定义一个用于封禁ICMP协议而只允许转发166.129.130.0/24子网的ICMP数据包的访问控制列表,Cisco路由器的正确配置是( )。

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问题 定义一个用于封禁ICMP协议而只允许转发166.129.130.0/24子网的ICMP数据包的访问控制列表,Cisco路由器的正确配置是(    )。

选项 A、access.1ist 198 permit icmp 166.129.130.0 255.255.255.0 any
    access—list 198 deny icmp any any
access—list 1 98 permit ip any any
B、access—list 198 permit icmp 166.129.130.0 0.0.0 255 any
    access—list 198 deny icmp any any
access—list 1 98 permit ip any any
C、access—1ist 99 permit icmp 166.129.130.0 0.0.0 255 any
    access—list 99 deny icmp any any
access—list 99 permit ip any any
D、access—1ist 100 permit icmp 166.129.130.0 0.0.0 255 any
    access—1ist 1 00 permit ip any any
    access—list 1 00 deny icmp any any

答案B

解析 封禁ICMP协议属于配置扩展访问控制列表,所以表号范围为100~199或2000~2699,格式为:access-list access-list-number{permitldeny)protocol source wildcard-mask destination wildcard.mask[operator][operand]。因为wildcard-mask为子网掩码的反码,所以根据以上描述,本题选项B)正确。
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