Go to System>Preferences>Network Connections. This will bring up the configuration window. You'll notice several tabs at the top. Make sure you are on the correct one (Probably wired). Then you will will see "Auto Ethernet." Click on it and then click "Edit" which will bring up another window. Then click the tab labeled "IPv4 Settings." Then under the "Method" drop down, you'll have to select "Manual." Then you can click "Add" to add an IP address and enter it with the Netmask and Gateway accordingly. To get everything to work properly, you'll need the IP, Netmask, Gateway, and at least 1 DNS server. entered here.
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Go to System>Preferences>Network Connections. This will bring up the configuration window. You'll notice several tabs at the top. Make sure you are on the correct one (Probably wired). Then you will will see "Auto Ethernet." Click on it and then click "Edit" which will bring up another window. Then click the tab labeled "IPv4 Settings." Then under the "Method" drop down, you'll have to select "Manual." Then you can click "Add" to add an IP address and enter it with the Netmask and Gateway accordingly. To get everything to work properly, you'll need the IP, Netmask, Gateway, and at least 1 DNS server. entered here.