. This is why there is a maximum of eight physical links in an EtherChannel. Chapter 7: Link Aggregation Figure 7-2 shows how packets are distributed according to this method. Notice that the distribution is not always even. This is important to understand, because link usage statistics-especially graphs-will bear it out. Number of physical links Figure 7-2. EtherChannel physical link balancing On an EtherChannel with eight physical links, each link is assigned a single value. On an EtherChannel with six links, two of the links are assigned two values, and the re- maining four links are each assigned one value. This means two of the links (assuming a theoretical perfect distribution) will receive twice as much traffic as the other four. Having an EtherChannel thus does not imply that all links are used equally. Indeed, it should be obvious looking at Figure 7-2 that the only possible way to distribute traffic equally across all links in an EtherChannel (again, assuming a perfect distribution) is to design one with eight, four, or two physical links. Regardless of the information used to determine the link, the method will still hash the value to a number in the range of 0-7, which will be used to assign a link according to this table. You can change the method the switch uses to determine which path to assign. The default behavior is to use the destination MAC address. However, depending on the version of the software and hardware in use, the options may include: The source MAC address The destination MAC address The source and destination MAC addresses The source IP address The destination IP address The source and destination IP addresses The source port The destination port EtherChannel The source and destination ports The reasons for changing the default behavior vary by circumstance. Figure 7-3 shows a relatively common layout: a group of users connected to Switch A reach a group of servers on Switch B through an EtherChannel. By default, the load-balancing method will be based on the destination MAC address