Your software release may not support all the features documented in
this module. For the latest caveats and feature information, see Bug Search
Tool and the release notes for your platform and software release. To find
information about the features documented in this module, and to see a list of
the releases in which each feature is supported, see the feature information
table at the end of this module.
Use Cisco Feature Navigator to find information about platform support
and Cisco software image support. To access Cisco Feature Navigator, go to
http://www.cisco.com/go/cfn. An account on Cisco.com is
A VLAN should be present in the
to be able to add it to the VLAN group.
For VLAN group to function properly, in addition to enabling DHCP
snooping globally, you must ensure that DHCP snooping is enabled in all the
Restrictions for VLAN Groups
The number of VLANs mapped to a VLAN group is not limited by Cisco IOS Software Release. But if the number of VLANs in a VLAN group exceed the recommended value of 32, the mobility behavior is unexpected and in the VLAN group, L2 multicast breaks for some VLANs. So it is the responsibility of the administrator to configure feasible number of VLANs in a VLAN group. When a VLAN is added to a VLAN group mapped to a WLAN which already has 32 VLANs, a warning is generated. But when a new VLAN group is mapped to a WLAN with more than 32 VLANs, an error is generated.
For expected behavior of the VLAN group, the VLANs mapped in the group must be present in the controller. The static IP client behavior is not supported.
Whenever a client
connects to a wireless network (WLAN), the client is placed in a VLAN that is
associated with the WLAN. In a large venue such as an auditorium, a stadium, or
a conference room where there are numerous wireless clients, having only a
single WLAN to accommodate many clients might be a challenge.
The VLAN group
feature uses a single WLAN that can support multiple VLANs. The clients can get
assigned to one of the configured VLANs. This feature maps a WLAN to a single
VLAN or multiple VLANs using the VLAN groups. When a wireless client associates
to the WLAN, the VLAN is derived by an algorithm based on the MAC address of
the wireless client. A VLAN is assigned to the client and the client gets the
IP address from the assigned VLAN. This feature also extends the current AP
group architecture and AAA override architecture, where the AP groups and AAA
override can override a VLAN or a VLAN group to which the WLAN is mapped.
system marks VLAN as "dirty" for 30 minutes when the clients are unable to
receive IP address using DHCP. The system might not clear the "dirty" flag from
the VLAN even after 30 minutes for a VLAN group. This is expected behavior
because the timestamp of each interface has to be checked to see if it is
greater than 30 minutes, due to which there is a lag of 5 minutes for the
global timer to expire.
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