1、Cisco路由器的Trunk 与子接口的讨论First, look at the subinterface numbers. The subinterface number begins with the period,like .10 and .20 in this case. These numbers can be any number from 1 up through a very large number (over 4 billion). The number just needs to be unique among all subinterfaces associated w
2、ith this one physical interface. In fact, the subinterface number does not even have to match the associated VLAN ID. (The encapsulation command, and not the subinterfacenumber, defines the VLAN ID associated with the subinterface.)（案：也就是说路由器子接口的 number 与 encapsulation dot1Q 后面的 number 可以不一致，接收特定 VL
3、AN 的帧时，起作用的是 encapsulation dot1Q 后面的 number 如：encapsulation dot1Q：启用路由器的 802.1Q 封装，此 e0/0.111 只接收 vlan 10 的数据帧。 ）Each 802.1Q trunk has one native VLAN ，and when used,the configuration to use that native VLAN differs,with two options for the router side of configuration:Router side:1、 Configure the i
4、p address command on the physical interface ,but without an encapsulation command;the router considers this physical interface to be using the native VLAN.（案：交换机一端是 native VLAN 是 1 ，路由器一端为：也可以是：）2、 Configure the ip address command on a subinterface,and use the encapsulation .native subcommand.（如果不指定
5、 dot1Q 的封装，那么子接口 IP 无法配到子接口下面。）最后需要注意：NOTE Although not required, most sites do choose to make the subinterface numbermatch the VLAN ID !Each subinterface configuration lists two subcommands. One command (encapsulation) enables trunking and defines the VLAN whose frames are considered to be coming i
6、n and out of the subinterface. The ip address command works the same way it does on any other interface. Note that if the physical Ethernet interface reaches an up/up state, the subinterface should as well, Each subinterface configuration lists two subcommands. One command (encapsulation) enables tr
7、unking and defines the VLAN whose frames are considered to be coming in and out of the subinterface. The ip address command works the same way it does on any other interface. Note that if the physical Ethernet interface reaches an up/up state, the subinterface should as well,提问：Router 端的 native VLAN
8、与Switch端的native VLAN不一致，Trunk是否起的来？通过gns3的实验，Trunk链路可以启用，正常使用！也就是说：Router：Switch：Router与 Swtich可以 ping通！在Router 上可以用 show vlans查看相关：结论：the show vlans command on a router spells out which router trunk interfaces use which VLANs, which VLAN is the native VLAN, plus some packet statistics.修改路由器子接口的本征VLAN用意何在？The Layer 2 switch function forwards frames inside each VLAN, but it will not forward frames between VLANs. The Layer 3 forwarding logicroutingforwards IP packets between VLANs.
