Comcast Rolling Out Home Gateway Support for IPv6 – And Nothing's Controversial About a /64…

Outstanding news for Comcast subscribers last week at the North American IPv6 Summit! Comcast’s John Brzozowski, chief architect for IPv6 and distinguished engineer, indicated that Comcast was now moving its IPv6 support from just supporting single computers to supporting entire home networks. In a Network World article titled “Comcast is first U.S. ISP to offer IPv6 to home gateway users“, Carolyn Duffy Marson reports on Brzozowski’s comments, including the fact that the service is already available in two cities.

This step is critical for adoption of IPv6 by home users as most home users do typically have some type of home gateway providing Internet access to the many devices within their home.  Prior to this step, you could only connect a single computer for IPv6 access.  While this certainly made sense for Comcast as they started testing out their production IPv6 support, it is great to see them moving on to support the home gateway use case that the majority of Comcast customers will have.

Comcast also very helpfully is providing a website showing which home gateway devices will work with IPv6 (look for checkmarks in the IPv6 column):

My only real issue with the article is this sentence:

In a somewhat controversial move, Comcast is giving each of its home networking users what’s called a /64 block of IPv6 addresses, which represents more than 18 quintillion IPv6 addresses…

There’s actually nothing “controversial” about providing a /64 block as that’s the standard allocation of IPv6 addresses to a router.  This enables all devices within the router’s network to use “Stateless Address Autoconfiguration (SLAAC)” to automatically create their IPv6 addresses by combining the “router advertisement” with the devices own MAC address.   It’s what makes IPv6 “just work” for devices.

However, I completely understand why the author would write that.  When I first started digging into the details of IPv6 several years back I had the same reaction – aren’t we setting ourselves up for failure by starting out already giving up half our address space to the host portion?

Coming from the address-constrained IPv4 space – and just with an engineer’s view of efficiency, it seemed insanely wasteful!  And in some cases where there are always going to be a limited number of devices on a network, it certainly may be wasteful… but for the majority of networks using a /64 enables SLAAC and also makes room for innovation.  As we look at the sensor-based “Internet of Things”, we may find use for that very large address space.  Time will tell, but in the meantime the /64 allocation is just how things are done in IPv6 – welcome to the world of IP address abundance!

Aside from that minor note, it was great to see this article and congrats to Comcast for rolling out this support for IPv6 home gateways!  As World IPv6 Launch nears, this will definitely enable more people to get connected!


3 replies on “Comcast Rolling Out Home Gateway Support for IPv6 – And Nothing's Controversial About a /64…”


Thank you for commenting and yes, I’m aware of the desire for multiple subnets and the allocation of shorter prefixes. The way I read the article this morning it did sound to me like the author was surprised that this many addresses were being given out and hence my text here.

As I just re-read the article right now (twice, in fact), it doesn’t sound that way to me any more. So either Network World edited the article since I read it (which I doubt)… or more likely I didn’t have sufficient caffeine in my system when I wrote this post. I’ll note that a couple of people left comments to the article itself along the same line as what I wrote.

Anyway, thanks for taking the time to post a reply and take me to task on this. I appreciate it!


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