CIRcommitted information rate) 中文名:1 承诺信息速率 2 约定信息速率
     解释:在通常的情况下,按照协议应当达到信息传送速率,也就是说用户预先约定的数据速率.
     在EIGRP协议环境中,defalut是占用50%的接口带宽.我们应该知道.在frame relay 里面Cisco IOS软件认为点到点的帧中继子接口带宽为T1线路带宽(1.544Mbps),一个帧中继环境中CIR只有56K,EIGRP按默认占用50%的带宽来算,这样就会占用768Kbps,那么EIGRP就会吃掉很大的带宽.所以要在接口模式下使用bandwidth 单位是Kbps来给接口分配实际带宽,就是手工指定带宽!多点链路比如帧中继网络,把带宽配置成最小的CIR和VC之积 ,说白了,在点到点你把带宽和CIR设成一样的就OK!在多点和点到点混合网络,你先把点到点的连路设置了,因为点到点连路吃带宽较少.剩下的给多点SUB口平均分了就行了,在ISDN中方法,假如你的PVC是1M,那么你的CIR就设置PVC的一半就OK.

以下来自官方的文档

Pure Multipoint Configuration (No Subinterfaces)
In this configuration EIGRP will divide the configured bandwidth evenly across each virtual circuit. You must ensure that this will not overload each virtual circuit. For example, if you have a T1 access line with four 56K VCs, you should configure the bandwidth to be 224Kbps (4 * 56Kbps) in order to avoid dropping packets. If the total bandwidth of the virtual circuits equals or exceeds the access line speed, configure the bandwidth to equal the access line speed. Note that if the virtual circuits are of different capacities, the bandwidth must be set to take into account the lowest capacity virtual circuit.

For instance, if a T1 access line has three 256Kbps VCs and one 56Kbps VC, the bandwidth should be set to 224Kbps (4 * 56Kbps). In such configurations, putting at least the slow virtual circuit onto a point-to-point subinterface is strongly recommended (so that the bandwidth can be raised on the others).

Pure Point-to-Point Configuration (Each VC on a Separate Subinterface)
This configuration allows maximum bandwidth control, since the bandwidth can be configured separately on each subinterface, and is the best configuration if the virtual circuits have different capacities. Each subinterface bandwidth should be configured to be no greater than the available bandwidth on the associated VC, and the total bandwidth for all subinterfaces cannot exceed the available access line bandwidth. If the interface is oversubscribed, the access line bandwidth must be divided across each of the subinterfaces. For instance, if a T1 access line (1544 Kbps) has ten virtual circuits with a capacity of 256Kbps, the bandwidth on each subinterface should be configured to be 154Kbps (1544/10) instead of 256Kbps each.

Hybrid Configuration (Point-to-Point and Multipoint Subinterfaces)
Hybrid configurations should use combinations of the two individual strategies, while ensuring that the three basic rules are followed.

Examples
The examples in this section illustrate the relationship between topology and configuration. Only the configuration commands pertaining to EIGRP bandwidth usage are shown in these configuration examples.

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