Hi,
It will be a pleasure to assist you with your request :-)
The attached diagram displays a point of failure, if you Core device is down, your entire network will be affected. Always try to have high availability, redundancy, scability, security, performance.
You could use the 3 layered model: Core, Distribution and Access. Also have a couple of switches for the server farm. Collapsed core model with access switches also could be used.
Firewalls can be used on the perimeter to protect your network of attacks from outside.
These links can be useful:
http://www.networkcomputing.com/data-centers/campus-network-design-models/1685370612
https://www.google.com/search?q=cisco+enterprise+architecture+model&client=firefox-b&biw=1366&bih=659&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0ahUKEwiHnsSE4YPSAhVC4CYKHeXXBL4QsAQIIg#imgrc=a_T9lKu-QO98MM:
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