I was helping my friend again with his Mac he complained his internet speed is not as advertised. I went ahead and tested my internet speed via Ethernet and I resulted 250 Mbps from fast.com When testing his Apple iMac Pro I only resulted in 50 Mbps via Ethernet. I was baffled, I went ahead changed/checked the following:
- Changed the MTU. No improvement
- Manually set IP. No improvement
- Changed Ethernet cable to a fancy CAT-7 cable. No improvement
- Checked to see if there was any malware or viruses. None.
- Nothing was downloading.
- Checked if there was any issue with the writing speed on the SSD. Writing speed was good.
The breakthrough was when I decided to ping to google.com on my Windows laptop. What I realized was that I was getting IPv6 from google.com instead of IPv4.
So I decided to go back into the Ethernet settings and enable IPV6 since it was not enabled
Steps to enable IPv6:
- Apple menu
- System Preferences
- Choose your connection type. For me it was Ethernet
- Advanced Button
- Select the TCP/IP
- Change the Configure IPv6 drop-down box from Off to Automatically.
After enabling IPV6, I speed test the iMac and to my surprise it was finally getting 200+ Mbps. I decided to turn off IPv4 and use IPv6 alone, but unfortunately that did not work. So I left IPv4 on. Most likely when he configured his network, he accidentally enabled IPv6. At the same time I’m pretty baffled on why IPv4 is slower than IPv6.Almost 4x as slow. Maybe he configured his network wrong and so the IPv4 takes a longer route to respond? Or maybe IPv6 once enabled has a higher priority than IPv4? I decided to leave it as is since he was happy the internet was finally up to its advertised speed. Hopefully, this post becomes helpful for someone with a similar issue.