I have Cisco AP Aironet 1100 and I have 5 vlans in my network as the fallowing:

vlan101 with name (APmangm101)
vlan4 with name (Voice4)
vlan6 with name (User6)
vlan8 with name (inter8)

and vlan100 is native vlan

step1
I configured the SSID and Map it to respective VLANs (vlan4,vlan6,vla8)as the fallowing:

Dot11 ssid Voice4
vlan 4
authentication open
authentication key-managment wpa
wpa-psk ascii admin4444
mbssid guest-mode
exit

Dot11 ssid User6
vlan 6
authentication open
authentication key-managment wpa
wpa-psk ascii admin666
mbssid guest-mode
exit

Dot11 ssid inter8
vlan8
authentication open
authentication key-managment wpa
wpa-psk ascii admin888
mbssid guest-mode
exit

Step 2
Assigning the encryption to different SSIDs with repective Vlans.

int dot11Radio 0
mbssid
encryption vlan 4 mode ciphers aes-ccm
encryption vlan 6 mode ciphers aes-ccm
encryption vlan 8 mode ciphers aes-ccm
ssid Voice4
ssid User6
ssid inter8

Step 3
Configuring the sub interface for Dot11 radio 0 and Ethernet

interface Dot11Radio0.100
encapsulation dot1Q 100 native
bridge-group 100
exit

interface fastethernet0.100
bridge-group 100
encapsulation dot1Q 100 native
exit

interface Dot11Radio0.101
encapsulation dot1Q 101
bridge-group 101
exit

interface fastethernet0.101
bridge-group 101
encapsulation dot1Q 101
exit

interface Dot11Radio0.4
encapsulation dot1Q 4
bridge-group 4
exit

interface fastethernet0.4
bridge-group 4
encapsulation dot1Q 4
exit

interface Dot11Radio0.6
encapsulation dot1Q 6
bridge-group 6
exit

interface fastethernet0.6
bridge-group 6
encapsulation dot1Q 6
exit

interface Dot11Radio0.8
encapsulation dot1Q 8
bridge-group 8
exit

interface fastethernet0.8
bridge-group 8
encapsulation dot1Q 8
exit

bridge irb
bridge 1 route ip
exit

Step 4
Configuration on the switch

int g1/0/3
switchport mode trunk
switchport trunk native vlan 100
switchport trunk allowed vlan 100,101,4,6,8
exit

=======================================================
My question:
1-The AP is work with Multi SSID and I can connect to any SSID and and do ping to any network, but when try to do ping to AP's IP management (172.16.101.20) I can't do it and can't access ass webpage to AP?
2-whene I type this command (At the bottom) the AP is disconnect and I can't ping to it even reload it:

 interface fastethernet0.100
 bridge-group 100

why it disconnect?
 
Note:
interface BVI1
 ip address 172.16.101.20 255.255.255.0

 ip default-gateway 172.16.101.254