I have a new Sophos XG115 without any firewall rule besides the default one, with a basic license, default webfilters and no IPS activated. It is connected to a router and to a internal switch. Both interfaces have 1000 Mbps - Full Duplex Auto-negotiated. When I make a speed test I'm at around 30 Mbps Up and Down. But when I try to open a website, it takes 15 seconds or more. Before we set up the firewall it was much faster. Also over the old WLAN, who is not behind the firewall it is much faster as well.
Any idea what could cause that?
I had the same issue where the download speed slows down when using the XG 105 firewall.
How I fixed the slow issue was to update the Firewall Rule used by LAN users.
Firewall -> Edit User/Network Rule -> Advanced, Intrusion Prevention -> set to None