#ip dhcp pool global
(dhcp-config)#domain-name nhq.com
(dhcp-config)#network 192.168.1.0 255.255.255.0
(dhcp-config)#lease 7
ip dhcp pool global
network 192.168.1.0 255.255.255.0
domain-name nhq.com
default-router 192.168.1.254
lease 7
上面幾步做好就能使用DHCP Server了，但是這做的並不全面，比如做綁定，給網段分不同地址等都還沒做；我GNS3上面模擬的CISCO 3600路由器，沒找到Vlan的地址分配配置；
再貼一個DHCP Server服務的請求過程：
VPCS[1]> dhcp -d
Opcode: 1 (REQUEST)
Client IP Address: 0.0.0.0
Your IP Address: 0.0.0.0
Server IP Address: 0.0.0.0
Gateway IP Address: 0.0.0.0
Client MAC Address: 00:50:79:66:68:00
Option 53: Message Type = Discover
Option 12: Host Name = VPCS1
Option 61: Client Identifier = Hardware Type=Ethernet MAC Address = 00:50:79:66:
68:00
第一次請求，客戶端並沒有獲取到IP地址
Opcode: 2 (REPLY)
Client IP Address: 0.0.0.0
Your IP Address: 192.168.1.1
Server IP Address: 0.0.0.0
Gateway IP Address: 0.0.0.0
Client MAC Address: 00:50:79:66:68:00
Option 53: Message Type = Offer
Option 54: DHCP Server = 192.168.1.254
Option 51: Lease Time = 604394
Option 58: Renewal Time = 302197
Option 59: Rebinding Time = 528844
Option 1: Subnet Mask = 255.255.255.0
Option 15: Domain = nhq.com
Option 3: Router = 192.168.1.254
第一次答覆，DHCP服務器做的答覆，分配給客戶機一個192.168.1.1的地址，DHCP Server地址爲192.168.1.254
Opcode: 1 (REQUEST)
Client IP Address: 192.168.1.1
Your IP Address: 0.0.0.0
Server IP Address: 0.0.0.0
Gateway IP Address: 0.0.0.0
Client MAC Address: 00:50:79:66:68:00
Option 53: Message Type = Request
Option 54: DHCP Server = 192.168.1.254
Option 50: Requested IP Address = 192.168.1.1
Option 61: Client Identifier = Hardware Type=Ethernet MAC Address = 00:50:79:66:
68:00
Option 12: Host Name = VPCS1
客戶端第二次請求，已經獲取到IP地址
Opcode: 2 (REPLY)
Client IP Address: 192.168.1.1
Your IP Address: 192.168.1.1
Server IP Address: 0.0.0.0
Gateway IP Address: 0.0.0.0
Client MAC Address: 00:50:79:66:68:00
Option 53: Message Type = Ack
Option 54: DHCP Server = 192.168.1.254
Option 51: Lease Time = 604800
Option 58: Renewal Time = 302400
Option 59: Rebinding Time = 529200
Option 1: Subnet Mask = 255.255.255.0
Option 15: Domain = nhq.com
Option 3: Router = 192.168.1.254
IP 192.168.1.1/24 GW 192.168.1.254
DHCP服務器第二次答覆，確認IP地址已經被分配掉
這裏我們可以從Option 53這一行看到數據包的狀態，從Discover到Offer再到Request最後到Ack；
一次DHCP請求就這樣結束了