

jjmb

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Re: [IPv6] Comcast IPv6 Address Assignment/Delegation



We assign an IPv6 address (/128) and a delegated prefix to routers that support IPv6 and are enabled. By default, today, if your router does not offer a hint that it can support more than one IPv6 VLAN (see RFC3633) we by default will delegated a /64. However, for routers that can support more than one VLAN or a shorter than /64 prefix we will today offer up to a /60.



We will be changing the defaults later this year so that /60 is the default. I will post updates on my Comcast blog when we launch these updates. (»



For residential broadband we currently do not offer the ability to manage the reverse zone for the delegated prefix nor do I foresee this anytime soon. Most if need or are interested in this are commercial customers, as such we will be offering the ability to manage PTR records for our commercial DOCSIS services.



As I am sure you would agree native is far more superior than tunneled IPv6. We analyzed this closely and chose native IPv6 over tunneled (6rd) as performance and predictability were much better. Further, most tunneled deployments of IPv6 have plans to re-deploy IPv6 natively.



HTH,



John Jason Brzozowski I run the IPv6 program at Comcast and can answer your questions.We assign an IPv6 address (/128) and a delegated prefix to routers that support IPv6 and are enabled. By default, today, if your router does not offer a hint that it can support more than one IPv6 VLAN (see RFC3633) we by default will delegated a /64. However, for routers that can support more than one VLAN or a shorter than /64 prefix we will today offer up to a /60.We will be changing the defaults later this year so that /60 is the default. I will post updates on my Comcast blog when we launch these updates. (» blog.comcast.com/author/ ··· ozowski/ For residential broadband we currently do not offer the ability to manage the reverse zone for the delegated prefix nor do I foresee this anytime soon. Most if need or are interested in this are commercial customers, as such we will be offering the ability to manage PTR records for our commercial DOCSIS services.As I am sure you would agree native is far more superior than tunneled IPv6. We analyzed this closely and chose native IPv6 over tunneled (6rd) as performance and predictability were much better. Further, most tunneled deployments of IPv6 have plans to re-deploy IPv6 natively.HTH,John Jason Brzozowski



Dan Austin

@phoenix.com Dan Austin Anon It is good to hear that the plan is for a /60 allocation. I've been waiting for the static business plans to receive IPv6 and hoping for a larger allocation since I need to use one subnet to connect

the mandated 'router' to my real router.



Of course that plan still falls apart if the CPE does not let me add static routes to put one or more /64 subnets downstream.

derekivey

join:2006-03-30

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Any updates on when the IPv6 trials for the Business Class customers will start? I emailed NetDog back in December and he put us down on the list.



MikeBalt

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I'm trying to retrieve a /60 via DHCP-PD, but when I set my SLA-Len to 4 I'm receiving a /64. If I try any other value I just don't learn a prefix. Any ideas?...



EG

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Union, NJ EG Premium Member said by MikeBalt : I'm trying to retrieve a /60 via DHCP-PD, but when I set my SLA-Len to 4 I'm receiving a /64. If I try any other value I just don't learn a prefix. Any ideas?...

That's what they currently supply to the LAN. A /64.



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NetFixer Premium Member said by graysonf: They will supply /60 to LAN on routers that will take it. See:



»Re: [IPv6] Comcast IPv6 Address Assignment/Delegation





When I was running my DIR655 with its IPv6 firewall disabled, I got a /60 network assignment:









After I enabled the IPv6 firewall, I now get a /64 assignment (and a different WAN IPv6 address, and a different LAN PD prefix):









Enabling the IPv6 firewall is the only thing that changed on my side. The rest of the DIR655's IPv6 setup is the same, and the firmware is the same. Fortunately, I don't need (and wasn't depending on) the /60 assignment; but if I had been using it, I would have been pissed that something as simple (and normal) as enabling the IPv6 firewall would cause such a major change in my IPv6 addressing. After I enabled the IPv6 firewall, I now get a /64 assignment (and a different WAN IPv6 address, and a different LAN PD prefix): And it appears to be a coin toss whether or not Comcast (and/or the router) decides if your router will take it.When I was running my DIR655 with its IPv6 firewall disabled, I got a /60 network assignment:



NetDog

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Parker, CO NetDog to derekivey

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said by derekivey: Any updates on when the IPv6 trials for the Business Class customers will start? I emailed NetDog back in December and he put us down on the list.

Soon.. Hate to say working on it.. But working on it..Soon..

NetDog NetDog to EG

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said by EG: said by graysonf: They will supply /60 to LAN on routers that will take it. See:



»Re: [IPv6] Comcast IPv6 Address Assignment/Delegation



Apparantly that is quite current and not what I learned from Comcast Tuska recently. EG.. I pinged you on this one.. If you request anything smaller then a /64 you could have issues..

NetDog NetDog to NetFixer

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said by NetFixer: said by graysonf: They will supply /60 to LAN on routers that will take it. See:



»Re: [IPv6] Comcast IPv6 Address Assignment/Delegation



Enabling the IPv6 firewall is the only thing that changed on my side. The rest of the DIR655's IPv6 setup is the same, and the firmware is the same. Fortunately, I don't need (and wasn't depending on) the /60 assignment; but if I had been using it, I would have been pissed that something as simple (and normal) as enabling the IPv6 firewall would cause such a major change in my IPv6 addressing.



My home router is a 3845, I have 5 LAN's off of it so yes I would request a /61 so I can enabled all my LAN's for native IPv6.



So the next question is why would I ask for a /60 (16 networks) when I don't need a /60 but a /61 (8 networks). This is just me but I would only ask for that I need..



/60 (16 Network)

/61 (8 Network)

/62 (4 Network)

/63 (2 Network)

/64 (1 Network) This is not a Comcast issue but a router issue, if your router doesn't support more then one LAN or network behind the WAN why would you need more then one /64?My home router is a 3845, I have 5 LAN's off of it so yes I would request a /61 so I can enabled all my LAN's for native IPv6.So the next question is why would I ask for a /60 (16 networks) when I don't need a /60 but a /61 (8 networks). This is just me but I would only ask for that I need../60 (16 Network)/61 (8 Network)/62 (4 Network)/63 (2 Network)/64 (1 Network)



EG

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said by NetDog: EG.. I pinged you on this one.. If you request anything smaller then a /64 you could have issues..

Got it. Thank you sir !



camper

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said by jjmb: I run the IPv6 program at Comcast and can answer your questions.... [a bunch of excellent info snipped]



jjmb, many thanks for your informative answer. jjmb, many thanks for your informative answer.



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said by NetDog: said by NetFixer: said by graysonf: They will supply /60 to LAN on routers that will take it. See:



»Re: [IPv6] Comcast IPv6 Address Assignment/Delegation



Enabling the IPv6 firewall is the only thing that changed on my side. The rest of the DIR655's IPv6 setup is the same, and the firmware is the same. Fortunately, I don't need (and wasn't depending on) the /60 assignment; but if I had been using it, I would have been pissed that something as simple (and normal) as enabling the IPv6 firewall would cause such a major change in my IPv6 addressing.



My home router is a 3845, I have 5 LAN's off of it so yes I would request a /61 so I can enabled all my LAN's for native IPv6.



So the next question is why would I ask for a /60 (16 networks) when I don't need a /60 but a /61 (8 networks). This is just me but I would only ask for that I need..



/60 (16 Network)

/61 (8 Network)

/62 (4 Network)

/63 (2 Network)

/64 (1 Network)

This is not a Comcast issue but a router issue, if your router doesn't support more then one LAN or network behind the WAN why would you need more then one /64?My home router is a 3845, I have 5 LAN's off of it so yes I would request a /61 so I can enabled all my LAN's for native IPv6.So the next question is why would I ask for a /60 (16 networks) when I don't need a /60 but a /61 (8 networks). This is just me but I would only ask for that I need../60 (16 Network)/61 (8 Network)/62 (4 Network)/63 (2 Network)/64 (1 Network)



Comcast definitely used to supply the requested /60, but that suddenly stopped, and that is illustrated in the screen shots I previously posted. It is perhaps a total coincidence, but it happened after /60 vs /64 allocations were initially discussed in this forum in which I posted that I was getting a /60 assignment.



I had initially thought that perhaps enabling the IPv6 firewall in the router had caused this change, but I have since temporarily disabled the IPv6 firewall and rebooted the router, but I still only got the /64.



FWIW, "I" wasn't explicitly requesting a /60 allocation, the router was just getting it by default (I only have the option to enable/disable DHCP-PD). I don't currently need it (since I have a business class "c05" config file, my guest network can have its own totally isolated IPv4 and /64 IPv6 network), but I just thought that it was interesting that I used to automatically get the /60 allocation, but suddenly that stopped (for no reason that is apparent to me). It would seem to me to be a Comcast issue when the router does support multiple IPv6 networks (I previously tested with my guest network behind it), and it used to get the /60 allocation but now it does not get it.Comcast definitely used to supply the requested /60, but that suddenly stopped, and that is illustrated in the screen shots I previously posted. It is perhaps a total coincidence, but it happened after /60 vs /64 allocations were initially discussed in this forum in which I posted that I was getting a /60 assignment.I had initially thought that perhaps enabling the IPv6 firewall in the router had caused this change, but I have since temporarily disabled the IPv6 firewall and rebooted the router, but I still only got the /64.FWIW,wasn't explicitly requesting a /60 allocation, the router was just getting it by default (I only have the option to enable/disable DHCP-PD). I don't currently need it (since I have a business class "c05" config file, my guest network can have its own totally isolated IPv4 and /64 IPv6 network), but I just thought that it was interesting that I used to automatically get the /60 allocation, but suddenly that stopped (for no reason that is apparent to me).



NetDog

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Parker, CO NetDog Premium Member said by NetFixer: It would seem to me to be a Comcast issue when the router does support multiple IPv6 networks (I previously tested with my guest network behind it), and it used to get the /60 allocation but now it does not get it.



Comcast definitely used to supply the requested /60, but that suddenly stopped, and that is illustrated in the screen shots I previously posted. It is perhaps a total coincidence, but it happened after /60 vs /64 allocations were initially discussed in this forum in which I posted that I was getting a /60 assignment.





But we are accepting anything up to a /60 via DHCP, but the route injection will not work on some CMTS's. I have tested this and I am using it so I know this works and doesn't work in some cases.



My config looks like this:



on My WAN

ipv6 dhcp client pd hint ::/61

ipv6 dhcp client pd prefix-from-Comcast



On my LAN's

ipv6 address prefix-from-Comcast ::1/64



ipv6 address prefix-from-Comcast ::1:0:0:0:1/64



ipv6 address prefix-from-Comcast ::2:0:0:0:1/64



and so on... I PMed you my work email, send me your info like the DUID of your router and cable modem MAC..But we are accepting anything up to a /60 via DHCP, but the route injection will not work on some CMTS's. I have tested this and I am using it so I know this works and doesn't work in some cases.My config looks like this:on My WANipv6 dhcp client pd hint ::/61ipv6 dhcp client pd prefix-from-ComcastOn my LAN'sipv6 address prefix-from-Comcast ::1/64ipv6 address prefix-from-Comcast ::1:0:0:0:1/64ipv6 address prefix-from-Comcast ::2:0:0:0:1/64and so on...

MrJester

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said by jjmb: We will be changing the defaults later this year so that /60 is the default. I am very glad you are considering the future and not sticking users with a single /64. From an academic perspective, can you share the rationale behind choosing a /60 instead of /56?

biomesh

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join:2006-07-08

Tomball, TX 1 recommendation biomesh Premium Member Probably due to the fact that very few people can or will use a /60 effectively.



I doubt there are any business class customers that could use 256 /64s vs the 16 with a /60.



I am guessing as time goes on, this may change and larger allocations may be made available.



Mike Wolf

join:2009-05-24

Beachwood, NJ Mike Wolf Member What allocation is it for 1 address (a router with dhcp)



NetFixer

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NetFixer Premium Member said by Mike Wolf: What allocation is it for 1 address (a router with dhcp)











After Comcast finishes upgrading their CMTS software, you may (or may not) be able to get a network /60 assignment for a PD prefix starting with "2601" as illustrated below with a snapshot of my DIR655 IPv6 status taken before Comcast temporarily rolled back giving out /60 assignments.





After Comcast finishes upgrading their CMTS software, you may (or may not) be able to get a network /60 assignment for a PD prefix starting with "2601" as illustrated below with a snapshot of my DIR655 IPv6 status taken before Comcast temporarily rolled back giving out /60 assignments. A router's WAN should receive a /128 with a prefix beginning with "2001:558". A router's LAN should receive a /64 with the PD prefix beginning with "2601". If your router is capable of supporting multiple IPv6 networks on its LAN, you will currently also receive a network /64 assignment with a PD prefix beginning with "2601". The image below (from my DIR655) illustrates this.



Mike Wolf

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Beachwood, NJ Mike Wolf Member This is all I see on my router regarding IPv6 so I don't even know if it can support /128 or /60 or something.



NetFixer

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NetFixer Premium Member said by Mike Wolf: This is all I see on my router regarding IPv6 so I don't even know if it can support /128 or /60 or something.





Your screen shot also clearly shows that you are getting the current maximum /64 assignment on the router's LAN. There is really no way to tell if your router can support a /60 network assignment until Comcast once again starts issuing the /60 assignments. However, it you did not previously (before last week) get a /60 network assignment, then your router probably doesn't support it. The fact that your router does not report the assignment size for its WAN interface pretty much implies that it is properly getting a /128 (which is the size for a single IP address, and that is all a router's WAN needs).Your screen shot also clearly shows that you are getting the current maximum /64 assignment on the router's LAN. There is really no way to tell if your router can support a /60 network assignment until Comcast once again starts issuing the /60 assignments. However, it you did not previously (before last week) get a /60 network assignment, then your router probably doesn't support it.



Mike Wolf

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Beachwood, NJ Mike Wolf Member Honestly I've never fully understood how IPv6 works, I'd love to learn but till I'm in the mood for my head to explode I'm comfortable just happy "It works" lol

I'd love to find a router that fully supports all of what IPv6 offers, I mean on all my systems there's no IPv6 DHCP lease information and no IPv6 DHCP settings on the router side.



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NetFixer Premium Member said by Mike Wolf: Honestly I've never fully understood how IPv6 works, I'd love to learn but till I'm in the mood for my head to explode I'm comfortable just happy "It works" lol

I'd love to find a router that fully supports all of what IPv6 offers, I mean on all my systems there's no IPv6 DHCP lease information and no IPv6 DHCP settings on the router side.





And FWIW, there is a reason that I picked both of the IPv6 routers that I use from When you do get in the mood, there are some basic tutorial links at Comcast's IPv6 Information Center to get you started. Until then, there is no point in worrying about whether your router supports multiple IPv6 networks on its LAN side because you would not be ready to implement it. Also, if you are using recent versions of Windows, OS X, or a recent *nix distribution, IPv6 on the client side should indeed work automatically.And FWIW, there is a reason that I picked both of the IPv6 routers that I use from Comcast's approved/tested list . IPv6 has a way of making everyone's head explode.