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Peng Hailin
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@ -66,20 +66,20 @@ Switch (config-if)#switchport trunk encapsulation dot1q
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此配置可通过命令 `show interfaces [name] switchport` 进行验证，如下列输出所示。
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<pre>
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```
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Switch#show interfaces FastEthernet1/1 switchport
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Name: Fa0/2
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Switchport: Enabled
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Administrative Mode: dynamic desirable
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Operational Mode: trunk
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<b>Administrative Trunking Encapsulation: dot1q</b>
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<b>Operational Trunking Encapsulation: dot1q</b>
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Administrative Trunking Encapsulation: dot1q
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Operational Trunking Encapsulation: dot1q
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Negotiation of Trunking: On
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Access Mode VLAN: 1 (default)
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Trunking Native Mode VLAN: 1 (default)
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...
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[Truncated Output]
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</pre>
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```
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中继端口配置的第三步，就是部署配置，以确保该端口已被指定为中继端口。可以通过两种方式完成。
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@ -119,19 +119,19 @@ Trunking Native Mode VLAN: 1 (default)
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尽管中继链路的静态配置强制交换机建立一条中继，动态 ISL 和动态中继协议（DTP）数据包仍能从该接口发出。这样做了后，一条静态配置的中继链路就可以与相邻的使用了 DTP 的交换机，建立起中继关系，接着的小节将会讲到。经由 `show interfaces [name] switchport` 命令的输出，便可验证这点。如下面的输出所示。
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<pre>
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```
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VTP-Server#show interfaces FastEthernet0/1 switchport
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Name: Fa0/1
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Switchport: Enabled
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Administrative Mode: trunk
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Operational Mode: trunkAdministrative Trunking Encapsulation: dot1q
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Operational Trunking Encapsulation: dot1q
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<b>Negotiation of Trunking: On</b>
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Negotiation of Trunking: On
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Access Mode VLAN: 1 (default)
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Trunking Native Mode VLAN: 1 (default)
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...
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[Truncated Output]
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</pre>
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```
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在上面的输出中，粗体文字表明尽管中继链路是静态配置的，端口仍然在发出 DTP 和 DISL 数据包。在一些场合，此特性被看成是不受欢迎的。因此，通过执行接口配置命令 `switchport nonegotiate`，在静态配置作为中继链路的端口上关闭 DISL 及 DTP 数据包发送，被认为是一种良好实践，具体操作如以下的输出。
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@ -147,20 +147,20 @@ VTP-Server(config)#
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再一次，`show interfaces [name] switchport` 命令可被用作验证配置，像下面这样。
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<pre>
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VTP-Server#<b>show interfaces FastEthernet0/1 switchport</b>
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```
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VTP-Server#show interfaces FastEthernet0/1 switchport
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Name: Fa0/1
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Switchport: Enabled
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Administrative Mode: trunk
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Operational Mode: trunk
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Administrative Trunking Encapsulation: dot1q
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Operational Trunking Encapsulation: dot1q
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<b>Negotiation of Trunking: Off</b>
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Negotiation of Trunking: Off
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Access Mode VLAN: 1 (default)
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Trunking Native Mode VLAN: 1 (default)
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...
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[Truncated Output]
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</pre>
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```
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### 动态中继协议，Dynamic Trunking Protocol, DTP
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@ -232,7 +232,7 @@ DTP information for FastEthernet0/1:
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默认情况下，802.1Q 中继将 VLAN 1 作为原生 VLAN。执行命令 `show interfaces [name] switchport` 或命令 `show interfaces trunk`，就可查看到默认原生 VLAN 是哪一个，如下面的输出所示。
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<pre>
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```
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VTP-Server#show interfaces FastEthernet0/1 switchport
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Name: Fa0/1
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Switchport: EnabledAdministrative Mode: trunk
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@ -241,11 +241,11 @@ Administrative Trunking Encapsulation: dot1q
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Operational Trunking Encapsulation: dot1q
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Negotiation of Trunking: On
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Access Mode VLAN: 1 (default)
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<b>Trunking Native Mode VLAN: 1 (default)</b>
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Trunking Native Mode VLAN: 1 (default)
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Voice VLAN: none
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...
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[Truncated Output]
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</pre>
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```
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交换机使用 VLAN 1 来承载一些特定的协议流量，比如思科发现协议（Cisco Discovery Protocol, CDP）、VLAN 中继协议（VLAN Trunking Protocol, VTP）、端口聚合协议（Port Aggregation Protocol, PAgP）, 以及动态中继协议（Dynamic Trunking Protocol, DTP） 等的协议信息。CDP 和 PAgP 将在今天的课程后面部分详细讨论。尽管默认原生 VLAN 总是 VLAN 1, 它是可以手动修改为任何不在**保留 VLANs** 中的任何有效 VLAN 编号的。
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@ -362,10 +362,10 @@ VTP-Server-1(config)#ip default-gateway 10.30.30.1
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图 3.4 中的路由器之配置如下面的输出所示。
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<pre>
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```
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R1(config)#interface FastEthernet0/0
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R1(config-if)#no ip address
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<b>R1(config-if)#no shut </b> <- 这一步相当重要，否则子接口也会处于 down down 状态
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R1(config-if)#no shut <- 这一步相当重要，否则子接口也会处于 down down 状态
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R1(config-if)#exit
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R1(config)#interface FastEthernet0/0.10
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R1(config-subitf)#description ‘Subinterface For VLAN 10’
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@ -382,7 +382,7 @@ R1(config-subitf)#description ‘Subinterface For Management’
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R1(config-subif)#encapsulation dot1Q 30 native
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R1(config-subif)#ip add 10.30.30.1 255.255.255.0
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R1(config-subif)#exit
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</pre>
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```
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此方案的主要优在于，路由器上仅需一个物理接口。主要的劣势在于，该物理端口的带宽，是为所配置的多个子接口所公用的。因此，如果存在很多 VLAN 间流量时，路由器就很快会成为网络的性能瓶颈。
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@ -496,7 +496,7 @@ Switch#
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要让交换机进行 VLAN 信息交换，这些交换机就务必要配置在同一个 VTP 域中，如下面的输出这样。
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<pre>
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```
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Switch(config)#vtp mode server ←this is on by default
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Switch(config)#vtp domain in60days
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Changing VTP domain name from NULL to in60days
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@ -506,8 +506,8 @@ Configuration Revision : 0
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Maximum VLANs Supported Locally : 255
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Number of Existing VLANs : 5
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VTP Operating Mode : Server
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VTP Domain Name : <b>in60days</b>
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</pre>
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VTP Domain Name : in60days
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```
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如要安全的传输 VTP 更新数据，可以为其加上一个口令，但要求 VTP 域中的每台交换机的口令都要匹配。
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@ -577,17 +577,17 @@ VLANs 是一种相当直观的交换机特性，它很少需要进行故障排
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- 接口务必要是 up/up
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- 中继链路两端的封装方式要匹配
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<pre>
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```
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SwitchA#show interface fa1/1 switchport
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Name: Fa1/1
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<b>Switchport: Enabled</b>
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<b>Administrative Mode: trunk</b>
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Switchport: Enabled
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Administrative Mode: trunk
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Operational Mode: trunk
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Administrative Trunking Encapsulation: dot1q
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Operational Trunking Encapsulation: dot1q
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Negotiation of Trunking: Disabled
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Access Mode VLAN: 0 ((Inactive))
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</pre>
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```
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+ VLAN 信息未有传输
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- 该 VLAN 在中继链路上阻塞了吗
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@ -627,15 +627,15 @@ VLAN 间路由故障可以多种形式出现，尤其是考虑在该过程中涉
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这里有个输出示例。
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<pre>
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```
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Cat-3550-1#show interfaces trunk
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Port Mode Encapsulation Status Native vlan
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Fa0/1 on <b>802.1q</b> trunking 1
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Fa0/2 on <b>802.1q</b> trunking 1
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Fa0/1 on 802.1q trunking 1
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Fa0/2 on 802.1q trunking 1
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Port Vlans allowed on trunk
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Fa0/1 1,10,20,30,40,50
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Fa0/2 1-99,201-4094
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</pre>
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```
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命令 `show interface trunk` 提供的另一重要细节是中继状态。从中继状态可以看出中继是否形成，同时在链路两端都要检查中继状态。如果接口未处于“中继”模式，那么接口的运行模式（on, auto, 等）是最重要的检查项，以弄清接口能否允许与链路另一端形成中继态（a trunking state）。
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@ -698,7 +698,7 @@ Fa0/2 1-99,201-4094
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1. 你需要在每台 PC 上添加 IP 地址。可自由选择，只要求它们在同一子网上。
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2. 在交换机 A 上设置主机名（hostname）, 创建 VLAN 2, 并将连接 PC 的那个接口放到 VLAN 2 中。如你愿意，你也可以赋予 VLAN 2 一个名称。
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<pre>
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```
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Switch>en
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Switch#conf t
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Enter configuration commands, one per line. End with CNTL/Z.
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@ -718,17 +718,17 @@ VLAN Name Status Ports
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Fa0/14, Fa0/15, Fa0/16, Fa0/17,
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Fa0/18, Fa0/19, Fa0/20, Fa0/21,
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Fa0/22, Fa0/23, Fa0/24
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<b>2 60days active Fa0/1</b>
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2 60days active Fa0/1
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1002 fddi-default active
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1003 token-ring-default active
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1004 fddinet-default active
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1005 trnet-default active
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SwitchA#
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</pre>
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```
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3. 将中继链路设置为中继模式。
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<pre>
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```
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SwitchA#conf t
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Enter configuration commands, one per line. End with CNTL/Z.
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SwitchA(config)#int FastEthernet0/2
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@ -737,12 +737,12 @@ SwitchA#show interface trunk
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Port Mode Encapsulation Status Native vlan
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Fa0/2 on 802.1q trunking 1
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Port Vlans allowed on trunk
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<b>Fa0/2 1-1005</b>
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</pre>
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Fa0/2 1-1005
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```
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4. 如你愿意，设置在该中继链路上仅允许 VLAN 2。
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<pre>
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```
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SwitchA(config)#int FastEthernet0/2
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SwitchA(config-if)#switchport trunk allowed vlan 2
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SwitchA(config-if)#^Z
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@ -752,8 +752,8 @@ SwitchA#show int trunk
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Port Mode Encapsulation Status Native vlan
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Fa0/2 on 802.1q trunking 1
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Port Vlans allowed on trunk
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<b>Fa0/2 2</b>
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</pre>
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Fa0/2 2
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```
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5. 此时，如你自其中一台 PC ping 往另一台，将会失败。这是因为一边是在 VLAN 1 中，另一边在 VLAN 2 中。
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