Office Expansion (adding Distribution layer) and Layer2/3 topology

Hello there.

Our main office building is currently composed of a pair of 4500-X (32 port + 8 port expansion) in VSS functioning as a collapsed core/distribution. We have about 15 stacks of 2960X-s hanging off it. LAN is Layer 2 to the edge, WAN is BGP + some local sites using OSPF.

We are now running out of ports on the 4500-Xs and need to add a dedicated distribution layer. Any thoughts on keeping the Layer 2 topology or converting to Layer 3 to distribution layer (or all the way to access?). Also any thoughts of which type of switch for distribution or follow the CVD (https://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Campus/CVD-Campus-LAN-WLAN-Design-Guide-2018JAN.pdf) ?

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Regards

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