High numbers on these counters may indicate low memory, an undersized CPU, or insufficient network bandwidth. Routers have finite resources, such as memory, CPU performance, and bandwidth, and insufficient amounts of any of these resources can lead to reduced performance. Fortunately, routers are continuously gathering statistics that provide clues. Administrators can use this information to determine whether they need to install a more powerful CPU, add more memory, or increase bandwidth. The flow chart on this page illustrates how a router receives packets and attempts to allocate resources to switch them.
Many steps occur during the processing of a packet, and tests are performed at each step.
The outcome of each step is recorded in an interface counter. Network administrators can analyze these interface counters to determine the reasons for sluggish router and network performance. The packet arrives on the interface and the router checks to see if its format is acceptable. Sometimes during transit, portions of a packet are lost. A high runt or giant count might indicate that a faulty device is delivering invalid traffic to a network segment.