Cisco路由器执行show access-list命令显示如下一组信息 Standard IP access list block deny 10.0.0.0, wildcard bits 0.255.255.255 log deny 172.16.0

admin2015-07-23  25

问题 Cisco路由器执行show access-list命令显示如下一组信息
Standard IP access list block
deny 10.0.0.0, wildcard bits 0.255.255.255 log
deny 172.16.0.0, wildcard bits 0.15.255.255
permit any
根据上述信息,正确的access-list配置是(    )。

选项 A、Router (config) # access-list standard block
Router (config-std-nacl) # deny 10.0.0.0 255.0.0.0 log
Router (config-std-nacl) # deny 172.16.0.0 255.240.0.0
Router (config-std-nacl) # permit any
B、Router (config) # ip access-list standard block
Router (config-std-nacl) # permit any
Router (config-std-nacl) # deny 10.0.0.0 0.255.255.255 log
Router (config-std-nacl) # deny 172.16.0.0 0.15.255.255
C、Router (config) # ip access-list standard block
Router (config-std-nacl) # deny 10.0.0.0 255.0.0.0 log
Router (config-std-nacl) # deny 172.16.0.0 255.240.0.0
Router (config-std-nacl) # permit any
D、Router (config) # ip access-list standard block
Router (config-std-nacl) # deny 10.0.0.0 0.255.255.255 log
Router (config-std-nacl) # deny 172.16.0.0 0.15.255.255
Router (config-std-nacl) # permit any

答案D

解析 用名字标识访问控制列表的配置方法在全局配置模式下的命令格式为: ip access-list extended|standard access-list-number|name,在扩展或标准访问控制模式下配置过滤准则,命令格式为: permit|deny protocol source wildcard-mask destination wildcard-mask[operator][operand],根据以上命令格式首先排除A选项。B选项中permit放在deny前,这样deny命令不起作用,与题意不符。C项中应为子网掩码的反码,所以C错。因此,D选项正确。
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