In review, a VLAN is a logical grouping of switch ports that connects nodes of nearly any type, regardless of physical location. VLAN segmentation is based on traffic flow patterns. A VLAN is usually defined as an end-to-end VLAN or a local VLAN. An end-to-end VLAN spans the entire switched network, whereas a local VLAN is limited to the switches in the building access and building distribution submodules. The creation of a VLAN implementation plan depends on the business and technical requirements.
Furthermore, a trunk is a Layer 2 point-to-point link between networking devices that can carry the traffic of multiple VLANs. ISL and 802.1Q are the two trunking protocols that connect two switches. The 802.1Q protocol is an open standard protocol also used for VLAN trunking.
VTP is used to distribute and synchronize information about VLANs configured throughout a switched network. VTP pruning helps to stop flooding of unnecessary traffic on trunk links. VTP configuration sometimes needs to be added to small network deployments, whereas VTP transparent mode is usually privileged for larger networks. When configuring VLANs over several switches, ensure that the configuration is compatible throughout switches in the same domain.
To increase bandwidth and provide redundancy, use EtherChannel by aggregating individual, similar links between switches. EtherChannel can be dynamically configured between switches using either the Cisco proprietary PAgP or the IEEE 802.3ad LACP. EtherChannel is configured by assigning interfaces to the EtherChannel bundle and configuring the resulting port channel interface. EtherChannel load balances traffic over all the links in the bundle. The method that is chosen directly impacts the efficiency of this load-balancing mechanism.