In the past I setup FreeRADIUS, BRASes, framed IPs and the like. I knew a little bit about PPPoE – But I’d never dug into the ADSL / VDSL side in any great depth, and always felt like a bit of a blind spot. But as fewer and fewer DSL lines are in service, I figured it was unlikely to change.
And then I paid $20 for a DSLAM and so now here I am in the lab with a VDSL2 DSLAM and a VDSL modem.
The unit in question is branded “Versa Technology” but looks like it’s actually made by Proscend who make the crazy ADSL-modem-in-an-SFP SFPs.
I’d expected this to be a long post, but it turns out, DSL is pretty simple (at least above the physical layer).
I plugged in the DSLAM, loaded a line profile for VDSL onto the port and plugged an old modem/router I had in (I’d scavenged the cellular modem out of the router – that’s why it’s naked).
I set the DSLAM to get it’s management IP on DHCP, and on another machine logged into the ADSL modem, and just like that, the modem had internet – It’d just grabbed an IP of my lab subnet on DHCP, and the DSLAM just acted as a dumb layer 2 device.
I started digging around in the menus, after what I’d read about VPI/VCI and the like I was expecting to see all the complex black magic that goes into getting SHOWTIME / Sync on fencing wire, but there’s just not that much to it.
When it comes to the physical layer encoding stuff, that’s where the black magic does happen – clearly a lot can go into the line profile for a given local loop. I’ve got a Fluke Copper Pro and can “profile” a line to see what the ideal line conditions are, but as this is just plugged directly into the RJ21 breakout panel, there’s not exactly a lot to tune there.
Of course most operators don’t just run DHCP to give out IPs to customer’s modems, they’d instead use PPPoE or IPoE.
So I set that up on my Mikrotik as the BRAS and CGrateS as my RADIUS server, and turned it on in the modem settings, sure enough in came the PPP request.
Which the BRAS dutifully sent to the RADIUS server, which “did the needful” and off we went.
So here I am – Working VDSL. I’ll be honest, I expected this to be a bigger challenge than it was and I’m not sure where else to go from here – Not much to explore or play with, other than adding voice on top (because nothing says legacy tech like POTS on DSL).
When I picked up the DSLAM I also got myself a CMTS – I know zero about DOCSIS but that’s the next project.