PDF《Cisco DHCP部署》

18 2012 07:08 AM ? Displays the address conflicts that are found by a DHCP server ? IP Address: The IP address of the host as recorded on the DHCP server ? Detection Method: The manner in which the IP address of the hosts were found on the DHCP server;

can be a ping or a gratuitous ARP ? Detection time: The time when the conflict was found Ender ICND1 ― 4-42 The need for a centralized DHCP solution: ? Managing individual DHCP servers across many locations is time- consuming.管理处于不同VLAN或者地点的DHCP服务器耗费时间 ? Ensuring consistency in several different places can easily lead to errors.管理不同位置的服务器容易导致错误 To support a centralized DHCP solution in branch offices, only the DHCP relay agent needs to be configured. Ender ICND1 ― 4-43 Branch(config-if)# ip helper-address 172.16.1.100 ? Enables DHCP relay agent on a local interface ? DHCP中继代理的前提是路由相互可达,把不能通过跨越网段的广播封装到单播中实现 Ender ICND1 ― 4-44 Branch(config-if)# ip helper-address 172.16.1.100 Ender ICND1 ― 4-44 配置了Ip helper-address 会把UDP的报文都发给Server 全局下:ip forward-protocol {UDP [PORT]} 默认是转发所有的 UDP 数据 如果是只想转发dhcp的报文,那么需要 noip forward-protocol Ip forward-protocol udp

67 ip forward-protocol udp68 ? A DHCP server provides dynamic IP address assignment to end hosts, reducing errors and the time that is needed to administer address assignment. ? Before a client obtains an IP address from a DHCP server, it exchanges DHCP discover, offer, request, and acknowledge messages with the DHCP server. ? Both Cisco routers and Cisco Catalyst switches can be configured as DHCP servers. ? Use the verification commands show ip dhcp pool, show ip dhcp binding, and show ip dhcp conflict to monitor a DHCP server. ? When a centralized DHCP server is in use, configure DHCP relay agent functionally using the ip helper-address interface configuration command. Ender ICND1 ― 4-45 Thank you.