Controller Based WLANs

Environment- Typically in a High density populated with good number of users configured with VLAN pooling on the VAP profile

Answer- 

• When ‘preserve-vlan’ knob is enabled for a ‘virtual-ap’, the controller can try to retain the VLAN ID for the client by looking up the client MAC in the bridge table.
• If the entry is found, the controller will retain the VLAN for the client. If an entry is not found, the controller may allocate a new VLAN ID for the client.

Configuration
 
(Aruba-testlab) (config) #wlan virtual-ap test
(tac-rap.arubanetworks.com) (Virtual AP profile "test") #?
preserve-vlan           Preserve Client VLAN Across VLAN Pool Change
 
Sample config below:
 
wlan virtual-ap "LAB"
   aaa-profile "LAB"
   ssid-profile "certify2"
   vlan “LAB”
   allowed-band g
   broadcast-filter all
   blacklist-time 900
   no mobile-ip
   preserve-vlan
 
Use-case
 

1. In High-density populated network we may need to use the VLAN pooling (Hash or Even) for client distribution to limit broadcast and multicast on each and every VLAN and load-balance the clients across VLAN`s.
2. Use case would be when clients connected initially on one VLAN and dropped off/de-authenticated and came back within the lease time client would maintain the same VLAN by not doing the DHCP and go to different VLAN.
3. By this way, we could preserve Client VLAN  which would be of great help as it is possible in a busy environment Smart phone was just used for few min, then goes offline and may come back again after few mins.