Re: Using /126 for IPv6 router links
On Sat, 23 Jan 2010 20:55:52 -0600 Brandon Galbraith brandon.galbra...@gmail.com wrote: Sometimes good enough perfect Never know what is going to come along to turn your addressing plan on its head. It seems to me that what this really is about is trying to be in the best position in the future. I think mainly it's about trying to avoid unexpected and future renumbering/change of prefix length costs. Possible positions or situations are : 1. you use a variety of node address lengths across your network, and there are no future consequences - everything works and continues to work 2. you use a single node address length (i.e. /64) across your network, and there are no future consequences - everything works and continues to work 3. you use a variety of node address lengths, and you'll have to renumber to /64s, because you encounter unacceptable issues e.g. device performance issues, inability to use features you'd find useful e.g. SEND. 4. you use a single node address length, and you'll have to move to variable length node addresses, because the IPv6 address space ends up not being as big as it was designed and calculated to be. Ideally, situations one 1. or 2. will occur, as they're the least costly. 1. is both initially and operationally slightly more costly than 2. as you'll also have to also accurately manage prefix lengths, and consider and/or address other non-/64 issues identified in RFC3627, which I think makes 2. the better choice. The question is, which of those two has the least risk of devolving into the corresponding 3. or 4? As the addressing architecture documents for IPv6 currently state that for other than addresses that start with binary 000, the interface ID are required to be 64 bits in length, it seems to me that situation 2. is the least risky and least likely to devolve into situation 4. Vendors/developers using RFCs as authoritative IPV6 documents are going to assume /64s, as are future protocol developers. -brandon On 1/23/10, Larry Sheldon larryshel...@cox.net wrote: On 1/23/2010 8:24 PM, Owen DeLong wrote: On Jan 23, 2010, at 4:52 AM, Mathias Seiler wrote: In reference to the discussion about /31 for router links, I d'like to know what is your experience with IPv6 in this regard. I use a /126 if possible but have also configured one /64 just for the link between two routers. This works great but when I think that I'm wasting 2^64 - 2 addresses here it feels plain wrong. So what do you think? Good? Bad? Ugly? /127 ? ;) Use the /64... It's OK... IPv6 was designed with that in mind. 64 bits is enough networks that if each network was an almond MM, you would be able to fill all of the great lakes with MMs before you ran out of /64s. Did somebody once say something like that about Class C addresses? -- Government big enough to supply everything you need is big enough to take everything you have. Remember: The Ark was built by amateurs, the Titanic by professionals. Requiescas in pace o email Ex turpi causa non oritur actio Eppure si rinfresca ICBM Targeting Information: http://tinyurl.com/4sqczs http://tinyurl.com/7tp8ml -- Brandon Galbraith Mobile: 630.400.6992 FNAL: 630.840.2141
Re: Using /126 for IPv6 router links
That's why we have the safety valve... 2000::/3 is the total address space being issued currently. So, if we discover that there aren't enough /64s like we currently think there are, then, before we start issuing from 4000::/3, we can have a new address plan for that address space while leaving the 2000::/3 in it's current state of 1, or, ideally, 2. Owen On Jan 23, 2010, at 7:06 PM, Mark Smith wrote: On Sat, 23 Jan 2010 20:55:52 -0600 Brandon Galbraith brandon.galbra...@gmail.com wrote: Sometimes good enough perfect Never know what is going to come along to turn your addressing plan on its head. It seems to me that what this really is about is trying to be in the best position in the future. I think mainly it's about trying to avoid unexpected and future renumbering/change of prefix length costs. Possible positions or situations are : 1. you use a variety of node address lengths across your network, and there are no future consequences - everything works and continues to work 2. you use a single node address length (i.e. /64) across your network, and there are no future consequences - everything works and continues to work 3. you use a variety of node address lengths, and you'll have to renumber to /64s, because you encounter unacceptable issues e.g. device performance issues, inability to use features you'd find useful e.g. SEND. 4. you use a single node address length, and you'll have to move to variable length node addresses, because the IPv6 address space ends up not being as big as it was designed and calculated to be. Ideally, situations one 1. or 2. will occur, as they're the least costly. 1. is both initially and operationally slightly more costly than 2. as you'll also have to also accurately manage prefix lengths, and consider and/or address other non-/64 issues identified in RFC3627, which I think makes 2. the better choice. The question is, which of those two has the least risk of devolving into the corresponding 3. or 4? As the addressing architecture documents for IPv6 currently state that for other than addresses that start with binary 000, the interface ID are required to be 64 bits in length, it seems to me that situation 2. is the least risky and least likely to devolve into situation 4. Vendors/developers using RFCs as authoritative IPV6 documents are going to assume /64s, as are future protocol developers. -brandon On 1/23/10, Larry Sheldon larryshel...@cox.net wrote: On 1/23/2010 8:24 PM, Owen DeLong wrote: On Jan 23, 2010, at 4:52 AM, Mathias Seiler wrote: In reference to the discussion about /31 for router links, I d'like to know what is your experience with IPv6 in this regard. I use a /126 if possible but have also configured one /64 just for the link between two routers. This works great but when I think that I'm wasting 2^64 - 2 addresses here it feels plain wrong. So what do you think? Good? Bad? Ugly? /127 ? ;) Use the /64... It's OK... IPv6 was designed with that in mind. 64 bits is enough networks that if each network was an almond MM, you would be able to fill all of the great lakes with MMs before you ran out of /64s. Did somebody once say something like that about Class C addresses? -- Government big enough to supply everything you need is big enough to take everything you have. Remember: The Ark was built by amateurs, the Titanic by professionals. Requiescas in pace o email Ex turpi causa non oritur actio Eppure si rinfresca ICBM Targeting Information: http://tinyurl.com/4sqczs http://tinyurl.com/7tp8ml -- Brandon Galbraith Mobile: 630.400.6992 FNAL: 630.840.2141
Re: Using /126 for IPv6 router links
On 1/23/2010 9:47 PM, Owen DeLong wrote: 64 bits is enough networks that if each network was an almond MM, you would be able to fill all of the great lakes with MMs before you ran out of /64s. Did somebody once say something like that about Class C addresses? The number of /24s in all of IPv4 would only cover 70 yards of a football field (in a single layer of MMs). Compared to the filling the three-dimensional full volume of all 5 great lakes, I am hoping you can see the vast difference in the comparison. Of course--I was asking about the metaphorical message implying More than we can imagine ever needing. I remember a day when 18 was the largest number of computers that would ever be needed. -- Government big enough to supply everything you need is big enough to take everything you have. Remember: The Ark was built by amateurs, the Titanic by professionals. Requiescas in pace o email Ex turpi causa non oritur actio Eppure si rinfresca ICBM Targeting Information: http://tinyurl.com/4sqczs http://tinyurl.com/7tp8ml
Re: Using /126 for IPv6 router links
In a message written on Sat, Jan 23, 2010 at 01:52:21PM +0100, Mathias Seiler wrote: I use a /126 if possible but have also configured one /64 just for the link between two routers. This works great but when I think that I'm wasting 2^64 - 2 addresses here it feels plain wrong. So what do you think? Good? Bad? Ugly? /127 ? ;) I have used /126's, /127's, and others, based on peers preference. I personally have a fondness for /112's, as it gives you more than 2 addresses, and a DNS bit boundary. For all the pontification about how there are enough /64's to number all the grains of sand, or other nonsense, I think that ignores too much operational information. rDNS is important, and becomes harder in IPv6. Making it easier is importnat. Having a scan of a /64 fill your P2P T1 is poor design, all because you assigned 2^64 addresses to a link that will never have more than 2 functional devices. Most importantly, we should not let any vendor code any of these into software or silicon, in case we need to change later. -- Leo Bicknell - bickn...@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/ pgpmW9UnydIXo.pgp Description: PGP signature
