In Data Center Network (DCN), multiple tenants may interfere with each other, which leads to unpredictable application performance. Reserving bandwidth resources can hardly guarantee high network utilization, which may result in revenue loss of cloud providers. To address above problems, a Minimum Access Guaranteed Bandwidth Allocation (MAGBA) mechanism for data center networks was proposed. To provide the minimum bandwidth guarantee and make full use of idle bandwidth for tenants, the MAGBA scheduled traffic of Virtual Machine (VM) through Weighted Fairness Queuing at the sending side, and it adjusted TCP flow's receiving window at the receiving side. Through simulations on NS2 (Network Simulation version 2) platform, compared with the static resource reservation method, MAGBA mechanism was more flexible in bandwidth allocation and it could improve the network throughput by 25%. When some tenants sent a lot of TCP flows, the other tenants in the MAGBA obtained higher bandwidth than that in the existing bandwidth allocation mechanism based on TCP flows. The simulation results show that the MAGBA mechanism can provide minimum access guaranteed bandwidth for VMs and it can avoid interferences from other tenants.