在AireOS的環境下，如果我們想讓一個WLAN對應多個VLAN，通常來說，大家的選擇可能是通過interface Group的方式來實現WLAN和多個VLAN的對應。而在C9800的環境下，不再是接口和WLAN綁定的概念，在C9800上，是在Policy Profile中配置需要的VLAN。
但是，在使用VLAN Group，需要注意相關的限制，尤其是在FlexConnect的使用場景！如下是相關限制。
Restrictions for VLAN Groups
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If the number of VLANs in a VLAN group exceeds 32, the mobility functionality might not work as expected and Layer 2 multicast might break for some VLANs. Therefore, it is the responsibility of network administrators to configure a feasible number of VLANs in a VLAN group.
For the VLAN Groups feature to work as expected, the VLANs mapped in a group must be present in the controller.
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The VLAN Groups feature works for access points in local mode.
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The VLAN Groups feature works only in central switching mode and it cannot be used in FlexConnect local switching mode.
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ARP Broadcast feature is not supported on VLAN groups.
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VLAN group Multicast with VLAN group is only supported in local mode AP. Multicast VLAN is required when VLAN group is configured and uses multicast traffic.
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While you configure VLAN groups with multiple VLANs and each VLAN is used by a different subnet, clients having static IP addresses might be assigned to a wrong VLAN if SVIs are not present on the controller. Hence, for every VLAN that belongs to the VLAN group, ensure that you configure an SVI interface with a valid IP address.