[HN Gopher] Build your own Dial-up ISP with a Raspberry Pi
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Build your own Dial-up ISP with a Raspberry Pi
Author : arjunbajaj
Score : 89 points
Date : 2026-04-03 15:08 UTC (7 hours ago)
(HTM) web link (www.jeffgeerling.com)
(TXT) w3m dump (www.jeffgeerling.com)
| bigbuppo wrote:
| Don't need to do that. I use a USR Total Control chassis as a
| white noise generator.
| kotaKat wrote:
| I feel like it would have been more fun to build your own line
| simulator with a 9 volt battery and some old phone line and just
| skip the dialtone altogether for a little magic... the $120
| black-box telco simulator takes a lot of the fun out.
|
| But then again, based on Pi pricing today, the $120 telco
| simulator goes nicely with a $300 Pi 5.
| giantrobot wrote:
| Line simulators are fun. The ports can call each other and
| there's no need to set any custom init strings on the modem
| like you need with the 9 volt trick. For some old devices
| that's a necessity.
|
| You can also use an old VoIP ATA from Linksys/Cisco as a cheap
| line simulator. Like a fully analog TLS the ports can call each
| other. They can be a PITA to configure right but they're cheap
| and work well enough.
|
| I've used all three methods, the TLS is the easiest. An ATA can
| be useful if you've got more than one and your dial-in server
| is in a different room from the client you're playing with. An
| ATA can also be set to "call" another device. So your office
| ATA can call the basement ATA (with your Linux server) as an
| example.
| ssl-3 wrote:
| It's not particularly custom:
|
| Just issue ATX0D on one modem and ATA on the other. Bingo
| bango: One modem thinks it's initiating a call (without
| concern about the lack of dialtone), and the other thinks it
| is answering a call.
|
| But yeah, simulators are fun. A person I used to call "boss"
| used one with a dry pair of copper that ran all the way
| across town for his internet connection for a couple of
| years.
|
| (His shop had space that was used by a local dialup ISP for a
| POP. In exchange for the space and the electricity, his shop
| got free internet over a T1 in the days before we had DSL or
| DOCSIS. It was a great trade for both parties and I felt
| giddy downloading things at work at >1.5 Mbps instead of
| ~0.0336 Mbps.
|
| In an effort to save some money on a dedicated phone line and
| ISP bill at home, he ordered a cheap circuit from the phone
| company that they billed as an "alarm circuit" -- it was
| about $20 per month.
|
| One modem was his at house behaving mostly-normally along
| with the simulator, and another was at the shop connected to
| our all-singing, all-dancing 486DX4 Linux box. It was stable
| and cheap and somewhat ridiculous.)
| alnwlsn wrote:
| If you ever want more phone lines than that, you can pick up an
| old Cisco VG-224 from Ebay for less than half the price of that
| line simulator, and you get 24 lines. There is a configuration
| that will let you use it as a standalone unit where all the lines
| can call each other with custom phone numbers (here's some notes
| [1]).
|
| The main catch is that they have a 50-pin Centronics style
| connector on them which you will have to break out somehow to
| your RJ11s. Also, they are big (1U rack) and have fans.
|
| I've got a few of these and have been meaning to set them up with
| a bunch of modems and a bunch of computers, but haven't gotten to
| it yet. Modems do seem to work in the limited testing I've done.
| They do (as expected) work great with telephones, including pulse
| dialing.
|
| [1] https://alnwlsn.com/z/pots/cisco-vg224.html
| ssl-3 wrote:
| > The main catch is that they have a 50-pin Centronics style
| connector on them which you will have to break out somehow to
| your RJ11s.
|
| This is just another lost art (traditional phones are either
| dead or are instead IP) that I once learned a fair bit about:
|
| The name varies regionally (I've heard them called Centronics,
| cinch, and CHAMP; though around here, we call them Amphenols).
| The Easy Method is the same regardless of name: It centers
| around a split (aka "50 pair") 66 punch block[1] that is
| mounted to a wall, or to a wall-like object.
|
| Buy a pre-terminated 25-pair cable with the right connector on
| at least one end, and punch that down in order[2] on one side
| of the 66 block. That connects the system to the punch block.
| Importantly, those wires never get touched again.
|
| Phones (or more precisely, wires for jacks for phones) connect
| to the other side of the 66 block. Those wires also never get
| touched again.
|
| The two things (phones, systems) are connected/disconnected
| with bridge clips that combine the two halves of the block
| (which only allows 1:1 ordering, but that's often just fine).
|
| Alternatively, a "we fancy!" variation uses single-pair cross-
| connect wire so that arbitrary phones can quickly be connected
| to arbitrary system ports -- maybe on completely separate
| blocks.
|
| After that, plug in the Amphenol. Plug in the phones. Have fun
| talking to yourself.
|
| (Or, at least: That's an easy way for small stuff. Bigger stuff
| (hundreds or thousands of pairs) eventually really wants better
| organization, but punch blocks are still normally the order of
| the day there, too.)
|
| [1]: https://en.wikipedia.org/wiki/66_block
|
| [2]: https://news.ycombinator.com/item?id=41428998
| CursedSilicon wrote:
| Do the VG224's manage V.90/V.92 speeds? Jeff's setup falls into
| the usual trap other YouTubers do. Dialing a modem through an
| ATA or other device directly into another modem caps the speeds
| at V.34 (33600 baud)
|
| From what I understand of telecom of that era. You want to
| effectively keep as much of the signal digital as possible.
| With (ideally) the only "analog" part remaining being the link
| between the customer modem and the PBX.
|
| The VG224 being (effectively) 24 ATA's in a trenchcoat seems to
| meet that requirement. Though once installed you'd need to
| connect it to a PBX such as Asterisk. Then, as I understand it,
| "trunk" that as a T1 line into something that can digitally
| handle modem calls such as a Cisco AS5300.
| aimadetools wrote:
| I'd be curious if anyone has actually used a setup like this as a
| fallback for when their fiber goes down. The latency would be
| brutal, but a few kbps beats no bps
| connicpu wrote:
| It would be funny as a project but there's better low speed
| backup options like a starlink dish on standby mode (500kbps)
| elevation wrote:
| I pulled out a WRT54G the other day and set it to a 56K limit.
| A netbook running ubuntu(ish) took several days to complete an
| apt-get update. But when I connected my laptop with 50 browser
| tabs, the tabs themselves consumed 100% of the bandwidth with
| background traffic (despite my ad blocker) and no other network
| services worked at all.
|
| Unless you've tuned your system for it, dial-up modem speeds
| are functionally equivalent to "no connection at all".
| geerlingguy wrote:
| Timeouts are killer too... many modern apps assume slow or no
| response for more than 10 or 20 seconds is "Internet is down"
| and will stop trying.
|
| It's brutal, even with modern Internet, when people develop
| apps with the assumption of the Internet connection always
| having decent latency and bandwidth.
| dave78 wrote:
| Jeff mentioned in his video that just loading the front page of
| CNN would take something like an hour and a half (20+ MB).
|
| 33.6Kbps is not practical for much on the modern Internet in
| 2026. As mentioned in a sibling comment, Starlink (even in
| standby mode) would be much better. lite.cnn.com would load in
| about 10 seconds which is pretty good, but there's not much
| else like it left anymore.
|
| What's amazing is how great the Internet in the 1990s managed
| to be despite these limitations. Just like with RAM and disk
| space, developers back then had to be very mindful of bandwidth
| - today's devs (and agents) have the luxury of paying much less
| attention to that.
| j45 wrote:
| There are services which will remove all but the text when
| browsing and make it greatly lighter.
|
| 20+ mb is the weight of all the javascript javascripting,
| ultimately to arrange and display an html page.
| ssl-3 wrote:
| 20+ mb is also the weight of rendering the HTML inside each
| client, instead of at the server. It is the weight of
| continuous disdain for users, and of 30 years of not giving
| a fuck about adding yet another abstraction layer and
| making it someone else's problem.
| thesuitonym wrote:
| The way this is set up is using your normal fiber internet as
| the backbone, so if the fiber goes down, the dialup does, too.
| elevation wrote:
| What I would love to have is a few compact dialup-to-wifi bridges
| so I could wifi-ize 30 year old hardware.
|
| Would be neat to read email with an old POP client, or chat over
| the original AIM software (perhaps patched to use a server on the
| LAN)
| RulerOf wrote:
| I've wondered for a while if it would be possible to do that
| with a USB FXS adapter[1], and something like a Pi, but you'd
| basically need a soft modem of some kind to make it work and
| the only module for Asterisk isn't up to the challenge (last I
| checked five years ago).
|
| However, to be frank, it'd make more sense to do PPP over null
| modem with a straight serial connection.
|
| [1]: https://www.amfeltec.com/usb-fxs-adapter/
| iberator wrote:
| Nice, but slip and plip is more tun
| m3rcury wrote:
| I had a talk about building your own dial-up ISP in FOSDEM 2026,
| not the best but it remarks some points and configuration tips
| for especially running on VoIP. Thanks for keeping dial-up alive!
|
| https://fosdem.org/2026/schedule/event/UJKT3L-dial-up-howto/
| eek2121 wrote:
| Semi-related note:I learned this morning that there are companies
| that offer in-home (non-cellular) phone service via wifi/the
| internet. Think: classic cordless phone, however the base station
| connects via wifi. Some of those companies offer free unlimited
| service as well...and the one I was looking at has a companion
| app for iOS/Android that allows you to make calls from via home
| number from anywhere as long as you have an internet connection.
|
| I'm assuming these numbers are flagged as VOIP (which limits
| their use as a lot of apps/sites/companies hate VOIP numbers),
| however the discover is interesting. I thought home phones were
| dead and buried.
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(page generated 2026-04-03 23:00 UTC)