Interface IP - <This is my question> 10.40.20.1? I supose you mean 10.10.20.1 but thats currently in use at your core. That is a ip thats not in subnet 10.10.20.0/22 https://documentation.meraki.com/MS/Layer_3_Switching/MS_Layer_3_Switching_and_Routing#Initializing_Layer_3_Routing To start using layer 3 routing, navigate to the switch details page by going to Switch > Monitor > Switches and clicking on the switch to be configured. Under Status > L3 routing status, click Configure layer 3 settings. The window that appears will allow the configuring of the first routed interface and a default route. It is recommended that the uplink VLAN be configured first The default route will be pointing to the default gateway adress of you first interface
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