Each machine in a cluster of Yioop instances with the same Name Server has a channel, defaulting to 0. The Server Channel drop down is populated with a list of channels of currently configured machines in the cluster. If there are no configured machines and empty message is displayed. The Server Channel of a crawl is used to specify which machines in the cluster will participate in the crawl -- only machine with the same channel as that of the crawl will participate. Using this mechanism it is possible to set up several ongoing simultaneous crawls provided they are on different channels.