Some do this... but, RFC3021 is just a RFC - please correct me if I'm wrong, but, I don't think it is in any official specification.
I found that the cheaper the router, the better the support! Whilst using some routers going back a few years (Juniper and Sonicwall especially) we kept having error upon error - Juniper just didn't work, and Sonicwall wouldn't accept it as a static IP but would allow it via DHCP, however, zone based firewalls failed and the counters were not working/it couldn't tell which was inbound and which was outbound along with other random annoying errors. In addition, a lot of the leading IPAM tools failed, so, any sort of management at scale was a pain. If you want a bit of a mind***k, take a look at /32 subnets! That's one that really feels like it shouldn't work, but, it does - A few years ago, we basically had a slightly modified DHCPD installation (I think it now works on a standard branch) which if you set up many DHCP pools with /32 ranges, it would issue fine. Again, I found the cheaper the device, the better the support but don't ask me how this worked! The above /32 was recently talked about on Reddit if anyone is interested here - https://www.reddit.com/r/networking/comments/f2fu8e/using_32_host_routes_to_conserve_ipv4_addresses/ William William HilsumEZPC Limited Managing Director M: +44 7828252201 E: [email protected] W: https://ezpcltd.com 2 Cross Way Petts Wood Kent BR5 1PF, UK EZPC Ltd is a company registered in England and Wales under number 4781783 with VAT Registration GB820559632. Registered office: 2 Cross Way, Petts Wood, Kent, BR5 1PF, United Kingdom. The information in this message is confidential and is intended for the use of the addressee only. -----Original Message----- From: uknof <[email protected]> On Behalf Of Benny Lyne Amorsen Sent: 20 February 2020 12:32 To: [email protected] Subject: Re: [uknof] why aren't we giving /31 to customers On Thursday 2nd of February 2020, Tom Bird wrote: > Morning, > > Given the RFC for this is something like 20 years old now, but I still > see /30s being used by just about everyone, is there still a good > reason for this? There are at least three major reasons that $EMPLOYER has not embraced /30 for customers. One is that CE support is sketchy. E.g. you can configure a /31 on a RouterBoard and it will simply fail to work. Instead you have to do it the pre-RFC way with a /32. This works for basic connectivity and some routing protocols work as well. If it breaks you get to keep both pieces. Another is that user education is lacking. Give a customer a /31 and they will invariably be on the phone asking how to configure it. Looking up how to configure yet another random brand CE is not a productive use of support resources. The last one is that with /30 you can use DHCP to hand out the single CE address. I have no idea whether DHCP supports /31, but I am confident that even if it does, most CEs will not handle it correctly. If a customer asks for a /31 specifically they can certainly have it. When they ask, they generally (alas, not always) know whether their CE does it correctly. Personally I would much rather see widespread support for 4rd (RFC7600) in CEs than support for /31. Or really, any other 4-over-6 standard, as long as almost every CE supports it. /Benny
