4 ms·
On the ISP side, you get a ton of space. As a consumer on residential broadband, you get a limited amount of space. I have a /40 and assign down to a /127 for P
by jabart 2y ago
On the ISP side, you get a ton of space. As a consumer on residential broadband, you get a limited amount of space. I have a /40 and assign down to a /127 for Point to Point links in a datacenter. IPv6 is still an older standard and a lot of assumptions were built in about a /64 being the smallest subnet. Some routers didn't support a /127 for PtP until recently even though it was an RFC in 2010. I think even NAT66 was discouraged until everyone realized you cann't have a dual-wan setup with two different prefix delegations or everything breaks when one wan goes down and everyone has to get a new DHCP address.
- zamadatix 2y agoGoing smaller than /64 often has hardware consequences beyond just assumptions from old RFCs. E.g. in most all of Broadcom's line of ASICs you can do /127s but doing so requires initializing the ASIC on boot in a way that it has a decent chunk less table space because the IPv6 entries all have to be 128 bits now instead of just 64 bits. Many vendors expose this as a config item but default it to off kind of like the non-standard "allow routes more specific than a local subnet" option. On the software side of lower end gear it can depend on how exactly they implemented the dataplane. NAT66 (or just NPTv6 in this scenario) is still discouraged today even though sometimes it's easier to just throw hands in the air for dual-wan setups like that. Some still have hopes of a rosy multipath client future but honestly if you know you aren't going to be able to use your own PA space or connecting your SD-WAN to a CDN/Cloud to do the same isn't viable for the use case then it's definitely an "eh, yeah not a great setup but not the end of the world" kind of solution just as bad as the remaining options at this point.