A content management system synchronizes content items across client computing systems connected by a network. Client devices connected to peer devices on a LAN utilize peer-to-peer synchronization to synchronize content items. Client devices on the LAN broadcast namespaces synchronized on the client devices with other devices on the LAN. Client devices on the LAN connect to a subset of client devices that share a namespace with the connecting client device based on the broadcasts. Upon receiving a notification from the content management system that a new content item has been synchronized with the namespace a client device sends requests for a block comprising a content item to a subset of the connected devices. Additional block requests are sent in the order of randomized blocklist.