CCNP-29 DHCP 2(BSCI)
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CCNP-29 DHCP 2实验拓扑： 实验要求：R1配置为DHCP SERVER，R2配置为DHCP中继代理，R3配置为DHCP CLIENT。
试验目的：掌握路由器DHCP
helper-addresss的配置方法。
实验配置：
R1：
DHCPSERVER(config)#service
dhcp
DHCPSERVER(config)#ip
dhcp pool ccnp
DHCPSERVER(dhcp-config)#network
199.99.1.0 255.255.255.0
DHCPSERVER(dhcp-config)#default-router
199.99.1.1
DHCPSERVER(dhcp-config)#dns-server
199.99.1.253 199.99.1.254
DHCPSERVER(dhcp-config)#domain-name
cisco.com
DHCPSERVER(dhcp-config)#lease
2
DHCPSERVER(dhcp-config)#exit
DHCPSERVER(config)#ip
dhcp excluded-address 199.99.1.250 199.99.1.254
DHCPSERVER(config)#int f0/0
DHCPSERVER(config-if)#ip add
DHCPSERVER(config-if)#no shu
DHCPSERVER(config-if)#exit
DHCPSERVER(config)#ip route
DHCPSERVER(config)#end
R2：
DHCPRELAYAGENT(config)#int f0/0
DHCPRELAYAGENT(config-if)#ip add
DHCPRELAYAGENT(config-if)#no shu
DHCPRELAYAGENT(config-if)#exit
DHCPRELAYAGENT(config)#int f1/0
DHCPRELAYAGENT(config-if)#ip add 199.99.1.1
255.255.255.0
DHCPRELAYAGENT(config-if)#ip
helper-address
DHCPRELAYAGENT(config-if)#no shu
DHCPRELAYAGENT(config-if)#exit
DHCPRELAYAGENT(config)#ip
forward-protocol udp bootpc//允许bootpc（68）通过
DHCPRELAYAGENT(config)#ip
forward-protocol udp bootps//允许bootpc（67）通过
DHCPRELAYAGENT(config)#ip route
DHCPRELAYAGENT(config)#end
R3：
DHCPCLIENT(config)#int f0/0
DHCPCLIENT(config-if)#ip
add dhcp
DHCPCLIENT(config-if)#no shu
上面的是基本的配置，因为在接口设置完ip helper-address后，接口会转发所有的广播数据包，所以我们可以配置ip forward-protocol来控制转发广播包的类型，配置完成后我们看看R3的F0/0接口能不能获得正确的IP地址：
DHCPCLIENT#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.99.1.2 YES DHCP
up up
OK，得到了199.99.1.2这个IP地址，接下来我们在R2上开启debug ip dhcp server packet，然后再回到R3的F0/0接口，把它shut，再no shut，观察R2上出现的debug信息：
DHCPRELAYAGENT#debug ip dhcp server packet
DHCPRELAYAGENT#
*Mar
1 00:10:57.603: IP: s=
*Mar
1 00:10:57.607: DHCPD: setting giaddr to 199.99.1.1.
*Mar
1 00:10:57.607: IP: tableid=0, s=199.99.1.1 (local), d=
*Mar
1 00:10:57.607: IP: s=199.99.1.1 (local), d=
*Mar
1 00:10:57.611: DHCPD: BOOTREQUEST from 0063.
*Mar
1 00:10:57.831: IP: tableid=0, s=
*Mar
1 00:10:57.831: IP: s=
*Mar 1 00:10:57.835: IP: s=
*Mar
1 00:10:59.751: IP: tableid=0, s=
*Mar
1 00:10:59.751: IP: s=
*Mar
1 00:10:59.755: DHCPD: forwarding BOOTREPLY to client cc00.0d04.0000.
*Mar
1 00:10:59.755: DHCPD: broadcasting BOOTREPLY to client cc00.0d04.0000.
*Mar
1 00:10:59.759: IP: s=199.99.1.1 (local), d=255.255.255.255
(FastEthernet1/0), len 329, sending broad/multicast
*Mar
1 00:10:59.939: IP: s=
*Mar
1 00:10:59.943: DHCPD: Finding a relay for client 0063.
*Mar
1 00:10:59.943: DHCPD: setting giaddr to 199.99.1.1.//寻找到中继接口199.99.1.1（自己的理解）
*Mar
1 00:10:59.943: IP: tableid=0, s=199.99.1.1 (local), d=
*Mar
1 00:10:59.947: IP: s=199.99.1.1 (local), d=
*Mar
1 00:10:59.947: DHCPD: BOOTREQUEST from 0063.
*Mar
1 00:11:00.131: IP: tableid=0, s=
*Mar
1 00:11:00.131: IP: s=
*Mar
1 00:11:00.135: DHCPD: forwarding BOOTREPLY to client cc00.0d04.0000.//转发BOOTREPLY给cc00.0d04.0000。
*Mar
1 00:11:00.135: DHCPD: broadcasting BOOTREPLY to client cc00.0d04.0000.//广播BOOTREPLY给cc00.0d04.0000。
*Mar
1 00:11:00.139: IP: s=199.99.1.1 (local), d=255.255.255.255
(FastEthernet1/0), len 352, sending broad/multicast//向局域网内广播。
从上面的信息可以知道R2把R3发送来的广播包转变为单播数据包发送给R1，把R1发来的单播数据包转变为广播包在局域网内广播。
然后我们再到R3上查看一下：
DHCPCLIENT#show ip int br
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.99.1.3 YES DHCP
up up
得到了IP
199.99.1.3。
DHCPCLIENT#show dhcp server
DHCP server: ANY (255.255.255.255)
Leases: 2
Offers: 2 Requests: 2 Acks : 2 Naks: 0
Declines: 0 Releases: 3 Query: 0 Bad: 0
DNS0: 199.99.1.253, DNS1:
199.99.1.254
Subnet: 255.255.255.0 DNS
Domain: cisco.com
DHCPCLIENT#
*Mar
1 00:12:16.211:
-----Additional Debug------
*Mar
1 00:12:16.211: DHCP process ID 61 status 10
*Mar
1 00:12:16.211: DHCP Network Discovery is disabled
*Mar
1 00:12:16.211: DHCP NetDiscovery Informs 0 Discovers 0 Period 0
DHCPCLIENT#
DHCPCLIENT#show dhcp lease
Temp IP addr: 199.99.1.3 for peer on Interface: FastEthernet0/0
Temp
sub net mask: 255.255.255.0
DHCP Lease server:
DHCP transaction id:
Lease: 172800 secs, Renewal:
86400 secs, Rebind: 151200 secs
Temp default-gateway addr: 199.99.1.1
Next timer fires after: 23:58:03
Retry count: 0 Client-ID:
cisco-cc00.0d04.0000-Fa0/0
Client-ID hex dump:
303030302D
Hostname: DHCPCLIENT
也得到了DNS和DNS Domain的信息，租期为2天（172800 secs）。
DHCPCLIENT#show ip route
Codes: C - connected, S - static, R - RIP,
M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O -
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
C
199.99.1.0/24 is directly connected, FastEthernet0/0
S
S*
还得到了默认网关的信息，还有一条到DHCP SERVER的静态路由。
实验总结：掌握基本的路由器DHCP helper-address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/7891/51136 本文出自 51CTO.COM技术博客 |
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