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-list 198 permit icmp 166.129.130.0 255.255.255.0 any
    access-list 198 deny icmp any any
    access-list 198 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 198 permit ip any any
C、access-list 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-list 100 permit icmp 166.129.130.0 0.0.0 255 any
    access-list 100 permit ip any any
    access-list 100 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{permit|deny}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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