Aruba CX Link Aggregation Groups

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  • Post category:Aruba

A Link Aggregation Group (LAG) is used to bundle multiple physical interfaces into one logical link, the benefits of this include: increased bandwidth, with traffic distributed over the member interfaces and improved resiliency, when one interfaces fails traffic continues using the other interface(s).

Multi-Chassis LAGs (MC-LAG) is a LAG with bundled interfaces that terminate on separate physical switches, for the purpose of providing redundancy in the event one of the switch fails. MC-LAGs are used as part of a Virtual Switching Extension (VSX) solution, which enables two Aruba CX switches to appear as a single switch to downstream connected devices. VSX is used in collapsed core or aggregation layer, providing dual-homed connectivity to connected devices and resiliency by eliminating a single point of failure. VSX and MC-LAG are supported on Aruba CX 6400, 8200 and 8300 series switches.

The figure below represents a typical Aruba CX collapsed core design, with both core switches (CORE-1 and CORE-2) configured as a VSX pair. An MC-LAG is configured on both core switches, connecting to a LAG configured on an edge switch (EDGE-1).

Configuration

This post will cover configuration of an MC-LAG on a VSX pair and a LAG on an edge switch.

CORE-1 (VSX Primary)

CORE-1 is configured as the VSX primary switch, where the configuration is synchronised to the VSX peer (CORE-2)

Enable synchronisation of mc-lag interfaces

vsx
 vsx-sync mclag-interfaces

Configure a multi-chassis LAG, ensure the keyword multi-chassis is appended.

interface lag 1 multi-chassis
 description LAG to EDGE-1
 no routing
 no shutdown
 vlan trunk native 999
 vlan trunk allowed 1000,1001
 lacp mode active

Configure the physical interface as a member of the MC-LAG.

interface 1/1/4
 no shutdown
 description Link to EDGE-1 (1/1/1)
 lag 1

CORE-2 (VSX Secondary)

With MC-LAG configuration synchronised from the VSX Primary switch, the interface just needs to be created and the command “no shutdown” on CORE-2.

interface lag 1 multi-chassis
 no shutdown

Configure the physical interface as a member of the MC-LAG.

interface 1/1/4
 no shutdown
 description Link to EDGE-1 (1/1/2)
 lag 1

Edge Switch

A standard LAG needs to be created.

interface lag 1
 description LAG to CORE-1 and CORE-2
 no routing
 no shutdown
 vlan trunk native 999
 vlan trunk allowed 1000,1001
 lacp mode active

Configure the physical interfaces as a member of the LAG.

interface 1/1/1
 no shutdown
 description Link to CORE-1 (1/1/4)
 lag 1
interface 1/1/2
 no shutdown
 description Link to CORE-2 (1/1/4)
 lag 1

Testing

From the edge switch EDGE-1 run the command show interface lag 1. From the output below, we can confirm the status is up, the interfaces in the LAG, native VLAN, allowed VLANs and packet statistics.

From the edge switch EDGE-1 run the command show lacp interface. From the output below, we can confirm the LAG is up, the interfaces in the LAG, the Port ID of the local switch, the Port ID of the remote switch and the local/remote System ID.

From CORE-1 run the command show lacp interface multi-chassis, this command provides the status of multi-chassis LAGs only. From the output below we can confirm the status of CORE-1’s MC-LAG and CORE-2’s (Remote Actor) MC-LAG.

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