Rad fiber "demarc" device--aka modem (?)

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TPT
Posts: 879
Joined: Mon Dec 03, 2007 3:18 pm
Location: St. Marys, WV

Rad fiber "demarc" device--aka modem (?)

Post by TPT » Sat Apr 27, 2019 5:39 pm

A state school inherited a radio station from another state operated school when they downsized. Transmitter on a mountain, was being fed by STL, but new studios are 30 miles away on the wrong side of the mountains. So they temporarily set up a feed using the station's stream to feed a computer on site to get L & R audio to an audio processor. Needless to say, not the most reliable lash-up. So they applied for and got a grant for a pair of Bric Links.

The internet provider is Frontier, but it actually is a fiber feed, through some sort of government grant. Also a public TV translator on the same mountain, so may be connected with that. Anyway, on a computer, speed looks fine, but the RAD fiber optic modem has only one working LAN connection (two jacks, both marked "user" but only one works. Bric links configured and tested in studio, working fine. OK --hook up the Bric Link up at the transmitter site--won't connect, rear panel network jack shows no activity, can't find any sign of the unit with their "switchboard" app. Try a wireless router--won't connect either, can't get the computer to work through it.

Connect the computer back to the single LAN jack on the modem--it works. What gives? Is there some way to configure--or mis-configure the modem so it only works with a particular MAC address? (I.E.--that computer?). Also wonder, since this is part of a state school system, if someone thought too much and figured out a similar way to lock things down to the point of being unusable.

Ideas?

grich
Posts: 446
Joined: Fri Sep 02, 2011 11:19 am
Location: MP89.5, Mason City Subdivision

Re: Rad fiber "demarc" device--aka modem (?)

Post by grich » Sun Apr 28, 2019 9:48 pm

It is very possible, in anal-retentive IT security environments, to find connections restricted by MAC. Someone with the school's IT geeks will have to be brought in to get this to work. Don't forget opening the appropriate TCP and UDP ports, as many campus installations block most ports. We have trouble with the state football championship venue because outbound ports in the 9000's are blocked on campus, which kills our old Tieline G3. We have a donated Access2USB, and it can only negotiate a connection using Switchboard.

Speaking of Switchboard, we ran into NAT compatibility issues with one of our BRIClink sets being used as STL...both ends had Symmetric NAT on the firewalls. From Comrex: "Symmetric NATs are not compatible with each other, nor Port. Restricted, or Symmetric FW. When using compatible NAT types Switchboard in most cases can traverse each network and establish a connection without the need for Port Forwarding rules. However, in this case, port forwarding rules are needed in order to establish a connection. You will still be able to use the Switchboard entry to connect, but you'll need the ports open regardless."

TPT
Posts: 879
Joined: Mon Dec 03, 2007 3:18 pm
Location: St. Marys, WV

Re: Rad fiber "demarc" device--aka modem (?)

Post by TPT » Mon Apr 29, 2019 12:51 pm

Kind of what I am thinking is happening, wasn't sure whether whether it could be restricted by MAC address or not. In this case, the fiber optic feed is through the state board of ed., not any local school district. Station manager was going to try to get in touch with a contact he has there.

Somewhat of a nuisance to set up...the station is 3 1/2 hours from where I live, while my IT guy is in Denver. We were trying to set things up Saturday since he didn't have take time away from his regular job. Add to that --the transmitter site is on an 1,870' ridge, last bit of the road requires a 4 wheel drive. Not completely wasted trip-- I got everything wired so that when the Bric Link fires up the station manager will just have to move two mike cables & set the composite output level, they have a mod monitor.

Next project is to install a kilowatt Nautel. I got them a CP to increase power tenfold. When grant money becomes available the GM will have the VS1 shipped to me, instead of to the school. Much easier to plug the transmitter into my network to set it up & then test into our 10 kw dummy load.

radio_guru
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Joined: Sat Oct 02, 2010 11:23 pm
Location: Illinoid

Re: Rad fiber "demarc" device--aka modem (?)

Post by radio_guru » Sun Jun 16, 2019 5:13 pm

We find this every time we get in new IP service. You need to call the ISP vendor tech support and have them either open up the desired ports or walk you through the steps in their modem's firewall when on site. ( you better have the account number, circuit ID, all security PW's and customer selected questions at your disposal when you do this.) Most modems are shipped locked down to avoid exposing ignorant customer machines to all sorts of devious actors and random ports. With a good strong PW, any mission specific codec running custom RISC software (Comrex, Tieline, ZIP, Intraplex, et al) or one running on Linux will be fine long term. Do not attempt this with a WIN machine without a very good, no exceptional, secondary firewall.

When doing this, consider the ports needed for something like an Intraplex IP link. So if you get a 2nd feed on the mountain, you can install a high reliability STL system without repeating the effort to open more ports.

Item #2, I hate, no despise with a passion needing to go through someone else's server to connect up what would be a private line. Sure it might offer Port 25 service and some diagnostics. But going all the way to some server where one has no idea where it's located is a possible multi-thousand mile hop which isn't needed and prone to network congestion and multiple points of failure. This is no different than a long distance T-1 going through multiple carriers and their least costly routing. For a STL, the link should be as direct as possible allowing for the ISP's routing.

RG

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