 on IOS and CatOS EtherChannels on IOS and NX-OS switches are actually virtual interfaces, and they are referenced like any other interfaces (for example, interface port-channel or int poo). There is another terminology problem that can create many headaches for network administrators. While a group of physical Ethernet links bonded together is called an EtherChannel in Cisco parlance, Unix admins sometimes refer to the same configura- tion as a trunk. Of course, in the Cisco world the term "trunk" refers to something completely different: a link that labels frames with VLAN information SO that multiple VLANs can traverse it. Some modern Unixes sometimes create a bond interface when performing link aggregation, and Windows admins often use the term teaming when combining links. EtherChannel Load Balancing As stated earlier, EtherChannel, by default, does not truly provide the aggregate speed of the included physical links. EtherChannel gives the perceived speed of the combined links by passing certain packets through certain physical links. By default, the physical link used for each packet is determined using the packet's destination MAC address. The algorithm used is Cisco-proprietary, but it is deterministic in that packets with the same destination MAC address will always travel over the same physical link. This ensures that packets sent to a single destination MAC address never arrive out of order. The hashing algorithm for determining the physical link to be used may not be public, but the weighting of the links used in the algorithm is published. What is important here is the fact that a perfect balance between the physical links is not necessarily assured. The hashing algorithm takes the destination MAC address (or another value, as you'll see later), and hashes that value to a number in the range of 0-7. The same range is used regardless of how many links are actually in the EtherChannel. Each physical link is assigned one or more of these eight values, depending on how many links are in the EtherChannel