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: 636973636F 2D636330302E303937382E

                       303030302D 4661302F 30

   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