DHCP和DHCP中继实验及研究
1.1组网需求
随着网络的扩大，网络的信息点不断增加，手动配置和维护IP地址带来大量的管理和维护的负担，并且经常出现地址冲突，为了减轻网络的维护负担则出现了一种新的技术——DHCP
1.2组网拓扑
1.3实验目标
①熟悉层次化配制方法
②实现局域网内需要自动获取地址的PC能通过DHCP服务器获取IP 和DNS
③分析PC从DHCP服务器获取IP地址的过程
④分析PC通过中继设备从服务器获取IP地址的过程 www.it165.net
⑤了解为什么使用排除地址
⑥了解dhcp各种报文的格式
1.4实验步骤
14.1 基本配置
R7(config)#no ip domain-lookup
R7(config)#line console 0
R7(config-line)# logging synchronous
R7(config-line)# exec-timeout 0 0
R7(config-line)# no login
R7(config-line)#
R7(config-line)#line vty 0 4
R7(config-line)# no login
1.4.2二层链路及vlan配置和调试
1.4.3三层接口配置和调试
将R7做成单臂路由
R7(config-subif)#int f0/0.10
R7(config-subif)#en do 10
R7(config-subif)#ip add 192.168.10.1 255.255.255.0
R7(dhcp-config)#default-router 192.168.10.1
R7(dhcp-config)#dns-server 59.51.78.211
R7(config)#ip dhcp excluded-address 192.168.10.1
R7(config-subif)#int f0/0.20
R7(config-subif)#en do 20
R7(config-subif)#ip add 192.168.20.1 255.255.255.0
R7(config-subif)#no shut
R7(dhcp-config)#default-router 192.168.20.1
R7(dhcp-config)#dns-server 59.51.78.211
R7(config)#ip dhcp excluded-address 192.168.20.1
1.4.5 DHCP客户端
使用路由器模拟PC机作为dhcp客户端
R6(config)#int f0/0
R6(config-if)#ip add dhcp
R6(config-if)#no shut
R6(config-if)#exit
R6(config)#no ip routing
Router(config)#int e 0
Router(config-if)#ip add dhcp
Router(config-if)#no shut
Router(config-if)#exit
Router(config)#no ip routing
R7#debug ip dhcpserver packet
00:54:04.055: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 on interface FastEthernet0/0.10.
00:54:06.055: DHCPD: Sending DHCPOFFER to client
0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 (192.168.10.2).
0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 (192.168.10.2).
00:54:06.055: DHCPD: broadcasting BOOTREPLY to client 000d.28f1.0160.
00:54:06.059: DHCPD: DHCPREQUEST received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30.
00:54:06.059: DHCPD: Sending DHCPACK to client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 (192.168.10.2).
00:54:06.059: DHCPD: broadcasting BOOTREPLY to client 000d.28f1.0160.
1.4.6全网连通性测试
R6#ping 192.168.20.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.20.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 4/4/4 ms
r8#ping 192.168.10.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms
在配置完成之后没有debug信息后来发现没有在sw13上划分vlan 划过之后 r6不能自动获取ip地址 show ip int b 后发现
R6#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES manual up up
FastEthernet0/1 unassigned YES unset administratively down down
Serial1/0 unassigned YES unset administratively down down
Serial1/1 unassigned YES unset administratively down down
Serial1/2 unassigned YES unset administratively down down
Manual 为手动 所以要为r6配置dhcp 配置后成功获取ip地址
1.5DHCP中继
拓扑图
Dhcp中继是当dhcp服务器与dhcp客户端不在同一广播域时，需要使用dhcp中继技术让中间的三层设备为其中继转发dhcp报文
清楚之前的实验dhcp配置
R7(config)#no ip dhcp pool vlan10
R7(config)#no ip dhcp pool vlan20
R7(config)#no ip dhcp excluded-address 192.168.10.1
R7(config)#no ip dhcp excluded-address 192.168.20.1
三层接口配置和调试
R4(config)#int e0/1
R4(config-if)#ip add 192.168.1.1 255.255.255.0
R4(config-if)#no shut
R4(config-if)#end
R7(config)#int f0/1
R7(config-if)#ip add 192.168.1.2 255.255.255.0
R7(config-if)#no shut
R7(config-if)#end
R4#ping 192.168.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 1/2/4 ms
R7#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES unset up up
FastEthernet0/0.10 192.168.10.1 YES manual up up
FastEthernet0/0.11 unassigned YES manual deleted down
FastEthernet0/0.20 192.168.20.1 YES manual up up
FastEthernet0/0.21 unassigned YES manual deleted down
FastEthernet0/1 192.168.1.2 YES manual up up
Dhcp服务器配置
R4(config)#ip dhcp pool vlan10
R4(dhcp-config)#network 192.168.10.0 255.255.255.0
R4(dhcp-config)#default-router 192.168.10.1
R4(dhcp-config)#dns-server 59.51.78.211
R4(dhcp-config)#exit
R4(config)#ip dhcp excluded-address 192.168.10.1
R4(config)#ip route 192.168.10.0 255.255.255.0 192.168.1.2
R4#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
S 192.168.10.0/24 [1/0] via 192.168.1.2
C 192.168.1.0/24 is directly connected, Ethernet0/1
R4#ping 192.168.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
中继设备配置
R7(config)#int f0/0.10
R7(config-subif)#ip helper-add
R7(config-subif)#ip helper-address 192.168.1.1
R7(config-subif)#end
Pc机dhcp获取ip地址
6(config)#int f0/0
R6(config-if)#ip add dhcp
R6(config-if)#no shut
03:20:21.075: %DHCP-6-ADDRESS_ASSIGN: Interface FastEthernet0/0 assigned DHCP address 192.168.10.2, mask 255.255.255.0, host
R6#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.10.2 YES uP up up
R4#debug ip dhcp server packet
R4#
03:27:01.345: DHCPD: DHCPRELEASE message received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30
03:27:01.345: DHCPD: 192.168.10.1 is not a local address.
03:27:01.405: DHCPD: DHCPRELEASE message received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30
03:27:01.405: DHCPD: 192.168.10.1 is not a local address.
03:27:02.343: DHCPD: DHCPRELEASE message received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30
03:27:02.343: DHCPD: 192.168.10.1 is not a local address.
03:27:03.421: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 through relay 192.168.10.1.
03:27:05.424: DHCPD: Sending DHCPOFFER to client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 (192.168.10.2).
03:27:05.424: DHCPD: unicasting BOOTREPLY for client 000d.28f1.0160 to relay 192.168.10.1.//单路广播
03:27:05.436: DHCPD: DHCPREQUEST received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30.
03:27:05.436: DHCPD: Sending DHCPACK to client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30 (192.168.10.2).
03:27:05.436: DHCPD: unicasting BOOTREPLY for client 000d.28f1.0160 to relay 192.168.10.1.//单路广播
R4# undebug all
All possible debugging has been turned off
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