68 Dell Converged Enhanced Ethernet Administrator’s Guide53-1002116-01Link aggregation overview7Link Aggregation Control ProtocolLink Aggregation Control Protocol (LACP) is an IEEE 802.3ad standards-based protocol that allowstwo partner systems to dynamically negotiate attributes of physical links between them to formlogical trunks. LACP determines whether a link can be aggregated into a LAG. If a link can beaggregated into a LAG, LACP puts the link into the LAG. All links in a LAG inherit the sameadministrative characteristics. LACP operates in two modes:• Passive mode—LACP responds to Link Aggregation Control Protocol Data Units (LACPDUs)initiated by its partner system but does not initiate the LACPDU exchange.• Active mode—LACP initiates the LACPDU exchange regardless of whether the partner systemsends LACPDUs.Dynamic link aggregationDynamic link aggregation uses LACP to negotiate which links can be added and removed from aLAG. Typically, two partner systems sharing multiple physical Ethernet links can aggregate anumber of those physical links using LACP. LACP creates a LAG on both partner systems andidentifies the LAG by the LAG ID. All links with the same administrative key and all links that areconnected to the same partner switch become members of the LAG. LACP continuously exchangesLACPDUs to monitor the health of each member link.Static link aggregationIn static link aggregation, links are added into a LAG without exchanging LACPDUs between thepartner systems. The distribution and collection of frames on static links is determined by theoperational status and administrative state of the link.Dell-proprietary aggregationDell-proprietary aggregation is similar to standards-based link aggregation but differs in how thetraffic is distributed. It also has additional rules that member links must meet before they areaggregated:• The most important rule requires that there is not a significant difference in the length of thefiber between the member links, and that all member links are part of the same port-group.The ports that belong to port-group 1, port-group 2, and port-group 3 are te0/0 to te0/7, te0/8to te0/15, and te0/16 to te0/23, respectively.• A maximum of four Dell LAGs can be created per port-group.LAG distribution processThe LAG aggregator is associated with the collection and distribution of Ethernet frames. Thecollection and distribution process is required to guarantee the following:• Inserting and capturing control PDUs.• Restricting the traffic of a given conversation to a specific link.• Load balancing between individual links.• Handling dynamic changes in LAG membership.
