单臂路由和DHCP实验

1、需求一：实施单臂路由实验（小型网络）通过在交换链路实施trunk和路由器的子接口功能，实现属于小型网络中，属于不同vlan的 两台PC的通信PC之间是通过两台交换机的e0/2 口来通信的，sw2的e0/3 口为BLK状态；（我没有修改到达e0/3的开销，故e0/2 口是根端口，可以接收和转发数据）1）那么首先，交换之间（2 口之间）配置trunk链路：先封装dotlq，再划到trunk上，但不划具体的vlan （这里不是配置本征vlan实验，不要配置允许通过哪些个vlan的流量）sw1到Branch之间也实施trunk，即交换机上一端封装dot1q，并划到trunk上，也不划vlan；路由器上

2、也封装dot1q，这一步是关键，路由器会通过dot1q封装来识别流量，配置的方式 和交换机上不同再分别将 sw1 和 sw2 的 1 口 access 到 vlan10 和 vlan202）然后，切记，PC1和PC2的网关的设置，如果不关闭PC的路由功能，那么pc1（路由器）到pc2 （路由器）是没有路由的（需要配置路由，可能是静态），数据包是不通的设置完毕后，需要测试网关是否可以ping通，这一步也是非常重要3）最后，测试PC1到PC2是否可以ping通1）sw1（config）#int e0/2sw1（config-if）#switchport trunk encapsulation do

3、t1qsw1（config-if）#switchport mode trunksw2（config）#int e0/2sw2（config-if）#switchport trunk encapsulation dot1qsw2（config-if）#switchport mode trunkBranch(config)#default int e0/0Interface Ethernet0/0 set to default configurationBranch(config)#do sh run int e0/0Building configuration.Current configura

4、tion : 44 bytes!interface Ethernet0/0no ip addressendBranch(config)#int e0/0.10Branch(config-subif)#encapsulation dotlQ 10Branch(config-subif)#ip address 10.1.10.254 255.255.255.0Branch(config-subif)#exiBranch(config)#int e0/0.20Branch(config-subif)#encapsulation dot1Q 20Branch(config-subif)#ip addr

5、ess 10.1.20.254 255.255.255.0 sw1(config)#int e0/1sw1(config-if)#switchport mode accesssw1(config-if)#switchport access vlan 10sw2(config)#int e0/1sw2(config-if)#switchport mode accesssw2(config-if)#switchport access vlan 20PC1(config)#int e0/1PC1(config-if)#ip address 10.1.10.100PC1(config-if)#ip a

6、ddress 10.1.10.100 255.255.255.0PC1(config-if)#exiPC1(config)#no ip routingPC1(config)#default gateway 10.1.10.254pc2(config)#default int e0/1Interface Ethernet0/1 set to default configuration pc2(config)#no ip routingpc2(config)#default gateway 10.1.20.254 pc2(config)#int e0/1pc2(config-if)#ip addr

7、ess 10.1.20.100 255.255.255.0 3)测试ping网关一开始ping2个网关均没ping通检查，pc1设置，没问题路由器设置也没问题最后发现，问题出在将sw1的e0/1划到trunk去了(应该划到vlan10的)，并且e0/0 口也 没有配置任何东西；清除这2个端口上的所有配置，重新操作后，发现可以ping通了sw1(config)#default int e0/1Interface Ethernet0/1 set to default configuration*Mar 7 09:25:03.528: %LINK-3-UPDOWN: Interface Ethern

8、et0/1, changed state to up*Mar 7 09:25:04.529: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1, changed state to upsw1(config)#int e0/1sw1(config-if)#switchport mode accesssw1(config-if)#switchport access vlan 10sw1(config-if)#exisw1(config)#default int e0/0Interface Ethernet0/0 set to d

9、efault configuration*Mar 7 09:26:27.190: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet。/。, changed state to down*Mar 7 09:26:30.194: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up sw1(config)#int e0/0sw1(config-if)#switchport trunk encapsulation dot1qsw1(

10、config-if)#switchport mode trunkPC1#ping 10.1.20.254Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.1.20.254, timeout is 2 seconds:.!Success rate is 20 percent (1/5), round-trip min/avg/max = 5023/5023/5023 msPC1#ping 10.1.10.254Type escape sequence to abort.Sending 5, 100-byte IC

11、MP Echos to 10.1.10.254, timeout is 2 seconds:!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms这里我有疑问，求解析：pc1 为什么可以 ping 通 10.1.20.254pc1上的arp表象中为什么不会有10.1.20.254需求二：在小型网络里实施DHCPBranch作为DHCP服务器，并为PC1和PC2都分配ip在小型网络中，配置静态IP地址，有很多缺点，比如可能会出现地址冲突(两台设备配置 了同一个ip)；工作量很大并且没有扩展性可言；于是，在网络中需

12、要动态主机控制协议(DHCP)，它可以根据用户的vlan属性，分配ip地址1)首先，cisco设备中DHCP是默认开启的，关闭是Branch(config)#no service dhcpBranch(config)#ip dhcp pool yanghaibo配置 vlan10 的地址池Branch(dhcp-config)#network 10.1.10.0 /24/配置子网Branch(dhcp-config)#default-router 10.1.10.254/配置默认网关Branch(dhcp-config)#dns-server 114.114.114.114/配置 DNS 服务

13、器Branch(dhcp-config)#lease 1 16/配置租用日期Branch(dhcp-config)#exiBranch(config)#ip dhcp excluded-address 10.1.10.101 10.1.10.254/排除一些地址Pc1上这样配置PC1#conftEnter configuration commands, one per line. End with CNTL/Z.PC1(config)#int e0/1PC1(config-if)#ip address dhcpPC1(config-if)#在 Branch 上敲了 debug DHCP det

14、ail，结果在 pc1 上有调试信息，由于(PC1(config-if)#ip address dhcp)敲了 2次，pc1被自动分配了 2次地址：*Mar 7 10:11:46.172: %DHCP-6-ADDRESS_ASSIGN: Interface Ethernet0/1 assigned DHCPaddress 10.1.10.1, mask 255.255.255.0, hostname PC1PC1(config-if)#ip address dhcpPC1(config-if)#*Mar 7 10:12:08.463: %DHCP-6-ADDRESS_ASSIGN: Inter

15、face Ethernet0/1 assigned DHCPaddress 10.1.10.2, mask 255.255.255.0, hostname PC1上面是vlan1的地址池Branch(config)#ip dhcp pool yanghaibo 2Branch(dhcp-config)#network 10.1.20.0 /24Branch(dhcp-config)#default-router 10.1.20.254Branch(dhcp-config)#dns-server 114.114.114.114Branch(dhcp-config)#lease 1 16Branc

16、h(dhcp-config)#exiBranch(config)#ip dhcp excluded-address 10.1.20.101 10.1.20.254 pc2enpc2#conf tEnter configuration commands, one per line. End with CNTL/Z.pc2(config)#int e0/1pc2(config-if)#ip address dhcppc2(config-if)#*Mar 7 10:18:18.537: %DHCP-6-ADDRESS_ASSIGN: Interface Ethernet0/1 assigned DH

17、CP address 10.1.20.1, mask 255.255.255.0, hostname pc2在pc2上开启debug dhcp再次敲自动分配地址的命令，得到如下调试信息：pc2#debug dhcpDHCP client activity debugging is on pc2(config-if)#ip address dhcp*Mar 7 10:20:31.942: DHCP: Sending notification of TERMINATION:*Mar 7 10:20:31.942: Address 10.1.20.1 mask 255.255.255.0*Mar 7

18、 10:20:31.942: DHCP: Client socket is opened*Mar 7 10:20:31.942: DHCP: SRelease attempt # 1 for entry:*Mar 7 10:20:31.942: DHCP: SRelease placed Server ID option: 10.1.20.254*Mar 7 10:20:31.942: DHCP: SRelease: 279 bytes*Mar 7 10:20:33.108: DHCP: SRelease attempt # 2 for entry:*Mar 7 10:20:33.108: D

19、HCP: SRelease placed Server ID option: 10.1.20.254*Mar 7 10:20:33.108: DHCP: SRelease: 279 bytes*Mar 7 10:20:35.129: DHCP: SRelease attempt # 3 for entry:*Mar 7 10:20:35.129: DHCP: SRelease placed Server ID option: 10.1.20.254*Mar 7 10:20:35.129: DHCP: SRelease: 279 bytes pc2(config-if)#*Mar 7 10:20

20、:37.489: RAC: DHCP stopped on interface Ethernet0/1*Mar 7 10:20:37.489: DHCP: DHCP client process started: 10*Mar 7 10:20:37.494: RAC: Starting DHCP discover on Ethernet0/1*Mar 7 10:20:37.494: DHCP: Try 1 to acquire address for Ethernet0/1*Mar 7 10:20:37.507: DHCP: allocate request*Mar 7 10:20:37.50

21、7: DHCP: zapping entry in DHC_PURGING state for Et0/1*Mar 7 10:20:37.507: DHCP: deleting entry B4406420 10.1.20.1 from list*Mar 7 10:20:37.507: DHCP: new entry. add to queue, interface Ethernet0/1*Mar 7 10:20:37.507: DHCP: SDiscover attempt # 1 for entry:*Mar 7 10:20:37.507: DHCP: SDiscover: sending

22、 292 byte length DHCP packet pc2(config-if)#*Mar 7 10:20:37.507: DHCP: SDiscover 292 bytes*Mar 7 10:20:37.507:Bcast on Ethernet0/1 interface from 0.0.0.0pc2(config-if)#*Mar 7 10:20:39.538: DHCP: Received a BOOTREP pkt*Mar 7 10:20:39.538: DHCP: offer received from 10.1.20.254*Mar 7 10:20:39.538: DHCP: SRequest attempt # 1 for entry:*Mar 7 10:20:39.538: DHCP: