In 6G-enabled networks, fast and detailed network-wide monitoring is in urgent need for efficient resource allocation and intelligent network management. In-band Network Telemetry (INT) has been considered as a promising way for network monitoring by inserting the switch-internal states into probe packets. However, the packet size may exceed the Maximum Transmission Unit (MTU) due to querying on a per-switch basis on a long forwarding path. In addition, as an underlying primitive, the original INT framework does not support network-wide telemetry. Considering the limited packet size, several short forwarding paths with similar length should be generated to avoid the packet size exceeding MTU while achieving network-wide synchronous multipath telemetry. In this paper, we propose a novel INT framework named cluster based fast in-band network-wide telemetry (CFINT) to accomplish these tasks. Specifically, CFINT takes full advantage of the fact that the forwarding path from the cluster head to the cluster head is either 2-hop, 3-hop or 4-hop and utilizes minimum dominating set (MDS) to divide the network into several clusters. Based on the results of clustering, a series of short forwarding paths with similar length are generated in the way of intra-cluster and inter-cluster, respectively. Besides, CFINT specifies detailed packet encapsulation format, and further uses source routing to enable the probe packets to take through the forwarding paths on-demand. Extensive experimental results show that CFINT can overcome MTU limitation and significantly reduce the network-wide telemetry latency with an acceptable bandwidth overhead.