The first one (LACP) is preferred as it’s supported by many vendors and it’s a better protocol. These protocols manage the channel establishment between the switches:ġ) Link Aggregation Control Protocol – LACP (IEEE standard protocol)Ģ) Port Aggregation Protocol – PAgP (Cisco Proprietary) By configuring Etherchannel, the bundle is considered as a single logical interface and there are no spanning tree loops. If you connect the interfaces as shown above without configuring EtherChannel, then a Spanning-tree loop will be detected and 3 out of 4 links will be blocked by Spanning-Tree Protocol. This increases bandwidth but also enhances redundancy between the switches.
In our example above, 4x1Gbps interfaces were bundled together thus forming a 4Gbps pipe from users to servers. With Etherchannel, we can bundle together up to 8 interfaces to form a single logical link (Port-Channel) and traffic is load-balanced between all interfaces.
If we connect the two switches together with a single 1Gbps interface, then it could potentially be a bottleneck to traffic from users to servers (especially for high-volume applications). This switch is connected to a Distribution switch which aggregates traffic from several user access switches. The diagram below shows a possible scenario for using Etherchannels:Īssume we have a Data Room switch providing access to servers.
In this article we will describe how to configure both LACP and PAgP EtherChannels on Cisco switches.Īn EtherChannel is a Link Aggregation technology whereby two switches are connected together with multiple interfaces which are bundled together to form a single logical interface (“Port-Channel”) therefore increasing bandwidth between the switches.