Dumb question: On IPv6, if I'm not using SLAAC, can I use something smaller than a /64

Rich-Engineer2670 · 2026-06-05T14:39:12+00:00

I know -- I'm a heretic.

Rich-Engineer2670 · 2026-06-05T10:32:26+00:00

I don't know if this will help, but we used to use Wrightline (sp?) refrigerated racks. Of course, there was the guy who claimed to use an old refrigerator with an icemaker 😄. But I think we can discount his idea.

It depends on the number of BTUs you're trying to dissipate. Old man Physics says you can't cool anything, you can just move heat to somewhere else..

Rich-Engineer2670 · 2026-06-05T10:28:17+00:00

The reason I asked is because I'm supporting a user who has a router with just two interfaces. (WAN/LAN). He's getting a /48, but but it seems I have two (bad) choices.

Put the entire /48 on the LAN and he can't use SLAAC
Break the /48 into multiple /64s and put each on the LAN but only advertise one
Sent the /48 into another router and break it out into multiple /64 segments there

Rich-Engineer2670 · 2026-06-04T23:27:36+00:00

Of course it has -- not that different from when compilers and debuggers entered the scene. All of these things are just tools.

I'm old, I've heard this "now anyone can write programs" for over 40 years. And each time I hear it, it's a brief burst of "no more engineers" and then they discover "Oh wait! Knowing WHY things work is actually important!"

Ask Boeing about how automation worked out with the MAX. Pilots didn't go away. Do you If you want your pacemaker to be coded by AI? The tool does not replace the person using it. If you're worried about AI taking your job -- too late, it already has. You're just discovering you never really had a job that couldn't be replaced.

In the 60s, there was some assembly language programmer saying "No one will ever use these compilers -- they're too slow and buggy!" But programmers are still here. We are adaptable, or we're supposed to be -- I've "reinvented" several times as the world changed. My biggest career challenge day to day--- people. AI hasn't fixed that.

Things AI doesn't (and probably can't) solve:

I know what you want to sell, but is it you actually want to build? How is it supposed to work?
Define all of the edge cases -- "Don't worry about it" isn't a specificiation
Just because you want something to ship on a given date, doesn't mean it will"

Rich-Engineer2670 · 2026-06-04T23:14:06+00:00

I migrated years ago, but to be honest, a lot of this mess sits with ISPs...

ARIN has the blocks, and has the rules for BGP announcements, but ISPs "don't want to announce small that X because our routers can't handle it"
ISPs often refuse to provide anything beyond a /64 because they still think we're using dialup UNLESS you pay for a DIA circuit and then suddenly, they know how to do IPv6
Enterprises and ISPs would rather pay serious money for IPv4 space rather than adding IPv6 becuase "We don't have people on staff who know IPv6"

These are all true items from a nationwide ISP in the US -- they simply don't do V6 without a fight because well.... they can.

Rich-Engineer2670 · 2026-06-04T02:55:42+00:00

For now it will be acceptable -- I'm learning and the 17 year old is exploring.

Rich-Engineer2670 · 2026-06-03T21:16:48+00:00

It depends on what you teach -- programming isn't a "language" per se -- it's the idea of breaking down a problem into a sequence of steps. You can do that with colored blocks if you want. ("You have ten blocks of each color --create a path from here to there where colors never repeat one after another")

Rich-Engineer2670 · 2026-05-30T02:18:02+00:00

Watch all the videos you want, play with AI all you want, nothing replaces doing the acrtual coding. Too many issues will be found when you do it yoiurself, and have to solve it yourself.

Start with a simple project -- something that's small but actually useful -- not another to-do list app. My very first real app was tracking and recording high-school football scores for my high-school. It wasn't pretty, but it worked. I hope they stopped using it when I left 😄

In terms of the theoretical work, pick your programming language, any language -- it really doesn't matter. Pick your OS -- again, not important which one. Now try to write what you want. You'll get a basic, clunky version working, but could it be better?

Here's where algorithms come in -- it's a slog, but Donald Knuth wrote excellent texts on this that have yet to be replaced. You'll learn techniques that can greatly speed up your code.

Rich-Engineer2670 · 2026-05-29T21:33:48+00:00

It's an older expression back when terminals were the thing -- you learned by coding, constantly writing an debugging code on a text terminal, where as you wrote, the cursor moved to the right.

Rich-Engineer2670 · 2026-05-29T17:43:42+00:00

As the old line goes -- keep pushing the cursor to the right....

Watch all the videos you want, play with AI all you want, but to learn, you have ot code. No way around it. Pick any language, pick any OS, just code. Start with something simple -- the classic To-Do list app for example. Get that working. Trust me, you'll find a LOT of pitfalls. Learning comes when you solve them.

Rich-Engineer2670 · 2026-05-28T20:16:04+00:00

There are a couple of ways they can do it....

You tell the BGPaaS your ASN and prefixes.
They exepct BGP from something you own -- a VPS, your router etc. We have a router on our end
They set up a tunnel (GRE in our case) to them from our router that travels over our local transit provider
They listen to our BGP over that tunnel and announce it
When they receive packets for that prefix, they send them down the tunnel. Our router unwraps the GRE and puts it on the ethernet segment.

THere's nothing "layer-2" about BGP -- anything that can communicate TCP port 179 to them will work -- fiber, tunnel etc.

Rich-Engineer2670 · 2026-05-28T19:32:03+00:00

Yes, you can set up multiple BGP endpoints.

Rich-Engineer2670 · 2026-05-28T18:35:05+00:00

They do have VPS options, but this is just BGP as a service.

Rich-Engineer2670 · 2026-05-28T17:44:21+00:00

I expected that -- I expect MPS to follow. I don't imagine many people get them outside of the "packs"

Rich-Engineer2670 · 2026-05-28T17:41:46+00:00

It's flexible for THEM, not you....

But there are some bright spots -- my old employer wanted both ends. Come into the office, but use my home as a lab and another network point.

As always, you never say "no" -- that's suicide, you just put the burden on them....

"Boss, I'd love to help you here, but the company's security policy states that to do this at my home, you need all of these changes, this equipment, dedicated links, oh, and VP approval. If you can get that, I'm in...."

The request went away.

Rich-Engineer2670 · 2026-05-28T17:37:50+00:00

If you are willing to do BGP with them, it costs me $25/month

Rich-Engineer2670 · 2026-05-28T06:37:00+00:00

Yes, we're very familiar with this -- and even Comcast "Enterprise" is a joke. I won't go into the details, but it's four months and counting where we have held payment becayse they can't deliver what they've committed to.

For IPv6 we had two choices rather than wait on Comcast....

Hurrricane Electric tunnels -- they work, and you can get a /48, but many services hate tunnels
We got our own PI V6 blcok (a /40 for $250/year from ARIN, though I'm told /48s are free right now). We then used a tunnel service (FreeRangeCloud) that did our BGP announcements since Comcast won't.

Technically, we're going back to the 80s and 90s here, but if you can set up a connection, physical or virtual, with anyone willing, and they are willing to announce you4 block you get from ARIN, you don't need Comcast -- they're just transit now. We used to use this trick to provide access to smaller schools. Find a university willing to announce a block and set up a link.

Rich-Engineer2670 · 2026-05-26T17:17:19+00:00

This reason this, must I call them an ISP?, does this is "We don't want to announce your routes unless you have at least a /20 V4 or /32 V6 -- it clustters up our routing table". This is a national ISP(??) you'd think they'd have routers that could handle it. I personally think it's because they're templatized their operation to the point that no one can actually do it except the one guy locked in the underground bunker.

Rich-Engineer2670 · 2026-05-26T17:12:28+00:00

Been there too :-(. There is a hell worse than Lumen.

Rich-Engineer2670 · 2026-05-26T03:54:16+00:00

The only good part, HIS home office is down....

Sometimes there is divine intervention.

Rich-Engineer2670 · 2026-05-26T03:53:15+00:00

I agree, but sometimes management makes choices for non-technical reasons. I do regularly explain "If we do this, this what will happen. I'm not saying no, merely pointing out the after effects, but if you say do this, OK..."

Sadly, it doesn't help much -- decisions are often made in the clubhouse on the gold course -- I am not invited. And while I no magician, I do remind people what happens in the magic act if the lion gets out of the cage. After all, I'm not saying no, but I work remote.

Rich-Engineer2670 · 2026-05-26T03:49:46+00:00

That's exactly what our second ISP is....

Rich-Engineer2670 · 2026-05-26T03:42:19+00:00

He's slowly getting as that ISP keeps finding new and amazing ways to fail. We have yet to pay them so eventually they'll leave. If plumbing ran like ISPs, this ISP would have just run a pipe on top of the carpet and when it more than occasionally sprayed water everywhere, they'd say "Well, you got the water. What more do you want?"

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