slow download / upload with ipv6 enabled

[Mrgoodall]

My Equipment:
RBK50
Netgear CM1000
GB service with Xfinity

So, i recently upgraded to Xfinity GB service, was previously on 450MB tier. Noticed though that speedtests were roughly the same pre/post service upgrade (350-500MB). I hardwired into the CM1000 and was getting 978MB+ on speedtests, but Wifi stayed in the (350-500MB) range. I verified that Beamforming, MU-MIMO, and Fast Roaming were all on, and same speed. After some unsuccessful scrounging around the net, i decided to turn off IPV6 which was previously successfully set to "Auto Detect". After the config change, i ran another test, and low and behold:
Those speedtests are now in the 700-850 range on Wifi. Is this just my experience or is this a known issue?

[FURRYe38]

What wireless device are you using for wireless speed testing?

@Christian_R

[Mrgoodall]

 Model Name: iMac

  Processor Name: Intel Core i7

  Processor Speed: 4 GHz

  Number of Processors: 1

  Total Number of Cores: 4

  L2 Cache (per Core): 256 KB

  L3 Cache: 8 MB

  Memory: 32 GB

and iphone 8Plus

[FURRYe38]

Does your ISP support IPv6 natively? If not, you can keep IPv6 disabled...

[Mrgoodall]

iphone 8p

iMac 

[Mrgoodall]

yes

[FURRYe38]

Interesting find. I would presume it's not an issue if it helps wireless speeds.