6509#conf t

    Enter configuration commands, one per line. End with CNTL/Z.

    6509（config）#interface gigabitEthernet 3/48 —进入级联接口

    6509（config-if）#switchport trunk ? —查看起Trunk后的情况

    allowed Set allowed VLAN characteristicswhen interface is in trunking modenative Set trunking

    native characteristics when interface is in trunking modepruning Set

    pruning VLAN characteristics when interface is in trunking mode

    VLAN无线上网交换机故障排除

    从上面可以看出：该端口不能强制进行IEEE 802.1Q的Trunk设置，其他接口情况都一样。此时想到超级引擎SUP720模块上还有一个接口没有用，看它能不能进行强制封帧。进入该端口的Trunk配置，看到如下信息。
 

 6509#conf t

    Enter configuration commands, one per line. End with CNTL/Z.

    6509（config）#interface gigabitEthernet 5/2

    6509（config-if）#switchport trunk ?

    allowed Set allowed VLAN characteristics when interface is in trunking mode

    encapsulation Set trunking encapsulation when interface is in trunking mode

    native Set trunking native characteristics when interface is in t runking mode

    pruning Set pruning VLAN characteristics when interface is in trunking mode

    下画线标示出的比在gigabitEthernet 3/48接口上看到的多了一个encapsulation选项，由此可见，在超级引擎模块的接口上可以强制进行IEEE 802.1Q的Trunk设置。