Dell N3200-ON EMC Networking N-Series Switches CLI Reference Guide version 6.6 - Page 671

Port Channel Commands Dell EMC Networking N1100-ON/N1500/N2000/N2100-ON/N2200ON/N3000-ON/N3100-ON/N3200-ON Series Switches A port channel is a set of one or more links that can be aggregated together to form a bonded channel (Link Aggregation Group or LAG or port channel). Individual conversations in a particular direction always travel over a single link in the port channel, however, in aggregate, the bandwidth usage of all of the links is fairly evenly distributed. Port channels have the advantage of allowing incremental bandwidth to be added as needed (by adding additional links) and supporting a form of fault tolerance (traffic on failed links is redistributed among other links in the LAG). LAGs are formed from similarly configured physical links, i.e. the speed, duplex, auto-negotiation, PFC configuration, DCBX configuration, etc. must be compatible on all member links. Per IEEE 802.1AX, only links with the same operational characteristics, such as speed and duplex setting, may be aggregated. Dell EMC Networking switches aggregate links only if they have the same operational speed and duplex setting, as opposed to the configured speed and duplex setting. This allows operators to aggregate links that use auto negotiation to set values for speed and duplex or to aggregate ports with SFP+ technology operating at a lower speeds, e.g., 1G. Dissimilar ports will not become active in the LAG if their operational settings do not match those of the first member of the LAG. In practice, some ports in a LAG may auto-negotiate a different operational speed than other ports depending on the far end settings and any link impairments. Per the above, these ports will not become active members of the LAG. On a reboot or on flapping the LAG links, a lower speed port may be the first port selected to be aggregated into the LAG. In this case, the higher speed ports are not aggregated. Use the lacp port-priority command to select one or more primary link to lead the formation of the aggregation group. While it is a requirement of a LAG that the link members operate at the same duplex and speed settings, administrators should be aware that copper ports have larger latencies than fiber ports. If fiber and copper ports are aggregated together, packets sent over the fiber ports may arrive significantly sooner at the destination than packets sent over the copper ports. This can cause significant issues in the receiving host (e.g. a TCP receiver) as it would be required to buffer a potentially large number of out-of-order frames. Devices Layer 2 Switching Commands 671