Ethernet Tap & Wireshark

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Hello, First let me say Thank You for your time and effort in response to my problem. I am using a Ethernet Tap on my own network, It works 50/50. My question is : why do certain websites like www.unb.ca ..... appear on my packet sniffing. & other sites like www.gbc.ca or www.toronto.ca .... do not appear at all.

P.S. I am doing this as a project. Thank You.