Skip to main content
madbrain76's profile
madbrain76
Rousing Reactor
Expressive Exchange
Conversation Starter

Contributor

 • 

101 Messages

Thursday, November 6th, 2025 12:15 AM

IPv6 broken on Windows clients with pfSense and XB8

I have an XB8 gateway in bridge mode. I have been using pfSense for many years as my router. IPv6 used to work fine for all my clients.

IPv6 stopped working on my Windows clients recently. It still works on Linux clients. I believe the difference is due to Windows clients using Prefix delegation, and Linux clients using SLAAC. The prefix delegation likely isn't working with pfSense.

If I bypass pfSense, and switch the XB8 to router mode, IPv6 works for all clients. This leads me to think that there is some setting in pfSense+ that's needed to make IPv6 work. I already reached out to pfSense community, but was unable to resolve this. The thread is at https://forum.netgate.com/topic/199213/comcast-ipv6-working-on-linux-clients-but-not-windows-clients .

Is anyone else using pfSense and IPv6 successfully ? And if so, with which settings ?

I tried to paste an image, but it failed, so here is a text paste instead of the DHCP6 client options for the WAN interface to which the XB8 is connected.

Use advanced DHCPv6 configuration options.
Override the configuration from this file.
The value in this field is the delegated prefix length provided by the DHCPv6 server. Normally specified by the ISP.

For the LAN interface, I'm using "Track interface" as the IPv6 configuration type.

Any help would be appreciated.

Question

 • 

Updated 

23 days ago

20

1

0

Oldest First
Selected Oldest First
XfinityJeniece

Official Employee

 • 

3.6K Messages

23 days ago

Hey there, @madbrain76, thanks for reaching out through Xfinity Forums regarding your connection. How long have you had your pfSense router? I know you mentioned you reached out to their community. Did you reach out to their tech support for information?

2

0

madbrain76

Contributor

 • 

101 Messages

@XfinityJeniece​ I have had it several years. Unfortunately, there is no tech support available except for paid licenses. I'm using a free license.

It appears the issue is related to the size of my network. I have about 350 clients, including about 300 Wifi clients. If I disconnect the Wifi clients, the IPv6 is resolved on the Windows hosts, which are wired.

I don't see the IPv6 problem when using the XB8 as router, even with all 350 clients connected. It appears to be a problem on the pfSense side, either some configuration issue, or a bug.

Like

Reply

23 days ago

0

XfinityJustinM

Official Employee

 • 

404 Messages

@madbrain76, quite the mystery it seems! We will leave this post open for the community to chip in, but I find a lot of our more tech-savvy folk also frequent r/Comcast_Xfinity. It may be a good idea to create a discussion post here to gain some additional insight!

If you figure things out please come back to let us know what worked. 👍

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

Like

Reply

23 days ago

0

forum icon

New to the Community?

Start Here