Hmm,  Why don't you try setting your spanning-tree priority,  eg. spanning-tree priority 4096  (Use multiple of 4096 if you choose a larger value.) Or  Possibly block smtp bpdu's from being sent on the port to your ISP.  Edit the the port in question, then type in:  spanning-tree disable    I see the Cisco equivalent is 'spanning-tree bpdufilter enable'.  /Nick
Hello!I can not understand strange problem which is happening on our Powerconnect 6224.We have small network. Powerconnect is our main switch, which is connected to our ISP. Every day in log file I see Spanning Tree Protocol messages like this:      14       5304446     Notice     APR 24 00:03:34     TRAPMGR     %% New Spanning Tree Root: 0, Unit: 1             15       5304447     Notice     APR 24 00:03:34     TRAPMGR     %% Unit 1 elected as the new STP root            16       5304448     Notice     APR 24 00:03:34     TRAPMGR     %% Instance 0 has elected a new STP root: 8000:aaaa:bbbb:4ef3            17       5304449     Notice     APR 24 00:03:34     TRAPMGR     %% Unit 1 Port 1 is transitioned from the Forwarding state to the Blocking state in instance 0            18       5304450     Notice     APR 24 00:03:34     TRAPMGR     %% Unit 1 Port 1 is transitioned from the Learning state to the Forwarding state in instance 0            19       5304451     Notice     APR 24 00:03:35     TRAPMGR     %% Link Down: VLAN- 2            20       5304452     Notice     APR 24 00:03:35     TRAPMGR     %% Link on VLAN- 2 is failed            21       5304453     Notice     APR 24 00:03:35     TRAPMGR     %% Link Up: VLAN- 2            22       5304456     Notice     APR 24 00:03:35     TRAPMGR     %% Instance 0 has elected a new STP root: 8000:yyyy:cccc:3300            23       5304457     Notice     APR 24 00:03:35     TRAPMGR     %% Unit 1 Port 11 is transitioned from the Forwarding state to the Blocking state in instance 0            24       5304458     Notice     APR 24 00:03:35     TRAPMGR     %% Unit 1 Port 18 is transitioned from the Forwarding state to the Blocking state in instance 0            25       5304459     Notice     APR 24 00:03:36     TRAPMGR     %% Unit 1 Port 18 is transitioned from the Learning state to the Forwarding state in instance 0            26       5304485     Notice     APR 24 00:04:05     TRAPMGR     %% Unit 1 Port 11 is transitioned from the Learning state to the Forwarding state in instance 0aaaa:bbbb:4ef3 is ours Dell MACyyyy:cccc:3300 is ISP main switch MAC (where our Dell on port 1 is connected).The only member of VLAN2 is Port 1.Switch configuration see below.Why the STP root changes from one switch to another and then back again?   Configuration: !Current Configuration:!System Description "Dell 24 Port Gigabit Ethernet, 2.2.0.3, VxWorks5.5.1"!System Software Version 2.2.0.3!configurevlan databasevlan  2-3,24ip igmp snooping 3exithostname "SciDell"sntp unicast client enablesntp client poll timer 1024sntp server 83.64.124.251 priority 2sntp server 147.231.19.43clock timezone 2 minutes 0 zone "EET"stackmember 1 1exitip address 192.168.2.1 255.255.255.0ip address vlan 24logging buffered size 300ip routingip route 0.0.0.0 0.0.0.0 X.Y.Z.161bootpdhcprelay enablebootpdhcprelay maxhopcount 3bootpdhcprelay serverip X.Y.Z.167interface vlan 1bridge multicast forbidden forward-unregisteredexitinterface vlan 2bridge multicast forbidden forward-unregisteredbridge multicast forbidden address 0100.5E01.000C add ethernet 1/g1bridge multicast forbidden address 0100.5E01.000D add ethernet 1/g1bridge multicast forbidden address 0100.5E01.000E add ethernet 1/g1bridge multicast forbidden address 0100.5E40.000A add ethernet 1/g1bridge multicast forbidden address 0100.5E40.000B add ethernet 1/g1name "Uplink"routingip address  X.Y.Z.171  255.255.255.224no ip proxy-arpexitinterface vlan 3bridge multicast forbidden forward-unregisteredbridge multicast address 0100.5E7F.FFFAname "CPE"routingip address  X.Y.Z.1  255.255.254.0no ip proxy-arpip igmpexitinterface vlan 24name "Management"exitip igmpusername "aaaa" password f6db467628f299049005d10cd6335569 level 15 encryptedbridge multicast filteringip igmp snooping!interface ethernet 1/g1spanning-tree cost 20000spanning-tree portfastswitchport access vlan 2exit!interface ethernet 1/g2spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g3spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g4spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g5spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g6spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g7spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g8spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g9spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g10spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g11spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g12spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g13spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g14spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g15spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g16spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g17spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g18spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g19spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g20spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g21spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g22spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g23spanning-tree cost 20000spanning-tree portfastswitchport access vlan 3exit!interface ethernet 1/g24spanning-tree portfastswitchport access vlan 24exit!interface ethernet 1/xg1switchport access vlan 3exit!interface ethernet 1/xg2switchport access vlan 3exit!interface ethernet 1/xg3switchport access vlan 3exit!interface ethernet 1/xg4switchport access vlan 3exit!interface port-channel 1switchport access vlan 2exit!interface port-channel 2switchport access vlan 3exit!interface port-channel 3switchport access vlan 3exit!interface port-channel 4switchport access vlan 3exit!interface port-channel 5switchport access vlan 3exit!interface port-channel 6switchport access vlan 3exit!interface port-channel 7switchport access vlan 3exit!interface port-channel 8switchport access vlan 3exit!interface port-channel 9switchport access vlan 3exit!interface port-channel 10switchport access vlan 3exit!interface port-channel 11switchport access vlan 3exit!interface port-channel 12switchport access vlan 3exit!interface port-channel 13switchport access vlan 3exit!interface port-channel 14switchport access vlan 3exit!interface port-channel 15switchport access vlan 3exit!interface port-channel 16switchport access vlan 3exit!interface port-channel 17switchport access vlan 3exit!interface port-channel 18switchport access vlan 3exit!interface port-channel 19switchport access vlan 3exit!interface port-channel 20switchport access vlan 3exit!interface port-channel 21switchport access vlan 3exit!interface port-channel 22switchport access vlan 3exit!interface port-channel 23switchport access vlan 3exit!interface port-channel 24switchport access vlan 24exitsnmp-server group readr v1 read Defaultsnmp-server group readr v2 read Defaultsnmp-server community-group readr readrexit
Spanning tree protocol root changes problem