Spantree loops

[mkerem1]

Hi all,

In a large project that we are trying to put into operation, we are using Alcatel products. As can be seen in the attached drawing, OS6900 series backbones are used in two separate locations defined by VRRP in the system. There are two rings between the two backbones, one going over the buildings and the other directly connected. In the distribution buildings, there are OS6465 U28X and P28 L2 Edge switches. All lines in both rings are working with 10G. VRRP is working properly, but as a result of our Spanning Tree application, when we connect both lines at the same time, the network goes down.

spantree mode flat
spantree vlan 1 admin-state enable
spantree vlan 601 admin-state enable
spantree vlan 602 admin-state enable
spantree vlan 603 admin-state enable
spantree vlan 604 admin-state enable
spantree vlan 609 admin-state enable
spantree vlan 611 admin-state enable
spantree vlan 612 admin-state enable
spantree vlan 618 admin-state enable
spantree vlan 620 admin-state enable
spantree vlan 621 admin-state enable
spantree vlan 622 admin-state enable
spantree vlan 623 admin-state enable
spantree vlan 624 admin-state enable
spantree vlan 625 admin-state enable
spantree vlan 626 admin-state enable
spantree port 1/1/1 loop-guard enable
spantree port 1/1/2 loop-guard enable
spantree port 1/1/3 loop-guard enable
spantree port 1/1/4 loop-guard enable

Spanning tree is defined in this way for all switches in the field. Ports 1-4 are the uplinks to which the rings are connected. On the backbone (192.168.100.2) side, ports 41 and 43 are uplink ports.

spantree mode flat
spantree vlan 1 admin-state enable
spantree vlan 601 admin-state enable
spantree vlan 602 admin-state enable
spantree vlan 603 admin-state enable
spantree vlan 604 admin-state enable
spantree vlan 609 admin-state enable
spantree vlan 611 admin-state enable
spantree vlan 612 admin-state enable
spantree vlan 618 admin-state enable
spantree vlan 620 admin-state enable
spantree vlan 621 admin-state enable
spantree vlan 622 admin-state enable
spantree vlan 623 admin-state enable
spantree vlan 624 admin-state enable
spantree vlan 625 admin-state enable
spantree vlan 626 admin-state enable
spantree port 1/1/41 loop-guard enable
spantree port 1/1/43 loop-guard enable

When we plug in both ports, the same MAC address attacks both ports. When i looked to logs, I see too many "arp info overwritten"
I need your valuable suggestions on how to solve this problem.

Regards..

[silvio]

A lot of missing informations....
How is the priority configured - especially at the both cores?
Are all tagged and untagged vlans configured at the uplinks between all switches in the same way?
Please disable loop-guard and test it again.
Check STP at all switches with "show spantree cist"
Is there any blocked port: show spantree port blocked/active?
BR Silvio

[mkerem1]

Thanks for reply,

We have solved the problem. When I checked building switch configs, Flat mode not defined.
And also I changed priorities of spantrees. Then it worked properly (As you said)
Thanks for your interest..