DHCP和DHCP中继

 

 DHCP 和 DHCP 中继

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

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: DHCP DISCOVER 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 DHCP OFFER 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: DHCP REQUEST received from client 0063.6973.636f.2d30.3030.642e.3238.6631.2e30.3136.302d.4661.302f.30.

00:54:06.059: DHCPD: Sending DHCP ACK 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 BOOT REPLY 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