132 | Interfacesw w w . d e l l . c o m | s u p p o r t . d e l l . c o m Port Channel Definition and StandardsLink aggregation is defined by IEEE 802.3ad as a method of grouping multiple physical interfaces into asingle logical interface—a link aggregation group (LAG) or port channel. A LAG is “a group of links thatappear to a MAC client as if they were a single link” according to IEEE 802.3ad. In FTOS, a LAG isreferred to as a port channel interface.A port channel provides redundancy by aggregating physical interfaces into one logical interface. If onephysical interface goes down in the port channel, another physical interface carries the traffic.Port Channel BenefitsA port channel interface provides many benefits, including easy management, link redundancy, andsharing.Port channels are transparent to network configurations and can be modified and managed as one interface.For example, you configure one IP address for the group and that IP address is used for all routed traffic onthe port channel.With this feature, you can create larger-capacity interfaces by utilizing a group of lower-speed links. Forexample, you can build a 40-Gigabit interface by aggregating four 10-Gigabit Ethernet interfaces together.If one of the four interfaces fails, traffic is redistributed across the three remaining interfaces.Port Channel ImplementationAn Aggregator supports only port channels that are dynamically configured using the link aggregationcontrol protocol (LACP). For more information, refer to Link Aggregation. Statically-configured portchannels are not supported.Table 10-2 lists the number of port channels per platform.As soon as a port channel is auto-configured, FTOS treats it like a physical interface. For example, IEEE802.1Q tagging is maintained while the physical interface is in the port channel.Member ports of a LAG are added and programmed into hardware in a predictable order based on the portID, instead of in the order in which the ports come up. With this implementation, load balancing yieldspredictable results across switch resets and chassis reloads.A physical interface can belong to only one port channel at a time.Each port channel must contain interfaces of the same interface type/speed.Table 10-2. Number of Port Channels per PlatformPlatform Port-channels Members/ChannelM IO Aggregator 128 16
