Configuring Link Aggregation

Link Aggregation groups up to four Ethernet interfaces together forming a single logical link to support greater throughput than a single physical interface could support, this is referred to as a Link Aggregation Group (LAG). This provides the ability to send multi-gigabit traffic between two Ethernet domains. All ports in an aggregate link must be connected to the same switch. The firewall uses a round-robin algorithm for load balancing traffic across the interfaces in a Link Aggregation Group. Link Aggregation also provides a measure of redundancy, in that if one interface in the LAG goes down, the other interfaces remain connected.

Link Aggregation is referred to using different terminology by different vendors, including Port Channel, Ether Channel, Trunk, and Port Grouping.

Link Aggregation Failover

SonicWall provides multiple methods for protecting against loss of connectivity in the case of a link failure, including High Availability (HA), Load Balancing Groups (LB Groups), and now Link Aggregation. If all three of these features are configured on a firewall, the following order of precedence is followed in the case of a link failure:

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High Availability
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Link Aggregation
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Load Balancing Groups

HA takes precedence over Link Aggregation. Because each link in the LAG carries an equal share of the load, the loss of a link on the Active firewall will force a failover to the Idle firewall (if all of its links remain connected). Physical monitoring needs to be configured only on the primary aggregate port.

When Link Aggregation is used with a LB Group, Link Aggregation takes precedence. LB will take over only if all the ports in the aggregate link are down.

Link Aggregation Limitations

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Currently only static addressing is supported for Link Aggregation
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Link Aggregation is supported on SonicWall E-Class appliances only.
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The Link Aggregation Control Protocol (LACP) is currently not supported

Link Aggregation Configuration

To configure Link Aggregation:
1
On the Network > Interfaces page, click the configure icon for the interface that is to be designated the master of the Link Aggregation Group. The Edit Interface dialog displays.
2
Click on the Advanced tab.
3
In the Redundant/Aggregate Ports drop-down menu, select Link Aggregation.
4
The Aggregate Port option is displayed with a check box for each of the currently unassigned interfaces on the firewall. Select up to three other interfaces to assign to the LAG.
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NOTE: After an interface is assigned to a Link Aggregation Group, its configuration is governed by the Link Aggregation master interface and it cannot be configured independently. In the Interface Settings table, the interface's zone is displayed as "Aggregate Port" and the configuration icon is removed.
5
Set the Link Speed for the interface to Auto-Negotiate.
6
Click OK.
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NOTE: Link Aggregation requires a matching configuration on the Switch. The switch's method of load balancing will very depending on the vendor. Consult the documentation for the switch for information on configuring Link Aggregation. Remember that it may be referred to as Port Channel, Ether Channel, Trunk, or Port Grouping.