Anti ARP spoofing causing Internet slowdown

If I enable the anti ARP spoofing, the internet connection speed collapses.
So I don’t activate it and I surf without problems at a high speed. In my opinion it depends on the internet service provider (I use Vodafone Italy), so maybe with some ISPs it creates this effect maybe with other ISPs not, or it depends on the modem you use.

Edited Title

My provider is att and the modem is an Arris BGW210-700. I remember trying anti-ARP spoofing last year and it didn’t work then either. Strangely, since my last post in this thread, I’ve been having terrible connection problems, even though I’ve reverted my settings. I had to reply to another thread a little while ago from my phone because my PC wouldn’t load the Comodo forum. It’s like things went haywire. If I can post this, maybe things are settling down. Not enough wherewithall to troubleshoot this myself at this time, so I’ll probably just leave those settings alone.

Here are my speed test results.

I state that my PC is connected to the modem via WiFi.

Image 1 with active anti ARP spoofing.

Image 2 with anti ARP spoofing disabled.

My provider: Vodafone, router: easybox (!!!), problems: 0, connection: LAN

Yes, that’s a big difference in speed. We here in the US pay a lot of $$ for less internet, as you can see in the picture below.

It would be helpful to get a wireshark packet capture when opening a website with anti-arp spoofing disabled. Then save a second packet capture with anti-arp spoofing enabled.