Ports go down adding a 9200L to mixed vendor and Spanning-Tree NW

[Startzc]

I've been tasked to assist a local technician to replace legacy Avaya switches with new Cisco 9200L switches for an air gapped network that is only used for ACS, IDS, and CCTV. Because of what this network controls, our maintenance window, max 4 hours per night Sun to Thur only, is not long enough to swap out all of the legacy switches with Cisco switches, so we have to be able to swap out 1 or 2 at time to leave time to troubleshooting and/or reinstall the old switches if needed.

The existing network contains the legacy Avaya switches, plus Allied Telesis, Cisco IE4000's, and Hirschman industrial switches. The core/distribution switch is an an Allied Telesis 930x L3 switch with 5 fiber trunks to the legacy Avaya switches. The old Avaya access switch for the building where the core switch is located has also been replaced with an Allied Telesis X530L. Routing is done only at the Core L3 Switch using Virtual Interfaces as the gateway and static routes for each VLANs Subnet. All other switches have an all 0's default route with the destination as the VLAN1 interface as gateway IP. You can see the network layout, VLAN info, and STP versions below or in the attached NW diagram jpeg.

• VLAN1 is Native VLAN and is used for all Servers and CCTV traffic,
• VLAN2 is Primary ACS and IDS traffic and some servers have dual NIC's with a VLAN2 address also,
• VLAN3 is Backup ACS and IDS traffic,
• VLAN323 is Used for remote MGMT of IE4000's,
• Avaya Switches are MSTP,
• Allied Telesis Core L3 Switch is MSTP,
• Allied Telesis Access Switch is RSTP,
• Cisco 3560G are PVST,
• IE4000's and 9200L's are Rapid-PVST.

My next test is planned to be changing everything to MSTP and trying that. Any help identifying if I am on the right track or alternative ideas are welcome. Please and thank you.

[Startzc]

Deleted because I was able to add to original message.

[balaji.bandi]

couple of suggestions :

1. first decide where you want to be root for the STP

2. check the STP loops and enable control root port

3. configured best for your requirement with multi-vendor support of STP.

some guide lines :

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html

[Startzc]

I don't know how to check the loops, I don't understand how there could be loops in a Star network with no redundant links. Another big issue is that because of where this system is, there is no cellular signal or wi-fi available to research on the fly. Everytime something doesn't work or we get some piece of new information to research it takes us 45 minutes just to exit the building and get to an area with internet access.

[Startzc]

After replacing all the Avaya switches, we were able to get everything working between Allied Telesis and Cisco configuring MSTP, but because of poor design we still have to use VLAN1 and MSTP Instance 0. I am going back next week to try and switch everything over to PVST+ and RSTP because we have started getting occasional port flapping one of the switches connected to the core, the one that happens to have the most end devices and other switches daisy-chained behind it.