CCNP-30 DHCP 3(BSCI)

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 cc 00.0f 34.0000.

*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 cc 00.0f 34.0000.

*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 cc 00.0f 34.0000.

*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 cc 00.0f 34.0000.

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-cc 00.0f 34.0000-Fa0/0

   Client-ID hex dump: 636973636F 2D636330302E306633342E

                       303030302D 4661302F 30

   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。