How does EtherChannel works ?

EtherChannel is used to bundle multiple interface links into a single logical link. In a single EtherChannel we can add up to 8 interfaces.

  

What is the use of EtherChannel, why do i bundle multiple links into one?

If we have a fast Ethernet switch which has the speed of 100 Mbps per interface (port). Our workload and data stream is increasing day by day. Now what to do if 100 Mbps is not enough to forward our data stream? Simple, sell the fast Ethernet switch on eBay and get one brand new Cisco Gigabit EtherChannel switch. ;)

Replacing the Hardware is not always the best thing to do. What if the same issue happens to a guy who got Gigabit EtherChannel switch? To overcome this problem EtherChannel is used to bundle multiple fast Ethernet interface in to one.

In a fast Ethernet switch speed of an interface is up to 100 Mbps, if we bundle 8 interfaces in to one, we get the total speed of 800 Mbps. In Gigabit EtherChannel a bundle of 8 interfaces gives the speed up to 8 Gbps.

Now what if a single link in an EtherChannel goes down? Nothing happens, still the bundle works fine with the rest of the 7 links (800-100 = 700) which has the speed of 700 Mbps.

Spanning Tree Protocol (STP) considers the bundled EtherChannel has a single link, so link failure inside the bundle doesn’t affect the STP to recalculate the redundancy.

We can create EtherChannel for Layer2 interface and also for Layer3 interface. Configuring method is different. All the interfaces in an EtherChannel must be configured as either Layer 2 or Layer 3 interfaces. All interfaces in an EtherChannel must be in same speed.

How to configure EtherChannel ?