My company just changed it's old firewall (Zyxel ZyWALL 70) with a new one (Zyxel ZyWALL USG 300).
Everything seems to be working fine but sometimes, in a non-periodic span of time, connectivity seems to drop.
Web navigation stops, ftp uploads get interrupted and email checking fails.
EDIT: The interruption lasts 10-15 seconds.
Everything works if we plug the old firewall, so we are trying to understand what might cause the problem.
Connection is not dial-up with firewall but via ethernet with an external modem (unchanged from previous configuration).
Accordingly to log, WAN interface is never shut down.
How can we track down the issue?
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