ETherChannel

We can implement EtherChannel by bundling multiple physical ports into one or more logical Ether Channel links. The interface speed and type for a single EthernetChannel must be same. The EtherChannel provides maximum 800 Mbps full-duplex speed in case of Fast EtherChannel and or 8 Gbps speed in case of Gigabit EtherChannel between one switch and another switch. We can configure the maximum of eight compatibly-configured Ethernet ports. The Current Cisco IOS switch can support six EtherChannels but, as with the development of new IOSs, the number of the channel including the number of ports may increase.

Originally EtherChannel is developed for increasing the speed on aggregated links between switches. However, now many servers support link aggregation with EtherChannel technology. EtherChannel creates one-to-one connectivity between two devices. It can be configured between two switches or an EtherChannel server and a switch. However, traffic cannot be sent to two different switches through the same EtherChannel link. The individual EtherChannel group member port configuration must be the same on the sides. If the physical ports of one side are configured as trunks, the ports of the other side must also be configured as trunks within the same native VLAN as well as, all ports in each EtherChannel link must be configured as Layer 2 ports.

In the case of layer 3 switches, we can configure layer 3 EtherChannels that will be discussed in a later chapter. A Layer 3 EtherChannel has a single IP address linked with the logical aggregation of switch ports in the Ether Channel.

Each Ether Channel has a logical port-channel interface, illustrated in the figure. A configuration applied to the port-channel interface affects all physical interfaces that are assigned to that interface.

Benefits of EtherChannel

Ether Channel make possible greater speed by merging Fast Ethernet or Gigabit Ethernet ports, of the switch or router as a single port. It uses a Cisco-proprietary hashing algorithm to get this link bonding. Ether Channel was developed by Cisco as a switch-to-switch technique of grouping several Fast Ethernet or Gigabit Ethernet ports into one logical channel. This logical channel is also known as a port channel. The physical interfaces are bundled into a port-channel interface. The benefits and advantages of Ether Channel are as follow:-

  • Most of the configuration is done in the Ether Channel interface instead of individual port, this ensures configuration stability throughout the links.
  • For Ether Channel configuration, no up-gradation is required because it relies on existing switch ports. We can get a faster link connection from the existence of slower links and can get more bandwidth.
  • Load balancing takes place between links that are part of the same Ether Channel. Depending on the hardware platform, one or more load-balancing methods can be implemented. These methods include source MAC to destination MAC load balancing, or source IP to destination IP load balancing, across the physical links.
  • Ether Channel creates an aggregation that is seen as one logical link. When several Ether Channel bundles exist between two switches, STP may block one of the bundles to prevent switching loops. When STP blocks one of the redundant links, it blocks the entire Ether Channel. This blocks all the ports belonging to that Ether Channel link. Where there is only one Ether Channel link, all physical links in the Ether Channel are active because STP sees only one (logical) link.
  • Ether Channel provides redundancy because the overall link is seen as one logical connection. Additionally, the loss of one physical link within the channel does not create a change in the topology; therefore a spanning-tree recalculation is not required. Assuming at least one physical link is present; the Ether Channel remains functional, even if its overall throughput decreases because of a lost link within the Ether Channel.