Network monitoring is a base for network usage accounting, network auditing, intrusion detection, protocol analysis, flow statistics and other network-based application. Normally, network monitoring is quite common in low broadband networks, especially 100M/10M Ethernet. In high broadband backbones, for example Gigabit Ethernet and 2.5G POS (OC48) backbones, there are many problems, including tapping point, packet loss on NIC, packet loss on bus, processing performance and recording performance. The article considers the problem to be solved in broadband network monitoring, and describes a distributed network monitoring structure in broadband networks.