Имеется стек 3120-24SC и к нему ЛАГом на 8 портов подключён 3620.
Настройки привожу ниже.
И там и там отключён STP.
Но периодически, вне зависимости от нагрузки, на ЛАГе появляются дропы по STP. Откуда они берутся?

Command: show stack_device

Box ID Box Type H/W Version Serial Number
------ ---------------- ----------- --------------------
1 DGS-3120-24SC A2 R3143CB000044
2 DGS-3120-24SC A2 R3143C9000347
3 DGS-3120-24SC A2 R3143D7000456
4 DGS-3120-24SC A2 R3143CB000009
5 DGS-3120-24SC B1 R3144E7000084

Command: show stp

STP Bridge Global Settings
---------------------------
STP Status : Disabled
STP Version : RSTP
Max Age : 20
Hello Time : 2
Forward Delay : 15
Max Hops : 20
TX Hold Count : 6
Forwarding BPDU : Disabled
New Root Trap : Disabled
Topology Change Trap : Disabled
NNI BPDU Address : dot1d


Command: show link_aggregation

Link Aggregation Algorithm = IP-Source-Dest

Group ID : 3
Type : LACP
Master Port : 4:1
Member Port : 4:1-4:8
Active Port : 4:1-4:8
Status : Enabled
Flooding Port : 4:1
Trap : Disabled

Command: show lacp_port 4:1-4:8


Port Activity

----- --------
4:1 Passive
4:2 Passive
4:3 Passive
4:4 Passive
4:5 Passive
4:6 Passive
4:7 Passive
4:8 Passive
==============================

Command: show switch

Device Type : DGS-3620-28TC Gigabit Ethernet Switch
MAC Address :
IP Address :
VLAN Name : MGMT
Subnet Mask :
Default Gateway :
Boot PROM Version : Build 1.00.016
Firmware Version : Build 2.70.B003
Hardware Version : B1
Firmware Type : EI
Serial Number : PVW83DA000009

Command: show stp

STP Bridge Global Settings
---------------------------
STP Status : Disabled
STP Version : RSTP
Max Age : 20
Hello Time : 2
Forward Delay : 15
Max Hops : 20
TX Hold Count : 6
Forwarding BPDU : Disabled
New Root Trap : Enabled
Topology Change Trap : Enabled
NNI BPDU Address : dot1d

Command: show link_aggregation

Link Aggregation Algorithm = IP-Source-Dest

Group ID : 1
Type : LACP
Master Port : 1
Member Port : 1-8
Active Port : 1-8
Status : Enabled
Flooding Port : 1
Trap : Disabled

Command: show lacp_port 1-8


Port Activity LACP Timeout

----- -------- -----------
1 Active Short
2 Active Short
3 Active Short
4 Active Short
5 Active Short
6 Active Short
7 Active Short
8 Active Short
===========================

DGS-3620-28TC:admin#show error ports 1-8
Command: show error ports 1-8

Port number : 1
RX Frames TX Frames
--------- ---------
CRC Error 0 Excessive Deferral 0
Undersize 0 CRC Error 0
Oversize 0 Late Collision 0
Fragment 0 Excessive Collision 0
Jabber 0 Single Collision 0
Symbol Error 0 Collision 0
Buffer Full Drop 0 STP Drop 115951
ACL Drop 0 HOL Drop 2743834
Multicast Drop 0 COS0 HOL Drop 0
VLAN Ingress Drop 500102 COS1 HOL Drop 0
Invalid IPv6 0 COS2 HOL Drop 2743834
STP Drop 79220 COS3 HOL Drop 0
Storm and FDB Discard 0 COS4 HOL Drop 0
MTU Drop 0 COS5 HOL Drop 0
COS6 HOL Drop 0
COS7 HOL Drop 0

дык у вас же Forwarding BPDU : Disabled
вот BPDU и дропаются