CCNP-28 DHCP 1（BSCI）

CCNP-28 DHCP 1

实验拓扑：



试验要求：R1配置为DHCP SERVER，R2配置为DHCP CLIENT，使R2能够获得R1分配的IP与其他参数。
试验目的：掌握基本的CISCO
IOS DHCP SERVER与DHCP CLIENT配置。

实验配置：
R1：
DHCPSERVER(config)#service
dhcp //开启DHCP服务
DHCPSERVER(config)#ip
dhcp pool ccnp //定义DHCP地址池名字为ccnp
DHCPSERVER(dhcp-config)#network
199.99.1.0 255.255.255.0//定义dhcp分配地址范围为199.99.1.0/24网段的ip地址
DHCPSERVER(dhcp-config)#dns-server
202.102.224.68 202.102.240.65//定义DHCP
SERVER分配给CLIENT的DNS服务器地址，最少为一个，最多可以支持8个。
DHCPSERVER(dhcp-config)#default-router
199.99.1.1//定义默认网关
DHCPSERVER(dhcp-config)#exit
DHCPSERVER(config)#ip
dhcp excluded-address 199.99.1.200 199.99.1.254//定义DHCP SERVER在分配地址的时候199.99.1.200-199.99.1.254的地址不被分配出去
DHCPSERVER(config)#int f0/0
DHCPSERVER(config-if)#ip add 199.99.1.1
255.255.255.0
DHCPSERVER(config-if)#no shu
DHCPSERVER(config-if)#end

R2：
DHCPCLIENT(config)#int f0/0
DHCPCLIENT(config-if)#ip
address dhcp//使接口用DHCP方式获取IP
DHCPCLIENT(config-if)#no shu

配置完后，R2会提示：
*Mar
1 00:04:35.599: %DHCP-6-ADDRESS_ASSIGN: Interface FastEthernet0/0
assigned DHCP address 199.99.1.2, mask 255.255.255.0, hostname DHCPCLIENT
表示接口F0/0通过DHCP获得的IP地址是199.99.1.2/24。
下面我们在R2上show ip int br验证一下：
DHCPCLIENT#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.99.1.2 YES DHCP
up up
确实得到了这个ip地址。
我们再到R1上查看一下DHCP SERVER信息：
DHCPSERVER#show ip dhcp server statistics
Memory usage 23708
Address pools 1 //地址池数量1
Database agents 0
Automatic bindings 1//自动获得的数量1
Manual bindings 0
Expired bindings 0
Malformed messages 0
Secure arp entries 0

Message Received
BOOTREQUEST 0
DHCPDISCOVER 1//收到1个DHCPDISCOVER报文
DHCPREQUEST 1//收到1个DHCPREQUEST报文
DHCPDECLINE 0
DHCPRELEASE 0
DHCPINFORM 0

Message Sent
BOOTREPLY 0
DHCPOFFER 1//发送一个DHCPOFFER报文
DHCPACK 1// 发送一个DHCPACK报文
DHCPNAK 0
上面的输出完全符合DHCP分配IP地址的四次握手的规则：



下面我们分别在R1与R2上debug一下，观察一下DHCP的工作过程，首先在R1上debug ip dhcp
server packet,再在R2上debug dhcp，然后把R2的F0/0端口shut再no shut，观察调试信息：
DHCPSERVER#debug ip dhcp server packet
DHCPSERVER#
*Mar
1 00:10:34.103: DHCPD: DHCPRELEASE message received from client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 (199.99.1.3). //收到199.99.1.3释放IP地址的消息。
*Mar
1 00:10:36.079: DHCPD: DHCPRELEASE message received from client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 (199.99.1.3).
*Mar
1 00:10:36.083: DHCPD: Finding a relay for client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 on interface FastEthernet0/0.//在接口F0/0寻找中继。
*Mar
1 00:10:46.459: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 on interface
FastEthernet0/0. //在接口F0/0/收到0063.6973…..发来的DHCPDISCOVER消息。
*Mar
1 00:10:46.459: DHCPD: Allocate an address without class information
(199.99.1.0) //分配一个地址。
*Mar
1 00:10:48.459: DHCPD: Sending DHCPOFFER to client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 (199.99.1.4).//发送DHCPOFFER消息给客户端，包含分配给它的IP地址为199.99.1.4。
*Mar
1 00:10:48.459: DHCPD: broadcasting BOOTREPLY to client cc00.0978.0000.//广播BOOTREPLY给cc00.0978.0000客户。
*Mar
1 00:10:48.599: DHCPD: DHCPREQUEST received from client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30.//收到客户端发来的DHCPREQUEST报文。
*Mar
1 00:10:48.603: DHCPD: No default domain to append - abort update
*Mar
1 00:10:48.603: DHCPD: Sending DHCPACK to client 0063.6973.636f.2d63.6330.302e.3039.3738.2e30.3030.302d.4661.302f.30 (199.99.1.4).//发送DHCPACK给客户端用来确认。
*Mar
1 00:10:48.603: DHCPD: broadcasting BOOTREPLY to client cc00.0978.0000.

再到R2上查看一下调试信息：
DHCPCLIENT#debug dhcp
DHCP client activity debugging is on
DHCPCLIENT(config-if)#no shu
DHCPCLIENT#
*Mar
1 00:09:05.407: DHCP: DHCP client process started: 10//启动dhcp进程10
*Mar
1 00:09:05.423: RAC: Starting DHCP discover on FastEthernet0/0//在接口F0/0发送DHCP discover报文
*Mar
1 00:09:05.423: DHCP: Try 1 to acquire address for FastEthernet0/0//第一次尝试获取IP地址
*Mar
1 00:09:05.435: DHCP: allocate request//分配请求
*Mar
1 00:09:05.435: DHCP: zapping entry in DHC_PURGING state for Fa0/0
*Mar
1 00:09:05.435: DHCP: deleting entry 6407D740 199.99.1.3 from list
*Mar
1 00:09:05.439: DHCP: new entry. add to queue, interface FastEthernet0/0
*Mar
1 00:09:05.439: DHCP: SDiscover attempt # 1 for entry:// Discover报文的一些参数
*Mar
1 00:09:05.439: DHCP: SDiscover: sending 299 byte length DHCP packet
*Mar
1 00:09:05.439: DHCP: SDiscover 299 bytes
*Mar
1 00:09:05.443: B'cast on FastEthernet0/0 interface
from 0.0.0.0
*Mar
1 00:09:07.403: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state
to up
*Mar
1 00:09:07.751: DHCP: Received a BOOTREP pkt
*Mar
1 00:09:07.751: DHCP: offer received from 199.99.1.1//收到199.99.1.1的offer消息
*Mar
1 00:09:07.755: DHCP: SRequest attempt # 1 for entry:// Request报文的一些参数
*Mar
1 00:09:07.755: DHCP: SRequest- Server ID option: 199.99.1.1
*Mar
1 00:09:07.755: DHCP: SRequest- Requested IP addr option: 199.99.1.4
*Mar
1 00:09:07.755: DHCP: SRequest placed lease len option: 86400
*Mar
1 00:09:07.755: DHCP: SRequest: 317 bytes
*Mar
1 00:09:07.755: DHCP: SRequest: 317 bytes
*Mar
1 00:09:07.759: B'cast
on FastEthernet0/0 interface from 0.0.0.0
*Mar
1 00:09:07.903: DHCP: Received a BOOTREP pkt
*Mar
1 00:09:08.403: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/0, changed state to up
*Mar
1 00:09:11.919: DHCP Client Pooling: ***Allocated IP address: 199.99.1.4//获取199.99.1.4这个IP地址。
*Mar
1 00:09:11.995: Allocated IP address = 199.99.1.4 255.255.255.0//被分配的IP地址为199.99.1.4，掩码为255.255.255.0。
在R2上用show命令查看DHCP的一些信息：
DHCPCLIENT#show dhcp server

DHCP server: ANY (255.255.255.255)

Leases: 3

Offers: 3 Requests: 3 Acks : 3 Naks: 0

Declines: 0 Releases: 6 Query: 0 Bad: 0

DNS0: 202.102.224.68, DNS1:
202.102.240.65
Subnet:
255.255.255.0

DHCPCLIENT#show dhcp lease
Temp IP addr: 199.99.1.4 for peer on Interface: FastEthernet0/0
Temp
sub net mask: 255.255.255.0
DHCP
Lease server: 199.99.1.1, state: 3 Bound

DHCP transaction id: FC9

Lease: 86400 secs, Renewal: 43200
secs, Rebind: 75600 secs
Temp default-gateway addr: 199.99.1.1

Next timer fires after: 11:58:09

Retry count: 0 Client-ID:
cisco-cc00.0978.0000-Fa0/0

Client-ID hex dump: 636973636F2D636330302E303937382E
303030302D4661302F30

Hostname: DHCPCLIENT
DHCPCLIENT#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 199.99.1.1 to
network 0.0.0.0

C
199.99.1.0/24 is directly connected, FastEthernet0/0
S* 0.0.0.0/0
[254/0] via 199.99.1.1

从上面的输出可以看到DHCP分配给它的DNS和默认网关，还有DHCP SERVER的一些信息。

实验总结：掌握基本的DHCP SERVER与DHCP CLIENT的配置方法。

本文出自 “★Beckham~23” 博客，请务必保留此出处http://loveme23.blog.51cto.com/7891/51034