Throttled download speeds on new router with Comcast (ipv6 vs ipv4)

Question

Issue with Comcast cable on Linksys or Cisco routers (and others) involving throttled download speed on ipv4.

I recently upgraded my internet service to 100+ Mbs and also upgraded my router to gigabit and AC. Problem is the clients with wireless N only get substandard speed.

Prior to upgrade, all clients got around 55 Mb/s down and 11 Mb/s up. Now:

• Wired client: 125 Mbs down / 25 Mbs up
• HTC One (AC): 80-90 Mbs down / 25 Mbs up - 433 Mbs link speed
• Nexus 7 (Wireless N only): 18 Mbs down/ 24 Mbs up - 65 Mbs link speed
• Ubuntu Laptop (Wireless N only): 24 Mbs / 21 Mbs up - 150 Mbs link speed

So I've actually given two of my devices a downgrade.

It's a Linksys EA6350 router.

I've tried disabling 5 Ghz band, disabling firewall, setting 2.4 Ghz to 'Wireless N only', changing channels on 2.4 Ghz band and generally fiddling with every setting imaginable.

The only thing that seemed to help was enabling the 'Media Prioritization' in the router and giving the laptop 27 Mbs down speed, still less than it started with.

Anything try to daisy chain my old router to the new one and connect N clients on that? Not ideal solution.

EDIT: Interestingly, when I went to the Xfinity speed test site (rather than the well known one by Ookla), I get two different speed test results on the the throttled laptop, one for ipv6 and one for ipv4. The problem is the speeds I am seeing when downloading files from various sites is throttled.

If I disable ipv6 in the router settings I only get the slow speeds on the laptop.

Answer 1

This is actually an issue with Comcast on certain Linksys or Cisco routers. Comcast's network is ill-configured and marks all the packets as low priority. More information can be found at Comcast help forums.

The easy solution is to disable WMM. In my router this was in 'Media Prioritization', 'Settings'. With this option disabled I am able to get full download speeds on IPv4 on laptop.

However disabling WMM makes it impossible for some devices to connect in Wireless N, so this is not optimal solution.

I am just going to return the router and get one that is not Linksys or Cisco.

EDIT The same problem exists with a Netgear R6250 router. I had to disable WMM and also select "Enable QoS" (after removing all the priority rules) in settings for the same fix.

With this router I am able to connect all the clients, with laptop getting 150 Mb/s link speed and 100+ Mbs download speeds on ipv4 and ipv6, and Nexus 7 falling back to Wireless G (I think) with 54 Mb/s link speed.