PowerScale: Tips to configure LACP on Nexus switches

Nexus Operating System (NX-OS)

The following settings should be disabled on Cisco Nexus switches when configuring the Link Aggregation Control Protocol (LACP).

lacp suspend-individual
lacp graceful-convergence

LACP SUSPEND-INDIVIDUAL

This setting is enabled by default on port channel configurations for NEXUS switches. The setting tells the switchport to go in to SUSPEND mode if there are no LACP Protocol Data Unit (PDU) received at the switchport. That is, if for any reason, the PowerScale node is not sending LACP PDUs. This setting is required for switch-to-switch configurations but does not make sense for edge devices or server connections.

If LACP is already configured and UP, the switchport may have to be shut down to change from the default enabled to disabled state.

switch# configure terminal
switch(config)# interface port-channel 100
switch(config-if)# no lacp suspend-individual
switch(config-if)#

Consult Cisco guides or Support for more information about this setting.

LACP GRACEFUL-CONVERGENCE

This setting is enabled by default in any port channel configuration that is administratively up. Cisco recommends that this is not enabled for any LACP connected device that is not an NX-OS device.

If LACP is already configured and UP, the switchport may have to be shut down to change from the default enabled to disabled state.

switch# configure terminal
switch(config)# interface port-channel 100
switch(config-if)# no lacp graceful-convergence
switch(config-if)#

Consult Cisco guides or Support for more information about this setting.

Application-Centric Infrastructure (ACI)

An ACI the port channel is created using profiles and policies. A leaf profile is configured for a specific endpoint device, in this case for all PowerScale nodes. The leaf profile brings together other constructs to give the interfaces their personalities.

The following are the interesting components for PowerScale configurations:

• Interface selectors (what interfaces on what switches are in the port channel)
• Interface policy group (how those interfaces behave)
• Individual protocol level policies (tied to the interface policy group)

Each PowerScale node has its own Interface Policy Group which ties in the physical interfaces from the interface selector. As part of the interface policy group, a configuration is mapped to a port channel policy defined under interface policies. If changes are made against the general port channel policy that changes the configuration/behavior for ALL devices using that policy. This should generally be avoided since the interest here is to only affect the PowerScale nodes. Create a new port channel policy, calling it something like "LACP_active_nograceful_nosuspend," which disables the features mentioned above. Assign this policy to each interface policy group in use for PowerScale nodes using LACP in the ACI-mode infrastructure.

Address Resolution Protocol (ARP) FLOODING in ACI Mode

The bridge-domain settings should be applied to all PowerScale nodes, even if LACP is not configured. PowerScale's network operates at layer 2, this is required for network communication. For more information about these settings, see KB 000028116

Additional detailed information about PowerScale Networking can be found in the following document: https://infohub.delltechnologies.com/en-us/t/dell-powerscale-network-design-considerations/

It is important to know if the switches are running in ACI mode or not. The commands and configuration are different in ACI mode. Another important setting is that ARP flooding must be enabled. Issues with IP movement and client connectivity may occur.

Clients disconnect after IP address moves when using Cisco ACI network