CCNP-30 DHCP 3

实验拓扑：

实验要求：把R1配置为DHCP SERVER，把SW配置为DHCP RELAY AGENT，把R2配置为DHCP CLIENT。
试验目的：掌握交换机DHCP中继代理的配置方法。

试验配置：
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)#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 199.99.1.250 255.255.255.0
DHCPSERVER(config-if)#no shu
DHCPSERVER(config-if)#exit

 

SW：
SW(config)#service dhcp //开启交换机的DHCP服务

SW(config)#ip dhcp relay information option //开启DHCP中继代理option82选项

SW(config)#exit
SW#vlan database
SW(vlan)#vlan 10
SW(vlan)#exit
SW#config t
SW(config)#int range f0/0 - 15
SW(config-if-range)#switchport access vlan 10
SW(config-if-range)#exit
SW(config)#int vlan 10
SW(config-if)#ip add 199.99.1.1 255.255.255.0
SW(config-if)#ip helper-address 199.99.1.250

SW(config-if)#ip dhcp relay information trusted //配置DHCP中继代理信任选项

SW(config-if)#exit

 

R2：
DHCPCLIENT(config)#int f0/0
DHCPCLIENT(config-if)#ip add dhcp

DHCPCLIENT(config-if)#no shu
按照上面的配置完成后，在R2上show ip int br查看一下接口是否得到了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     
好的，正确得到了IP地址，下面我们在SW上开启debug ip dhcp server packet，再到R2把F0/0接口shut再no shut一下，观察SW上的调试信息：
SW#debug ip dhcp server packet
SW#             
*Mar  1 00:10:56.575: DHCPD: setting giaddr to 199.99.1.1.
*Mar  1 00:10:56.579: DHCPD: adding relay information option.//加入option82选项

*Mar  1 00:10:56.579: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6330.302e.3066.3334.2e30.3030.302d.4661.302f.30 forwarded to 199.99.1.250.
*Mar  1 00:10:58.675: DHCPD: forwarding BOOTREPLY to client cc00.0f34.0000.
*Mar  1 00:10:58.675: DHCPD: validating relay information option.//通过option82选项

*Mar  1 00:10:58.675: DHCPD: broadcasting BOOTREPLY to client cc00.0f34.0000.
*Mar  1 00:10:58.679: DHCPD: Finding a relay for client 0063.6973.636f.2d63.6330.302e.3066.3334.2e30.3030.302d.4661.302f.30 on interface Vlan10.
*Mar  1 00:10:58.679: DHCPD: setting giaddr to 199.99.1.1.
*Mar  1 00:10:58.679: DHCPD: adding relay information option. //加入option82选项

*Mar  1 00:10:58.683: DHCPD: BOOTREQUEST from 0063.6973.636f.2d63.6330.302e.3066.3334.2e30.3030.302d.4661.302f.30 forwarded to 199.99.1.250.
*Mar  1 00:10:58.995: DHCPD: forwarding BOOTREPLY to client cc00.0f34.0000.
*Mar  1 00:10:58.995: DHCPD: validating relay information option. //通过option82选项

*Mar  1 00:10:58.995: DHCPD: broadcasting BOOTREPLY to client cc00.0f34.0000.
上面用红颜色标记的部分就是有关中继代理option82选项的信息，option82选项是用来验证DHCP信息的准确性的，有关option82选项的详细信息，请参照RFC3046。然后在SW上show ip dhcp relay information trusted-sources：

SW#show ip dhcp relay information trusted-sources
List of trusted sources of relay agent information option:
Vlan10

 

然后我们再回到R2上察看几个show命令：
DHCPCLIENT#show ip int br
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            199.99.1.3      YES DHCP   up                    up     

 

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: 199.99.1.250, state: 3 Bound
   DHCP transaction id: 186E
   Lease: 86400 secs,  Renewal: 43200 secs,  Rebind: 75600 secs
Temp default-gateway addr: 199.99.1.1
   Next timer fires after: 11:59:34
   Retry count: 0   Client-ID: cisco-cc00.0f34.0000-Fa0/0
   Client-ID hex dump: 636973636F2D636330302E306633342E
                       303030302D4661302F30
   Hostname: DHCPCLIENT

 

DHCPCLIENT#show dhcp server
   DHCP server: ANY (255.255.255.255)
    Leases:   2
    Offers:   5      Requests: 2     Acks : 4     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#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
得到了所有DHCP SERVER分配给它的信息，在R1上show ip dhcp binding：
DHCPSERVER#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address          Client-ID/              Lease expiration        Type
                    Hardware address/
                    User name
199.99.1.3          0063.6973.636f.2d63.    Mar 02 2002 12:11 AM    Automatic
                    6330.302e.3066.3334.

                    2e30.3030.302d.4661.

                    302f.30

注意用红颜色标记的部分并不是R2的F0/0接口的MAC地址，它是Client-ID，用来识别某个接口的。

实验总结：掌握基本的交换机DHCP中继代理的配置方法。