Reducing the speed at which the scan is carried out (Throttling the scan speed) is the best approach when dealing with bandwidth limitations. It ensures that the vulnerability scan does not consume excessive bandwidth, which could slow down the network for legitimate users or cause disruptions. It also helps avoid triggering alarms that could alert network administrators to the scan's presence. Although performing the scan during off-peak hours or using less intrusive scan types may help, they do not directly address the problem of limited bandwidth as effectively as actively managing the scan's bandwidth usage.