Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
By default, a Catalyst 3750 switch that has been configured to use Link Aggregation Control Protocol (LACP) will load balance traffic based on the source Media Access Control (MAC) address of each packet.
LACP is a link-bundling protocol that is defined in the Institute of Electrical and Electronics Engineers (IEEE) 802.3ad standard and can be used to form an EtherChannel link between a Cisco switch and a third-party device, such as a Microsoft Windows Server configured to support network interface card (NIC) teaming. NIC teaming is a feature that uses multiple NICs on a server to function as a single logical link to the network infrastructure. NIC teaming relies on sharing a single Layer 3 address across a bundle of linked Layer 2 interfaces? therefore, NIC teaming is supported only in a Layer 2 access model, not in a Layer 3 access model.
EtherChannel, which is Cisco's name for Ethernet link aggregation, bundles multiple, individual Ethernet links into a single logical link on a switch or router. Packets from the same host device are sent over the same port, and packets from different devices can be sent over different ports. The port-channel load- balance command can be used to modify the load distribution criteria used by EtherChannel. The basic syntax of the port-channel load-balance command is port-channel load-balance {dst-ip | dst-mac | srcdst-ip
|srcdst-mac | src-ip | src-mac}. Issuing the port-channel load-balance src-mac command is the same as issuing the no port-channel load-balance command because src-mac is the default load distribution method.
EtherChannel can aggregate Ethernet links of any speed as long as all of the links in a bundle are the same speed. For example, with Fast EtherChannel, you can configure two FastEthernet links on a switch to connect to two FastEthernet links on a Microsoft Windows Server. The two individual links are treated as a single logical connection by the switch and the server. This doubles the available bandwidth between the router and the switch. Traffic is evenly distributed across both links until one of the physical links fails. If one of the physical links fails, the logical link remains intact and continues to forward traffic.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 3, EtherChannel, p. 88
Cisco: Catalyst 3750 Command Reference: portchannel loadbalance