ISL is a protocol that maintains VLAN information as traffic flows between the switches. With ISL, an Ethernet frame is encapsulated with a header that contains a VLAN ID.

• ISL是一个协定，它可以维护流经交换器之间传输的VLAN资讯。使用ISL时，乙太网路讯框会再度被封装，并配置一个具有VLAN识别码的标头。