Comcast filtering SMTP (TCP 25) for IPv6, but 587 still works!

Noticed this weekend that I couldn’t respond to emails on my personal hosted domains. I thought at first first they changed my PD prefix, but it was up to date in Postfix. Tried submission port and it worked just fine. So looks like Comcast finally caught up with “feature parity” in disallowing outbound SMTP connections on TCP 25.

IPv6 speedtest comparison since moving to DOCSIS 3.x

Last time I ran any kind of flash/java based speedtest was back in Feb. when I was still on my tunnel and behind a DOCSIS 2.x modem:

Decided that I needed to re-run the test now that I’m both behind a DOCSIS 3.x modem, and have native IPv6 from Comcast:

Comcast residential IPv6 works without a hiccup

With all my servers and services IPv6 enabled remotely, it was time to check out how well Comcast is doing with their residential IPv6 rollout. First thing I did was check out their listed compatible DOCSIS 3.x modems that had IPv6 support. Saw the Motorola SB6120 listed, and having used their ISDN products in mid-90s, figured it would be a good investment. Hunted around and found that the nearby Fry’s Electronics had the SB6121. Picked it up for $100. They also had Zoom modems that stated they supported IPv6. But after dealing with their Rockwell chipset modems in the early 90s, I’ll pass.

Got home, swapped out the old RCA rental from Comcast, and plugged in the new one. Called them up, got them the HFC MAC and had them provision it. Took them a bit to do, but finally my laptop was getting a Comcast IP, and that was a good start. Plugged in the D-Link DIR-825, it got its old IP back (since its MAC hadn’t changed). Went into the IPv6 WAN Configuration, and initially picked “Autoconfiguration (SLAAC/DHCPv6)”, but decided that since we live in the FUTURE, I’d let the D-Link try “Auto” and sort it out. Well it worked, and I had IPv6 on the D-Link’s WAN interface, and my laptop was autoconfiguring out of Comcast space.

But there was one last hurdle: Comcast. While IPs had configured fine, I couldn’t reach anywhere. I spent roughly 30 minutes reviewing all configuration settings, making sure I had routes, and rebooting everything a few times to no avail. Finally gave in, called back Comcast, and the tech was like “oh, let me disable the firewall on our side.” POOF! Everything worked. So Comcast residential IPv6 is definitely live in my area, and just needed a new shiny DOCSIS 3.x modem.

AT&T Residential IPv6 access

One of the ISP participants in WorldIPv6Launch day is AT&T. They are working towards a goal of having at least 1% of their wired residential customers have IPv6 connectivity. A recent post on the NANOG mailing list states that they have started this with 6rd.

6rd was first launched into production by a residential ISP in France, Free.fr. Comcast was also looking at 6rd for their deployment as part of their trials. Their 6rd trial ended June 2011, and they have since decided that they will deploy native dual-stack to their customers.

Similar to 6to4, 6rd can work for getting your users connectivity, but does require the CPE or directly connected computers to understand and be compatible with 6rd. Another issue would be overloaded relays or what happens when one goes down. Users of 6to4 see this frequently, however with 6to4 it can be a bit more the troubleshoot which relay is having the issue. With 6rd it should be more obvious, and thus quicker to address since the relay is only operated on the residential ISP’s network.