Posted: Mon Oct 03, 2016 17:21 Post subject: IPv6 on Comcast
Hey! I'm pretty sure this isn't really an "Advanced Networking" questions, but I couldn't find a a better matching board.
I'm trying to get an IPv6 connection on my home network and I couldn't find a solution for days. Here is what I got so far:
When I plug my MacBook directly into the modem I get a IPv6 IP and connection and everything seems to work just fine (test-ipv6 is happy).
When I plug in my old AirPort Express it thinks it gets a IPv6 connection, but the values don't seem to be right: Default Gateway is sometimes ::1. Sometimes I get an IP and gateway that look like they could make sense, but my IPv6 connections always time out. When I enable an 6to4 tunnel on the APE it will seem to work but coonections seem to fail kind of randomly when I try to rely on a IPv6 connection.
On my dd-wrt router I tried IPv6 with PRefix Delegation, I tried Dhcp6s, I tried Radvd. I wouldn't get an IPv6 address in any of these configurations.
Comcast will take a variety of prefixes. The default PD is 64; the Macbook is probably getting a 128-bit NA rather than a PD. Try these settings in DD-WRT's Setup->IPv6 tab to get a working configuration:
DHCPv6 with Prefix Delegation
Prefix length 64
On the Setup->Basic tab, if you checkmarked Use DNSmasq for DHCP, you may need to setup the IPv6 address ranges. In my Services tab under Additional DNSmasq options, I tell DNSmasq where to get the IPv6 ranges:
The PD is tied to the WAN MAC, and Comcast has 7-day PD leases. To change my PD to 60 for subnetting, I had to change the prefix length to 60 and clone the MAC off an old router. Alternatively I could have changed the prefix and switched off IPv6 for a week. _________________ [Broadcom] Asus rt-ac66u r35531 ('66 should only be factory reset through the DD UI)
Fix RT-AC66U "wl1 [2.4 GHz TurboQAM]". DD-WRT failsafe UI @ http|https://169.254.255.1/
Just wanted to say thank you, been trying to figure out how to get ipv6 working for a while now on comcast and i followed this advice. I didnt have to change any advanced options just the stuff under setup --> ipv6 once i changed that i checked on ipv6test.com and its all green now.