A.配置不当，防火墙会引起严重问题
B.很多应用不能安全通过防火墙
C.用户可能会积极寻找绕过防火期接收被阻信息的方法，使网络遭受潜在攻击的危险
D.未授权的流量可能经隧道或隐藏在合法的流量中通过防火墙

A.SMTP
B.Telnet
C.FTP
D.DNS

A.The command is accepted and the respective VLAN is added to vlan dat.
B.The command is rejected.
C.The command is accepted and you must configure the VLAN manually.
D.The port turns amber.

A.防止敏感用户和应用暴露于不受信任的用户前
B.网络性能提升
C.净化协议流量，防止暴露协议漏洞
D.正确的配置防火墙后，使得安全策略的实现更简单、可扩展、更健壮

A.RIP is an example of distance vector routing protocols.
B.Updates are periodic and include the entire routing table.
C.Routing updates are sent only after topology changes
D.The protocol can be useful in hub-and-spoke and hierarchical networks.
E.Convergence is usually faster than with link state protocols
F.Each router has its own view of the topology

A.10.10.0.0/18 subnetted with mask 255.255.255.252
B.10.10.0.0/25 subnetted with mask 255.255.255.252
C.10.10.0.0/24 subnetted with mask 255.255.255.252
D.10.10.0.0/23 subnetted with mask 255.255.255.252
E.10.10.0.0/16 subnetted with mask 255.255.255.252

A.ICMP消息
B.Traceroute
C.DOS TCP SYN
D.DOS smurf

A.Addresses are allocated after a negotiation between the server and the host to determine the length ofthe agreement.
B.Addresses are assigned for a fixed period of time.At the end of period，a newquest for an address mustbe made ，and another address is then assigned.
C.Addresses are leased to host.A host will usually keep the same address by periodicallycontacting theDHCP sever to renew the lease.
D.Addresses are permanently assigned so that the host uses the same address at all times.

A.spanning-tree backbonefast
B.spanning-tree uplinkfast
C.spanning-tree portfast
D.spanning-tree cost512

A.拒绝服务器攻击
B.IP地址欺骗
C.DOS TCP SYN攻击
D.DOS smurf攻击