[c-nsp] Strange behaviour spanning-tree on port

[Roman Shibrick]

Hi, all. At me is Cisco Catalyst 4507 Sup V. In logs I constantly see next lines:

...
Aug 25 09:30:29: Created spanning tree port Gi7/21 (18977BF8) for tree VLAN0178 (18B8B968)
Aug 25 09:30:29: Enabling spanning tree port: GigabitEthernet7/21 (18977BF8)
Aug 25 09:30:29: RSTP(178): initializing port Gi7/21
Aug 25 09:30:29: RSTP(178): Gi7/21 is now designated
Aug 25 09:31:01: Disabling spanning tree port: GigabitEthernet7/21 (18977BF8)
Aug 25 09:31:01: Deleting spanning tree port: Gi7/21 (18977BF8)
Aug 25 09:31:01: STP PVST: deleted vlan 178 intf 189EE290
Aug 25 09:31:04: Created spanning tree port Gi7/21 (18977BF8) for tree VLAN0178 (18B8B968)
Aug 25 09:31:04: Enabling spanning tree port: GigabitEthernet7/21 (18977BF8)
Aug 25 09:31:04: RSTP(178): initializing port Gi7/21
Aug 25 09:31:04: RSTP(178): Gi7/21 is now designated
Aug 25 09:31:35: Disabling spanning tree port: GigabitEthernet7/21 (18977BF8)
Aug 25 09:31:35: Deleting spanning tree port: Gi7/21 (18977BF8)
Aug 25 09:31:35: STP PVST: deleted vlan 178 intf 189EE290
...

HP server is included in the given port.
Port configuration is:

interface GigabitEthernet7/21
 description == Servers
 switchport access vlan 178
 switchport mode access
 switchport port-security
 switchport port-security maximum 2
 switchport port-security violation restrict
 switchport port-security mac-address sticky
 switchport port-security mac-address sticky 001e.0b4b.4056
 no keepalive
 spanning-tree portfast
 spanning-tree bpdufilter enable
 spanning-tree bpduguard enable
end

Why constantly there is rapid-pvst, pvst reinitialization on the given port? 

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0178         Desg FWD 4         128.405  Edge P2p
build15-CORE#sh spanning-tree interface gigabitEthernet 7/21 det
 Port 405 (GigabitEthernet7/21) of VLAN0178 is designated forwarding
   Port path cost 4, Port priority 128, Port Identifier 128.405.
   Designated root has priority 20658, address 001c.581f.9e80
   Designated bridge has priority 20658, address 001c.581f.9e80
   Designated port id is 128.405, designated path cost 0
   Timers: message age 0, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   The port is in the portfast mode
   Link type is point-to-point by default
   Bpdu guard is enabled
   Bpdu filter is enabled
   BPDU: sent 0, received 0


GigabitEthernet7/21 is up, line protocol is up (connected)
59200 packets input, 35164800 bytes, 0 no buffer
     Received 59200 broadcasts (0 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 input packets with dribble condition detected
     660390 packets output, 95397300 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out

Thanks. Roman