IPv6 Setup with Comcast/Xfinity

[Keenan]

Be advised using IPv6 in passthrough is a bad idea. Passthrough does just that it passes right through with no active firewall so your v6 connections are wide open to the world. Be careful.

Yes, I set it back to Native. I'm now trying to figure out why I'm not getting any IPv6 connectivity. I'm with Comcast as well.

 

[geobernd]

Yes, I set it back to Native. I'm now trying to figure out why I'm not getting any IPv6 connectivity. I'm with Comcast as well.

I had this problem initially. Rebooting the Modem after the Router has already rebooted with IPV6 settings Native enabled fixed the issue and it has been working for me ever since (using a DPC3941B)

 

[Keenan]

I had this problem initially. Rebooting the Modem after the Router has already rebooted with IPV6 settings Native enabled fixed the issue and it has been working for me ever since (using a DPC3941B)

Just tried that and it made no difference, still no connectivity. I suspect the issue is with the Comcast gateway device but I'm not sure what exactly what to look for.

The below image is what my IPv6 page looks like.

 

[appleseed]

Comcast gateway

what's your gateway device, and is it in bridge mode ?

 

[JohnD5000]

It will make more sense when you look at each device individually, by going to each devices' Internet/DHCP settings, and see how they change depending on router settings above.

Where do you go to see this?

 

[Keenan]

what's your gateway device, and is it in bridge mode ?

It's a Technicolor CGM4140COM. The belwo link is to the FCC data sheet for it. It's a Comcast rental gateway which I've been using as it allows me to get unlimited data for $40 instead of the $50 per month when using my own modem. That $10 is looking more and more like a very weak reason to use their equipment.

https://fccid.io/G95CGM414X/User-Manual/User-Manual-3423718

And yes, it's in bridge mode.

 

[appleseed]

Where do you go to see this?

For example, to see DHCP settings on a laptop/PC/tablet running Windows/Linux/OS X:

Windows (10): https://support.microsoft.com/en-us/help/15089/windows-change-tcp-ip-settings
Linux: (gnome) https://help.gnome.org/users/gnome-help/stable/net-manual.html.en
OS X: https://support.apple.com/guide/mac-help/use-dhcp-or-a-manual-ip-address-on-mac-mchlp2718/mac

 

[appleseed]

It's a Technicolor CGM4140COM.
And yes, it's in bridge mode.

You should be able to log in and see if you are pulling an ipv6 address:

• Click on the Connection tab at the left of the screen

Look for WAN IP Address (IPv6). If you don't see one then a restart should fix it.
Comcast is probably now above 95% complete with residential ipv6.

 

[Keenan]

You should be able to log in and see if you are pulling an ipv6 address:

• Click on the Connection tab at the left of the screen

Look for WAN IP Address (IPv6). If you don't see one then a restart should fix it.
Comcast is probably now above 95% complete with residential ipv6.

It does show an address there but I've restarted the modem a few times and those IPv6 test pages indicate no connection.

 

[appleseed]

on the router, try changing ipv6 Connection type to Disable then to Native
may or may not need a restart in between

 

[appleseed]

IPv6 test pages indicate no connection.

are you running anything out of the ordinary on the router, (scripting like AMTM, VPN, FreshJr, PieHole, DNSCrypt, etc), or just basic home networking?

 

[Keenan]

on the router, try changing ipv6 Connection type to Disable then to Native
may or may not need a restart in between

Still nothing. The Comcast modem sees the address but for some reason, the router doesn't.

 

[appleseed]

If you're not running other things like scripts, I think your 86U needs a downgrade (or upgrade depending on what you're on). IPV6 should be working natively on the 86U, both Merlin and Asus default firmware.

Only other thing to consider is free space on both your RAM and Flash. Sometimes when you connect a device like a drive, or add a number of devices to a static list, the router can behave wonky (technical term) as you approach RAM/Flash limits. Other times it's just a bad install that a reinstall should fix.

 

[EmeraldDeer]

I noticed your from Mass. Where is Cloudfare data center? I'm also from Mass and currently using Quad9. Wondering if should switch to CF? Thanks

The Cloudflare data center is in Boston.

Should you switch from Quad9? Cloudflare does not do security filtering while Quad9 does. I am relying upon Diversion to do DNS filtering. Several months ago I was testing DNS over TLS with Quad9, CleanBrowsing and Cloudflare. Quad9 and CleanBrowsing were not reliable. At the time I was a paying customer of CleanBrowsing and had opened tickets, but to no avail.

By the way, I am also using Cloudflare for NTP via "pool time.cloudflare.com"

 

[EmeraldDeer]

Try running the commands below. The issue which required these commands had been addressed, but I am not sure at which version.

echo "1" > /proc/sys/net/ipv6/conf/all/accept_ra
echo "1" > /proc/sys/net/ipv6/conf/all/forwarding
echo "1" > /proc/sys/net/ipv6/conf/eth0/accept_ra
echo "0" > /proc/sys/net/ipv6/conf/eth0/forwarding

If this were to work it would be immediate. You would see the values populate on the IPv6 tab in System Log.

 

[Keenan]

If you're not running other things like scripts, I think your 86U needs a downgrade (or upgrade depending on what you're on). IPV6 should be working natively on the 86U, both Merlin and Asus default firmware.

Only other thing to consider is free space on both your RAM and Flash. Sometimes when you connect a device like a drive, or add a number of devices to a static list, the router can behave wonky (technical term) as you approach RAM/Flash limits. Other times it's just a bad install that a reinstall should fix.

I downgraded to 384.14 and it made no difference.

 

[EmeraldDeer]

So Enable Router Advertisement advertises routers IP & DNS to my network, not outside network? If I have "Connect to DNS server automatically" to disable and set up Quad9, wouldn't Quad9 be set to locale cache anyhow? So, setting Router Advertisement to enable or disable would be the same thing? Or am I just really not getting what this setting does?

Yes, Router Advertisement assists IPv6 addressing on the LAN, not on the WAN. It is for SLAAC, which works differently from DHCP which is used for assigning addresses in IPv4.

The DNS server settings you are referring to are just that, they are not settings related to the router's caching DNS server/forwarder.

 

[appleseed]

I downgraded to 384.14 and it made no difference.

what happens when you try EmeraldDeer's suggestion - no change ?

 

[EmeraldDeer]

Still nothing. The Comcast modem sees the address but for some reason, the router doesn't.

I am not sure this will be applicable to your location but for Comcast here:
LAN IPv6 addresses begin with 2601
WAN IPv6 address begins with 2001
WAN IPv6 gateway address begins with fe80

If your WAN IPv6 address begins with 2601, then perhaps bridge mode is not working.

 

[Keenan]

I am not sure this will be applicable to your location but for Comcast here:
LAN IPv6 addresses begin with 2601
WAN IPv6 address begins with 2001
WAN IPv6 gateway address begins with fe80

If your WAN IPv6 address begins with 2601, then perhaps bridge mode is not working.

All those match what I'm seeing in the modem connection menu.