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Advantages of Using MC-LAGs to Aggregate FCoE Transit Switch Traffic

 

A multichassis link aggregation group (MC-LAG) reduces operational expenses by providing active-active links with a link aggregation group (LAG), eliminates the need for Spanning Tree Protocol (STP), eliminates a single point-of-failure, and provides faster Layer 2 convergence upon link and device failures.

An MC-LAG adds node-level redundancy to the normal link-level redundancy that a LAG provides. For FCoE transit switch traffic, node-level redundancy enables you to configure a redundant aggregation layer for FCoE traffic, which provides an additional level of flexibility while still supporting the lossless requirements of FCoE traffic across the normally lossy Ethernet network. The redundancy created by configuring an MC-LAG between the QFX Series switches that aggregate FCoE traffic improves storage traffic reliability over the Ethernet network, which reduces network down time and therefore reduces expenses.

An MC-LAG combines two or more physical links into a single logical link between two switches or between a server and a switch. This provides node-level redundancy that improves network efficiency by reducing the effect of link failures and by balancing the load between the devices. If a link fails, the traffic can be forwarded through the other available link, and the logical aggregated link remains in the UP state without interruption.

To take advantage of using an MC-LAG to connect FCoE aggregation layer switches, you need to configure CoS correctly on the aggregation switches and on the transit switches at the FCoE access edge, and design the network topology correctly, including on which switches you enable FIP snooping.