Canon IB4000 series Online Manual page 356

Make sure that the firewall of the security software is disabled.
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If the firewall function of your security software is turned on, a message may appear warning that Canon
software is attempting to access the network. If the warning message appears, set the security software to
always allow access.
If using any programs that switch the network environment, check their settings. Some programs will enable a
firewall by default.
When using a router, connect the printer and computer to the LAN side (same
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network segment).
When the printer is connected to an AirPort Base Station via a LAN, use
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alphanumeric characters for the name of the network (SSID).
If the problem is not resolved, perform setup again according to the instructions on our website.
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