15.0 SE5 DHCP snooping bug

CISCO 2960  IOS 15.0(2) SE5

Switch Ports Model              SW Version            SW Image                 
------ ----- -----              ----------            ----------               
*    1 50    WS-C2960+48TC-L    15.0(2)SE5            C2960-LANBASEK9-M        

Configuration register is 0xF

配置 DHCP snooping后，show ip dhcp snooping 显示都正常

XYJ-C2960_11#show ip dhcp snooping 
Switch DHCP snooping is enabled
DHCP snooping is configured on following VLANs:
1-100
DHCP snooping is operational on following VLANs:
1-2,4-18,20-25,100
DHCP snooping is configured on the following L3 Interfaces:

Insertion of option 82 is enabled
   circuit-id default format: vlan-mod-port
   remote-id: 84b5.17ea.5c80 (MAC)
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Verification of giaddr field is enabled
DHCP snooping trust/rate is configured on the following Interfaces:

Interface                  Trusted    Allow option    Rate limit (pps)
-----------------------    -------    ------------    ----------------   
GigabitEthernet0/1         yes        yes             unlimited
  Custom circuit-ids:
GigabitEthernet0/2         yes        yes             unlimited
  Custom circuit-ids:
Port-channel1              yes        yes             unlimited
  Custom circuit-ids:

但是untrust口依然放行 DHCP offer包，
并且在  show  ip dhcp snooping binding 没有显示任何有效条目

XYJ-C2960_11#show ip dhcp snooping binding 
MacAddress          IpAddress        Lease(sec)  Type           VLAN  Interface
------------------  ---------------  ----------  -------------  ----  --------------------
Total number of bindings: 0

XYJ-C2960_11#
XYJ-C2960_11#

最后去google一下，才知道这是该版本的一个BUG
url1  url2
只能通过升级上去解决问题。