26.如下图，两个路由器(Atlanta 和 Brevard)用串口连接起来。但是他们之间没有数据传输，已知Atlanta配置正确，下图给出部分配置，路由器Brevard上导致该问题的原因是
A. A loopback is not set. A.没有设置loopback命令
B. The IP address is incorrect. B.IP地址不正确
C. The subnet mask is incorrect. C.子网掩码不正确
D. The serial line encapsulations are incompatible. D.串行链路封装不正确
E. The maximum transmission unit (MTU) size is too large.
E.最大传输单元(MTU)设置得太大
F. The bandwidth setting is incompatible with the connected interface.
F.带宽设置和直连的接口不匹配
Answer: B
27. Refer to the exhibit. Which switch provides the spanning-tree designated port role for the network segment that services the printers?
27.根据下图，哪个交换机为打印机提供了生成树中的指定端口角色?
A. Switch1 B. Switch2 C. Switch3 D. Switch4
Answer: C
