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Comment by flyinghamster | Hacker News Reader

I've tried to run IPv6 on my Comcast connection. Unsurprisingly, Comcast doesn't get the point of IPv6. They allocate one single IPv6 address to my router. That's right, ONE. LOUSY. ADDRESS.

This seems to be a "feature" of owning your own modem rather than renting one of theirs. I hesitate to even try to get this fixed via their tech support.

I guess if I want IPv6 connectivity, I'm either going to have to get a tunnel from Hurricane Electric (SIXXS is shutting down), or carve out some IPv6 space from my Linode and tunnel it to my home network.

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Actually, Comcast supports DHCP prefix delegation (I'm led to believe everywhere, but it works at my home anyway), which is pretty much the Right Thing in this space. Your default DHCPv6 request is from a single client and it returns a single IP, as expected. And you can then do NAT across that if you want, which is what their default routers do.

But if you want a subnet, you can make a second DHCPv6 request with prefix delegation metadata, and the server will establish a route for a full /64 subnet to your existing IP and return it to you. Then you can hand these out however you want (though they won't give you bigger than a /64 so you can do internal subnet routing).

The only annoyance is that none of the existing Linux distros support this yet as part of their network client integration, so you have to script it yourself around dhclient (see the -P argument), which is a little hairy if you want to get the hooks right (I punted and just did it once manually and left dhclient running).

>The only annoyance is that none of the existing Linux distros support this yet as part of their network client integration, so you have to script it yourself around dhclient (see the -P argument), which is a little hairy if you want to get the hooks right (I punted and just did it once manually and left dhclient running).

I think OpenWRT has all you need for this. At least I think that's exactly what I did with my ISP config on my own router just with the LuCi web interface.

Yep, same with Cox in my area. I'm running Sophos UTM Home which supports prefix delegation, I'm sure there are others that are plug and play as well.

Comcast will give out up to a /60 for residential if you hint for it in DHCPv6-PD.

UPDATE: I now have IPv6 connectivity via my shiny new EdgeRouter POE. Now I just have to poke a few holes in the firewall where appropriate (now that I've set drop-by-default rules).

Getting it to work with the ER-POE was non-intuitive but not as bad as I was expecting. I'm even getting a /60...

Linux doesn't support it? My Comcast router has a /64 given to it by Comcast and all my linux boxes connected to it work like a charm.. although I haven't been able to get my dd-wrt router to pass them on yet.

Linux supports it just fine, you have to do the integration on your own. If you want to use the distro-provided DHCP setup, you need to work out the NetworkManager hooks on your own to add the PD client at the right spots.

I suspect most people don't use a Linux box as their router (with the obvious exception of router distros and embedded Linux on routers).

Most people will read this, I think, and think a Linux client won't accept a V6 from a router that has obtained it's delegation via DHCP-PD..

That doesn't sound correct. Are you absolutely sure you aren't also getting a prefix delegation thru DHCPv6? That's currently the common way to provide IPv6 connectivity currently for residential users.

From what I remember hearing, Comcast was giving /60s thru PD.

No, I don't get a prefix. No /60, no /64, not even a /120, just one single address. A /128. Maybe I should jump on their forums and raise a fuss. I'm not at all confident that calling tech support would get me to someone who even had a clue what IPv6 is.

Just to be sure, with a routed network being aimed at your house, you'll actually receive two subnets (well, a single address in one subnet, and a whole second subnet). You need to use DHCP-PD or similar to make use of it.

The /128 sounds perfectly normal, and is used as a "point to point" link between the ISP and your modem. Over this, DHCP prefix delegation typically gives you a whole second subnet of /60 or so. If your modem isn't handling DHCP-PD, then all your see is 1 measly address even though they've likely allocated and pushed 295,147,905,179,352,825,856 addresses to you.

Hmmm, maybe I should revisit this. I first tried it a year or so ago with pfSense on a virtual machine. Between the IPv6 issues and generally poor performance (long story), I went back to my IPv4-only configuration with DD-WRT on a D-Link DIR-825.

I'm now using a Ubiquiti EdgeRouter POE, and maybe I should give it another shot. I'm not convinced I'll actually get a prefix from Comcast, though.

It may differ by region, but in the SF Bay Area I've been getting a /60 from Comcast residential for a few years now using a MikroTik router. See here: http://i.imgur.com/2mrRk01.png

The edge router can do DHCP-PD, but it needs some configuration for it to do it, there's lots of info on the Ubuiquiti forums about it. Good luck!

Comcast has a decent ipv6 technology group (by necessity - they were an early adopter/innovator of carrier-grade v6 as they have more CPE to address than can be fit into 10/8). If you ever become interested in resolving this you may want to dig through http://www.comcast6.net and see if you can find a direct contact to work with.

I don't have any contacts myself, I'm just a customer and interested observer.

FTR, I don't get a prefix from them, either.

I tunnel all traffic through Comcast via a VPN, though, because I consider them a hostile network, so I don't especially care.

I can confirm that, my home network is currently routing a /60 from Comcast.

Not necessarily your situation -- but I noticed this from Time Warner as well and it turned out to be my old Airport Extreme hardware. Even with the latest firmware it wouldn't receive the delegated range. As soon as I upgraded to the latest model, it properly received a delegated range from TWC without me doing anything else. Just saying, there is a lot of reason to hate cable companies, but it's not always their fault :)

That's surprising, in Denver Comcast gives my Time Capsule a /64 (and has for years, we were one of the earlier areas to get v6 service from them). Doubly surprising since the v6 RFCs all but forbid giving out less than a /64, and Comcast is a leader rather than follower of v6 technology. I wonder if the modem manufacturer is at fault instead.

I regularly ssh straight into to my suspended WoL Macbook over v6, and never went out of my way to set up a single bit of it. A half dozen new technologies working perfectly out of the box!

"carve out some IPv6 space from my Linode and tunnel it to my home network."

I'm planning on doing exactly this using openvpn as my transport (because I already have an extensive ipv4 openvpn system). Has anyone tried it? I'm not interested so much in how to do it, which I think I know, but in anecdotes along the lines of "it makes openvpn crash" or "linode told me I was being abusive and cut me off" or whatever.

I've had ipv6 for decades I guess. I even got one of the Hurricane Electric "sage" tee shirts last decade. But when sixxs goes down I lose ipv6 connectivity for the first time since the DSL days at the turn of the century.

I tunnel all of my traffic through my Linode. I had to disable ipv6, because I was getting constant captcha checks from facebook, cloudflare, and google. No matter how many different ipv6 addresses I tried, traffic is always marked as suspicious. As soon as I disabled ipv6, everything went smoothly.

This sounds like CloudFlare etc have just blacklisted hosting provider IPv6 blocks, as there a real easy way to get millions of "clean" IPs priced by the hour.

CloudFlare etc certainly dont do this with SiXXS IPv6 addresses, or any traditional residential provider I'm aware of.

Well, I'd love to use ipv6. In fact, I can't wait. But, what am I supposed to do?

  * T-mobile: ipv4  
  * Office: ipv4  
  * Verizon: ipv4  
  * University: ipv4
  * Linode: ipv6 (but flagged as hostile)

Google will not just show me captchas, but will deactivate accounts if I use some of their apis. I had to reverify several accounts when I've tried using ipv6.

I'm not being backward about ipv4, I'm really not. But we're in denial about the fact that we still live in an ipv4 world. And I don't like seeing the last vestiges of non-profit ipv4 address space being liquidated.

T-Mobile stopped handing out IPv4 addresses to handsets on iOS 10 -- IPv6 Only.

Yeah, T-Mo is IPv6 on smartphones such as Android/iPhone.

I route all of my mobile traffic through an older Android device that only connects to their 3G network. Maybe that's why...

You should be able to get a /56 or /60 from them using DHCPV6-PD.

I have Comcast and get a range. It may be a regional thing or your setup is just wonky.

Granted, I have business class so that I don't violate their ToS by hosting stuff and to get a dedicated IP.

Rogers in Canada gives /64, which is lovely.

My old ISP gave me a /64 and it was anything but lovely. It's too small to break up into subnets, and they were unable to give anything larger.

This caused me to switch ISP's and now I have a static /48. That's much nicer.

I get a /60 from Comcast in Chicago.

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