancy

In this setup, interfaces I1, I2, I3, and I4 are bound to the LACP channel with KEY 5. On the partner side, I1 and I2 are connected to Switch 1 to form a single LA channel with KEY 1. Similarly, I3 and I4 are connected to Switch 2 to form a single LA channel with KEY 2.

Now let us consider the following cases to understand the need for link redundancy:

Case 1: Switch 1 is up and Switch 2 is down

In this case, cluster LA on both the nodes would stop receiving LACPDUs from Key2 and would start receiving LACPDUs from Key1. On both the nodes, cluster LA is connected to KEY 1 and I1 and I2 is UP and the channel on both the nodes would be UP.
Case 2: Switch1 goes down and Switch2 becomes UP

In this case, cluster LA on both the nodes would stop receiving LACPDUs from Key1 and would start receiving LACPDUs from Key2. On both the nodes, cluster LA is connected to Key2 and I3 and I4 is UP and the channel on both the nodes would be UP.
Case 3: Both Switch1 and Switch2 are UP

In this case, it is possible that cluster LA on node1 chooses Key1 as its partner and cluster LA on node2 chooses Key2 as its partner. It means that I1 on node1 and I4 on node2 are receiving traffic which is undesirable. It can happen because the LACP state machine is node-level and chooses its partners on first-come first-serve basis.

To solve these concerns, link redundancy of dynamic cluster LA is supported. To configure link redundancy on a channel or interface, you must enable it and optionally specify the threshold throughput as follows:

set channel CLA/1 -linkRedundancy ON -lrMinThroughput <positive_integer>

The throughput of the partner channels is checked against the configured threshold throughput. The partner channel that satisfies the threshold throughput is selected in a first-in-first-out (FIFO) manner. If none of the partner channel meets the threshold, or if threshold throughput is not configured, the partner channel with the maximum number of links is selected.

Note

The threshold throughput can be configured from NetScaler 11 onwards.

The official version of this content is in English. Some of the Cloud Software Group documentation content is machine translated for your convenience only. Cloud Software Group has no control over machine-translated content, which may contain errors, inaccuracies or unsuitable language. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, suitability, or correctness of any translations made from the English original into any other language, or that your Cloud Software Group product or service conforms to any machine translated content, and any warranty provided under the applicable end user license agreement or terms of service, or any other agreement with Cloud Software Group, that the product or service conforms with any documentation shall not apply to the extent that such documentation has been machine translated. Cloud Software Group will not be held responsible for any damage or issues that may arise from using machine-translated content.

Was this helpful

Link redundancy in a cluster with LACP

May 2, 2023

Contributed by:

S C

May 2, 2023

Contributed by:

S C

Link redundancy in a cluster with LACP

In this article