选择题下列是一台Cisco路由器的部分路由表信息，表中的路由信息完全正确的是______。

A、 C 202.112.38.16 is directly connected, POS3/0 O E1 202.112.38.72[110/21]via 202.112.62.242, 2w6d, GigabitEthernet4/2 S 202.112.236.0/24[1/0]via 202.112.41.8 O E2 202.205.255.0/24[110/20]via 202.112.62.242, 7w0d, GigabitEthernet4/2 162.105.0.0/16 is variably subnetted, 209 subnets, 4 masks O 162.105.139.64/26[110/3]via 162.105.250.118, 10:35:25, GigabitEthernet7/0 B 168.160.0.0/16[200/70]via 202.112.63.254, 1w0d B 210.74.144.0/24[200/70]via 202.112.63.254, 1w0d S*0.0.0.0/0[1/0]via 202.112.38.17
B、 C 202.112.38.16 is directly connected, POS3/0 O E1 202.112.38.72[110/21]via 202.112.62.242, 2w6d, GigabitEthernet4/2 S 202.112.236.0/24[1/0]via 202.112.41.8 O E2 202.205.255.0/24[110/20]via 202.112.62.242, 7w0d, GigabitEthernet4/2 162.105.0.0/16 is variably subnetted, 209 subnets, 4 masks O 162.105.139.64/26[110/3]via 162.105.250.118, 10:35:25, GigabitEthernet7/0 B 168.160.0.0/16[200/70]via 202.112.63.254, 1w0d B 210.74.144.0/24[200/70]via 202.112.63.254, 1w0d S*0.0.0.0/24[1/0]via 202.112.38.17
C、 C 202.112.38.16 is directly connected, POS3/0 O E1 202.112.38.72[110/21]via 202.112.62.242, 2w6d, vlan62 S 202.112.236.0/24[1/0]via 202.112.41.8 O E2 202.205.255.0/24[110/20]via 202.112.62.242, 7w0d, vlan255 162.105.0.0/16 is variably subnetted, 209 subnets, 4 masks O 162.105.139.64/26[110/3]via 162.105.250.118, 10:35:25, vlan250 B 168.160.0.0/16[200/70]via 202.112.63.254, 1w0d B 210.74.144.0/24[200/70]via 202.112.63.254, 1w0d S*0.0.0.0/0[1/0]via 202.112.38.17
D、 C 202.112.38.16 is directly connected, POS3/0 O E1 202.112.38.72[110/21]via 202.112.62.242, 2w6d, GigabitEthernet4/2 S 202.112.236.0/24[1/0]via GigabitEthernet4/6 O E2 202.205.255.0/24[110/20]via 202.112.62.242, 7w0d, GigabitEthernet4/2 162.105.0.0/16 is variably subnetted, 209 subnets, 4 masks O 162.105.139.64/26[110/3]via 162.105.250.118, 10:35:25, GigabitEthernet7/0 B 168.160.0.0/16[200/70]via 202.112.63.254, 1w0d B 210.74.144.0/24[200/70]via 202.112.63.254, 1w0d S*0.0.0.0/0[1/0]via 202.112.38.17

【正确答案】 A

【答案解析】路由表中第一列指明路由源码，“C”表示为直连(connected)，管理距离0，表示目的网络直接与路由器的端口相连。“S”表示为静态(static)路由，管理距离1。“O”表示OSPF协议，管理距离110，E1表示OSPF外部路由类型1，E2表示OSPF外部路由类型2，*表示缺省路由(Candidate default)选项。选项B中“0.0.0.0/24[1/0]via 202.112.38.17”默认路由的子网掩码是0.0.0.0；选项C中“O E1 202.112.38.72[110/21]via 202.112.62.242,2w6d, vlan62”、“O E2 202.205.255.0/24[110/20]via 202.112.62.242, 7wod, vlan255”同一个地址“202.112.62.242”属于不同的虚拟子网“vlan62”和“vlan255”，同一个地址只能属于一个子网；选项D中“S 202.112.236.0/24[1/0]via GigabitEthernet4/6”via关键字后面填具体的IP地址。故选择A选项。