[RT-AC87] Slower speeds through router and IPv4/IPv6

[mikec8785]

OK, just to start off this is my first post and I'm not super tech-literate although I know enough to get in trouble.

I just recently purchased the RT-AC87 and set it up with my Motorola SB6120 router with Comcast 105 Mbps internet. When I connect directly to the modem I get speeds approaching 100 Mbps, however when I then connect the modem to the router and hardwire my laptop to the router then run the same test I consistently get 30-40 Mbps less. What would be the reason for this? I turned off QoS and App Analysis.

Also, when working with Comcast support they had me use their own speedtest website that was something like comcast.speedtest.net. Using this site, when I was connected directly to the modem the test would run twice and provide results for IPv4 and IPv6. However, when I connect through the router and run that test I only get results for IPv4. Is there a reason for this? Could it be the reason why I'm seeing lower speeds through the router?

Thanks for any thoughts or help.

Also, somewhat related, but when I had QoS enabled I only got 5/5 down/up on the speed tests. I had to turn off QoS to get maximum speeds. Is there something wrong with my setup for QoS?

Edit: I went through settings and found that I did not have IPv6 enabled on the router. After setting that up the Comcast speed test then showed results for both IPv4 and IPv6 like when I was connected directly to the modem. However, I'm still showing slower speeds through the router.

 

[sfx2000]

Are you using Comcast's DNS or third party (OpenDNS/Google/Neustar/etc...).

 

[mikec8785]

Are you using Comcast's DNS or third party (OpenDNS/Google/Neustar/etc...).

I assume Comcast's DNS since I have not changed anything.