Loop detected after rebooting primary core switch

[Lourdes]

Our network has 2 Firewalls (Primary & Spare) and 2 Core Switches (Primary and Secondary). Our client decided to reboot the primary core switch because they are experiencing network dropout for several days now. After rebooting, the 2 firewalls suddenly lost connection and start having a rainbow light color. The network went back but we check the logs and there are several loops detected connected to the primary core switch. Is it because we reboot the primary core switch? Is this normal? 

[cmr]

How are the firewalls connected to the switches (how many connections) and how are the switches connected to each other?  If you have multiple links then spanning tree could be blocking the wrong ports.

[Lourdes]

Here is our network diagram.

 

Most of the POE and Non-POE switches are connected to end-users. A loop guard is enabled to all ports for POE, Non-POE, WAN switch, and server switch. And all ports at the Core primary and Secondary are in RSTP forwarding state.

[cmr]

@Lourdes I'd disable the two links below as long as the link marked cascade is either a normal trunk between the switches or a stacking cable. Then let us know what happens.

 

[Lourdes]

Hi cmr,

Thank you for the advice. Will try that and update you.

Regards,

Lourdes,