在一台 Cisco路由器上执行 show access-lists命令显示如下一组信息 Extended IP access list port 4444 permit icmp 202.38.97.0,wildcard bits 0.0.0.255 an

admin2021-06-16  46

问题 在一台 Cisco路由器上执行 show access-lists命令显示如下一组信息
Extended IP access list port 4444
permit icmp 202.38.97.0,wildcard bits 0.0.0.255 any
deny icmp any any
deny udp any any eq 1434
deny tcp any any eq 4444
permit ip any any
根据上述信息,正确的access-list配置是(     )。

选项 A、Router(config)#ip access-list extended port4444
Router(config-ext-nacl)#deny icmp any any
Router(config-ext-nacl)#deny udp any any eq 1434
Router(config-ext-nacl)#deny tcp any any eq 4444
Router(config-ext -nacl)#permit icmp 202.38.97.0 0.0.0.255 any
Router(config-ext-nacl)#permit ip any any
B、Router(config)#access-list port4444 permit icmp 202.38.97.0 0.0.0.255 any
Router(config)#access-list port4444 deny icmp any any
Router(config)#access-list port4444 deny udp any any eq 1434
Router(config)#access-list port4444 deny tcp any any eq 4444
Router(config)#access-list port4444 permit ip any any
C、Router(config)#ip access-list extended port4444
Router(config-ext-nacl)#permit 202.38.97.0 0.0.0.255 any icmp
Router(config-ext-nacl)#deny any any icmp
Router(config-ext-nacl)#deny any any udp eq 1434
Router(config-ext-nacl)#deny any any tcp eq 4444
Router(config-ext-nacl)#permit ip any any
D、Router(config)#ip access-list extended port4444
Router(config-ext-nacl)#permit icmp 202.38.97.0 0.0.0.255 any
Router(config-ext-nacl)#deny icmp any any
Router(config-ext-nacl)#deny udp any any eq 1434
Router(config-ext-nacl)#deny tcp any any eq 4444
Router(config-ext-nacl)#permit ip any any

答案D

解析 从Extended IP access list port4444可以看出,访问列表采用了扩展配置模式,且访问列表名称为port44440命令为:ip access - list extended port44440从permit icmp202.38.97.0,wildcard bits 0.0.0.255  any可以看出,封禁ICMP协议,只允许202.38.97.0/24子网的ICMP报通过路由器。此外,其他的ICMP报全部禁止通过。命令为:permit icmp 202.38.97.0 0.0.0.255 any;deny icmp any anyo从deny udp any any eq 1434;deny tcp any any eq4444;permit ip any any可以看出,禁止了端口为1434的UDP数据包和端口为4444的TCP数据包。命令为:deny udp any any eq 1434;deny tcp any any eq 44440从permit ip any any可以看出,允许所有IP数据包通过路由器。命令为:permlt ip any any,故选择D选项。
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