Change of Fortiswitch Topology - Ring to MCLAG

[erson]

We deployed our access switching (448D-POE) using the ring topology several years ago but now want to change to using Tier-3 mclag with ICL's. I don't want to touch any of the ports that are currently connected to my switches, just the topology. Will the Fortigate keep the port configurations of each switch based on it's serial number?

My plan would be to disconnect all the ISL links, then follow the documentation and choose two switches in each closet to become the Tier-2 mclag. Then configure the remaining four switches to form Tier-3. But losing the port configurations would suck.

One follow up question - with the Tier-2 and Tier-3 mclag topology there is a limit to the number of switches that can be configured per IDF, if you use 448D switches. Each switch has only four SFP slots to support 10G optics. The Tier-2 switches each lose one for the uplink to Tier-1, then one for the ICL to it's peer, then two more - one for each downstream neighbor. There are no more 10G interfaces available. So if I wanted to have even one more switch in that closet I'd need to deploy a minimum of two and create a second Tier-2 mclag.

[Anthony_E]

Hello erson,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[Anthony_E]

Hello erson,

We are still looking for someone to help you.

We will come back to you ASAP.

Regards,

[Anthony_E]

Hello erson,

Here the answer from one of our expert:

"The mclag trunks are based on serial numbers switch from fgate to downstream connection, but the trunk name between the ICLs on each tier changed by FlinkICL0*, 

[Thursday 3:42 PM] Elihu Hamud

He needs to connect one by one switch and wait 14 minutes more less to form the mclag on each tier. Otherwise a loop or malformation trunk will be on place.

Follow these guides:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Three-tier-MCLAG-configuration-on-managed/...

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Three-tier-MCLAG-configuration-on-managed/..."

Regards,

Anthony