Switch Problem, every 2 Hours Port is down

[romanegger]

Dear Cisco Friends

I got a puzzle for you. 

I'm currently experiencing weird Network behaviour. Every 2 hours there is a interruption of the network on a port, after i changed the topology

(01.07 16:00)

What you think might be the issue?

STP = spanningtree

PC = portchannel

I checked Spanning Tree and there is no BPDUGuard activated on the Switch 1 port 5

Spanning tree is not working though, i couldnt find the issue yet.

Switch 1-4 are normal IOS-cisco switch

Switch 5 is a "cheap" SG300 Switch, with different properties for Spanning Tree.

If you would like to have some diagnostic command outputs just ask :)

Greetings, Roman

[romanegger]

Edit: Spanning tree is, of course, working between Switch 1 - 4.

But Switch 5 thinks he is the root. 

Spanning Tree is activated on both switches.

[romanegger]

I have some news regarding the events happening on the switch:

Jul  2 09:12:47.899: pm_extern_port_link_event: link-down on Gi0/5
Jul  2 09:12:47.899:     pm_port 1/5: during state trunk, got event 5(link_down)
Jul  2 09:12:47.899: @@@ pm_port 1/5: trunk -> pagp
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 1, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 2, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 3, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 4, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 10, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 11, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 20, port_id 128.5
Jul  2 09:12:47.916: Found no corresponding dummy port for instance 21, port_id 128.5
Jul  2 09:12:47.924: *** port_modechange: 1/5 mode_none(10)
Jul  2 09:12:47.924: @@@ pm_port 1/5: pagp -> dtp
Jul  2 09:12:47.924: pm_flap_timer_stop: Gi0/5 pagp
Jul  2 09:12:47.924: *** port_bndl_stop: 1/5 : inform yes
Jul  2 09:12:47.924: @@@ pm_port 1/5: dtp -> present
Jul  2 09:12:47.924: *** port_dtp_stop: 1/5
Jul  2 09:12:47.924: pm_flap_timer_stop: Gi0/5 pagp
Jul  2 09:12:47.924: pm_flap_timer_stop: Gi0/5 dtp
Jul  2 09:12:47.924: pm_flap_timer_stop: Gi0/5 unknown
Jul  2 09:12:47.924: *** port_linkchange: reason_link_change(3): link_down(0)1/5
Jul  2 09:12:47.924:     pm_port 1/5: idle during state present
Jul  2 09:12:47.924: @@@ pm_port 1/5: present -> link_down
Jul  2 09:12:47.941:     pm_port 1/5: during state link_down, got event 29(pruning) (ignored)