Assuming your MS425 units are co-located, stacking cables would be MA-CBL-40G-1M (1 metre version). -50CM or -3M versions are also available. https://meraki.cisco.com/wp-content/uploads/2020/05/meraki_datasheet_sfp.pdf If they are more widely separated (unlikely, if you're replacing a sigle chassis), look at using Flexible Stacking, via fibre links: https://documentation.meraki.com/MS/Stacking/Switch_Stacks#Understanding_Flexible_Stacking You should look into using OSPF as an alternative dynamic routing protocol, supported by the MS425s (and the 355s, if you need to route on those too). You will need to look into what other routers / layer-3 switches the 4500 is currently exchanging routes with using EIGRP and possibly transition them to OSPF too. Likewise any other routers, beyond, in the same EIGRP setup. I'd also check whether a full routing protocol is really needed. Often, if you're on the periphery of a larger network you can achieve similar outcomes using (say) a static route or routes to a virtual IP address (a pair of routers running HSRP / VRRP, for example). Not sure what else you may have, switching-wise, downstream of the 4500, by way of access switches, but you will want to check out the Spanning Tree setup; MS switches do not support the proprietary PVST / PVST+ that Catalyst switches are usually running. https://documentation.meraki.com/MS/Meraki_Campus_LAN%3B_Planning%2C_Design_Guidelines_and_Best_Practices#STP_in_a_Hybrid_LAN I'd recommend you hook up with an experienced Cisco Partner to help you with this project.
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