Re: IPv6 Default Allocation - What size allocation for Loopback Address
Hi, On Sun, Oct 12, 2014 at 02:53:36PM +0200, Sander Steffann wrote: Hi, Op 11 okt. 2014, om 23:00 heeft Roland Dobbins rdobb...@arbor.net het volgende geschreven: On Oct 11, 2014, at 2:09 PM, Tim Raphael raphael.timo...@gmail.com wrote: From my research, various authorities have recommended that a single /64 be allocated to router loopbacks with /128s assigned on interfaces. Yes, this is what I advocate for loopbacks. I often use the first /64 for loopbacks. I'm not a big fan of using all-zero third or fourth quarters of $PREFIX at all (at least not if one follows RFC 5952 uses static, short IIDs, which will be case for loopbacks). On a crowded visio diagram it might not be easy to spot that 2001:db8::1, 2001:db8:0:1::1, 2001:db8:1::1 and 2001:db8:1:1::1 are all different addresses, potentially on the same hierarchy level. Hence we prefer to use or just FF at some point within the prefix for loopbacks, e.g. 2001:db8:FF::1 etc. best Enno Loopbacks are often used for management, iBGP etc and having short and easy to read addresses can be helpful. Something like 2001:db8::1 is easier to remember and type correctly than e.g. 2001:db8:18ba:ff42::1 :) Cheers, Sander -- Enno Rey ERNW GmbH - Carl-Bosch-Str. 4 - 69115 Heidelberg - www.ernw.de Tel. +49 6221 480390 - Fax 6221 419008 - Cell +49 173 6745902 Handelsregister Mannheim: HRB 337135 Geschaeftsfuehrer: Enno Rey === Blog: www.insinuator.net || Conference: www.troopers.de Twitter: @Enno_Insinuator ===
Re: IPv6 Default Allocation - What size allocation for Loopback Address
Hi, Op 11 okt. 2014, om 23:00 heeft Roland Dobbins rdobb...@arbor.net het volgende geschreven: On Oct 11, 2014, at 2:09 PM, Tim Raphael raphael.timo...@gmail.com wrote: From my research, various authorities have recommended that a single /64 be allocated to router loopbacks with /128s assigned on interfaces. Yes, this is what I advocate for loopbacks. I often use the first /64 for loopbacks. Loopbacks are often used for management, iBGP etc and having short and easy to read addresses can be helpful. Something like 2001:db8::1 is easier to remember and type correctly than e.g. 2001:db8:18ba:ff42::1 :) Cheers, Sander
Re: IPv6 Default Allocation - What size allocation for Loopback Address
- On Oct 12, 2014, at 8:53 AM, Sander Steffann san...@steffann.nl wrote: Hi, Op 11 okt. 2014, om 23:00 heeft Roland Dobbins rdobb...@arbor.net het volgende geschreven: On Oct 11, 2014, at 2:09 PM, Tim Raphael raphael.timo...@gmail.com wrote: From my research, various authorities have recommended that a single /64 be allocated to router loopbacks with /128s assigned on interfaces. Yes, this is what I advocate for loopbacks. I often use the first /64 for loopbacks. Loopbacks are often used for management, iBGP etc and having short and easy to read addresses can be helpful. Something like 2001:db8::1 is easier to remember and type correctly than e.g. 2001:db8:18ba:ff42::1 :) Cheers, Sander I concur. I think think some have gotten confused with the suggesting of allocating a /64 for *ALL* loopbacks versus allocating a full /64 per loopback. Loopbacks should be /128, but all loopbacks for a site should be within a single /64 (the first one for reasons others, including Sander have said. -Randy
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On Sat, Oct 11, 2014 at 1:41 AM, Faisal Imtiaz fai...@snappytelecom.net wrote: A follow up question on this topic.. For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? (the BCOP document suggests this, but does not offer any explanation or merits of one over the other). Hi Faisal, One of the viewpoints held by some in the IETF is that an IPv6 address is not 128 bits. Rather, it is 64 bits of network space and 64 bits of host space. I'm told this viewpoint is responsible for the existence of a 128 bit address instead of IPv6 using 64 bit addresses. If you follow that reasoning, the subnet mask should always be /64, no matter where the address is assigned. There are, of course, excellent operational reasons not to religiously follow that plan. Regards, Bill Herrin -- William Herrin her...@dirtside.com b...@herrin.us Owner, Dirtside Systems . Web: http://www.dirtside.com/ May I solve your unusual networking challenges?
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On 10/12/14 3:00 PM, William Herrin wrote: On Sat, Oct 11, 2014 at 1:41 AM, Faisal Imtiaz fai...@snappytelecom.net wrote: A follow up question on this topic.. For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? (the BCOP document suggests this, but does not offer any explanation or merits of one over the other). Hi Faisal, One of the viewpoints held by some in the IETF is that an IPv6 address is not 128 bits. Rather, it is 64 bits of network space and 64 bits of host space. I'm told this viewpoint is responsible for the existence of a 128 bit address instead of IPv6 using 64 bit addresses. If you follow that reasoning, the subnet mask should always be /64, no matter where the address is assigned. https://tools.ietf.org/html/rfc6164 Is a standards track document. it is imho a repudiation of the assumptions about the dimensions of the host field. There are, of course, excellent operational reasons not to religiously follow that plan. Regards, Bill Herrin signature.asc Description: OpenPGP digital signature
Re: IPv6 Default Allocation - What size allocation for Loopback Address
In message CAP-guGXezFUSSpDznCtb6DZNXpV=2rbdwgh+sf-xsdkj_mc...@mail.gmail.com, William Herrin writes: On Sat, Oct 11, 2014 at 1:41 AM, Faisal Imtiaz fai...@snappytelecom.net wrote: A follow up question on this topic.. For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? (the BCOP document suggests this, but does not offer any explanation or merits of one over the other). Hi Faisal, One of the viewpoints held by some in the IETF is that an IPv6 address is not 128 bits. Rather, it is 64 bits of network space and 64 bits of host space. I'm told this viewpoint is responsible for the existence of a 128 bit address instead of IPv6 using 64 bit addresses. IPNG looked at 48 bits, 64 bits and 128 bits addresses. 48 and 64 bits would both have left everyone tightly managing subnet sizes and allocation sizes like we do in IPv4. IPv6 went to 128 bits to *allow* for a 64/64 split eventually where one didn't have to tightly manage subnet sizes and allocations. Earlier plans looked at 48 bits for the subnet size based in Ethernet MAC. It went to 64 bits with 48 bit MAC's padded to 64 bits to account for 64 bit MAC's and because a 64/64 split would possibly be more efficient / simpler. No one was making it a hard split at the time. If you follow that reasoning, the subnet mask should always be /64, no matter where the address is assigned. There are, of course, excellent operational reasons not to religiously follow that plan. Regards, Bill Herrin -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On Oct 11, 2014, at 12:41 PM, Faisal Imtiaz fai...@snappytelecom.net wrote: For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? In the BCOP, this is noted so that those who suboptimally address their p-t-p links with /64s can be consistently suboptimal by doing the same with their loopbacks, so that *all* their interfaces are sinkholes. But the BCOP also talks about /128s. -- Roland Dobbins rdobb...@arbor.net // http://www.arbornetworks.com Equo ne credite, Teucri. -- Laocoön
Re: IPv6 Default Allocation - What size allocation for Loopback Address
Subject: Re: IPv6 Default Allocation - What size allocation for Loopback Address Date: Sat, Oct 11, 2014 at 05:41:43AM + Quoting Faisal Imtiaz (fai...@snappytelecom.net): A follow up question on this topic.. For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? (the BCOP document suggests this, but does not offer any explanation or merits of one over the other). I use a /128 -- these addresses are going to be used de-aggregated in the IGP only; outside they are part of your aggregated allocation. Then again; I'm using /127 on links. Just because it is a tad easier to do dual-stack on the scripts that build the config. And, I get to have all my links in 2001:0db8:f00:feed:dada::/80 :-) -- Måns Nilsson primary/secondary/besserwisser/machina MN-1334-RIPE +46 705 989668 I'm thinking about DIGITAL READ-OUT systems and computer-generated IMAGE FORMATIONS ... signature.asc Description: Digital signature
Re: IPv6 Default Allocation - What size allocation for Loopback Address
In the BCOP, this is noted so that those who suboptimally address their p-t-p links with /64s can be consistently suboptimal by doing the same with their loopbacks, I am trying to understand what is sub-optimal about doing so...Waste of Ipv6 space ? or some other technical reason ? (is a /64 address are a 'sinkhole' the only reason ? ) Regards Faisal Imtiaz Snappy Internet Telecom - Original Message - From: Roland Dobbins rdobb...@arbor.net To: nanog@nanog.org list nanog@nanog.org Sent: Saturday, October 11, 2014 2:00:21 AM Subject: Re: IPv6 Default Allocation - What size allocation for Loopback Address On Oct 11, 2014, at 12:41 PM, Faisal Imtiaz fai...@snappytelecom.net wrote: For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? In the BCOP, this is noted so that those who suboptimally address their p-t-p links with /64s can be consistently suboptimal by doing the same with their loopbacks, so that *all* their interfaces are sinkholes. But the BCOP also talks about /128s. -- Roland Dobbins rdobb...@arbor.net // http://www.arbornetworks.com Equo ne credite, Teucri. -- Laocoön
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On Oct 11, 2014, at 1:33 PM, Faisal Imtiaz fai...@snappytelecom.net wrote: I am trying to understand what is sub-optimal about doing so...Waste of Ipv6 space ? or some other technical reason ? It's wasteful of address space, but more importantly, it turns your router into a sinkole. (is a /64 address are a 'sinkhole' the only reason ? ) That's a pretty big reason not to use /64s. -- Roland Dobbins rdobb...@arbor.net // http://www.arbornetworks.com Equo ne credite, Teucri. -- Laocoön
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On 10/11/2014 8:41 AM, Faisal Imtiaz wrote: For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? The number of IPs addresses used on them subnets on them loopbacks is as far as I can foresee only one [for each loopback]. So a subnet of size one address should do it. And that seems to be the same in v4 and v6 Frank
Re: IPv6 Default Allocation - What size allocation for Loopback Address
From my research, various authorities have recommended that a single /64 be allocated to router loopbacks with /128s assigned on interfaces. This makes a lot of sense to me as (which has been said) there is no other *need* in the foreseeable future to have more than one IP on the loopback - this is the purpose of it. Any technology or design that requires this has got scaling issues and should not be used anyway. Regards, Tim Raphael On 11 Oct 2014, at 2:37 pm, Roland Dobbins rdobb...@arbor.net wrote: On Oct 11, 2014, at 1:33 PM, Faisal Imtiaz fai...@snappytelecom.net wrote: I am trying to understand what is sub-optimal about doing so...Waste of Ipv6 space ? or some other technical reason ? It's wasteful of address space, but more importantly, it turns your router into a sinkole. (is a /64 address are a 'sinkhole' the only reason ? ) That's a pretty big reason not to use /64s. -- Roland Dobbins rdobb...@arbor.net // http://www.arbornetworks.com Equo ne credite, Teucri. -- Laocoön
Re: IPv6 Default Allocation - What size allocation for Loopback Address
On Oct 11, 2014, at 2:09 PM, Tim Raphael raphael.timo...@gmail.com wrote: From my research, various authorities have recommended that a single /64 be allocated to router loopbacks with /128s assigned on interfaces. Yes, this is what I advocate for loopbacks. -- Roland Dobbins rdobb...@arbor.net // http://www.arbornetworks.com Equo ne credite, Teucri. -- Laocoön
Re: IPv6 Default Allocation - What size allocation for Loopback Address
A follow up question on this topic.. For Router Loopback Address what is wisdom in allocating a /64 vs /128 ? (the BCOP document suggests this, but does not offer any explanation or merits of one over the other). Regards. Faisal Imtiaz Snappy Internet Telecom
