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Multicast to PPP clients

Posted: Thu Jul 11, 2019 9:34 am
by vahidmajidi
Hi
As shown in the graph attached:
A. I have some UDP Data Generators (DG), which send the data (Soil Moisture, Temperature, ...) on routed paths to the Core Router (CR).
B. Monitoring Agents (MA) will connect to the CR via PPTP.
C. I need to send all the received data (UDP stream) to all MAs simultaneously.

I think I should use a form of Multicast between CR and PPTP Clients;
if I'm right, I am restricted to config multicast between CR and PPTP Clients ONLY, not on other parts of the network.
Diagram.jpg
A simplified version of the problem is like this:
Simplified.png
Clients can be any type of supported PPP links.

I don't know How to do this. Can anyone help me please ?
Thanks

Re: Multicast to PPTP clients

Posted: Thu Jul 11, 2019 12:10 pm
by pe1chl
It is not possible to do this using IP Multicast I think. You can only multicast to a multicast capable medium, and PPP isn't.
It would be possible to connect remote routers via PPTP and then do multicast routing via the PPTP links, but that is not your setup.

Re: Multicast to PPTP clients

Posted: Thu Jul 11, 2019 1:17 pm
by cdiedrich
In case the pptp clients are routers and not raod-VPN computers, you could give it a try by using BCP.
-Chris

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 11:47 am
by vahidmajidi
Thanks You for your replies.
any suggestion for a solution to the problem in general ?

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 12:14 pm
by cdiedrich
BCP or any "true" layer2 tunnel (EoIP or vpls for example) will surely do.
Is that Multicast link-local (224.0.0.0/24) or routable (everything from 224.0.1.0 upwards)? If the latter, you could surely try PIM on your concentrator and make the clients send a join request - this could easily be done with adding a default route via VPN for the clients (aka "send all traffic over VPN").
-Chris

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 1:26 pm
by vahidmajidi
Dear Chris
Users (PPP Clients) are usually windows clients, and it seems that windows pptp clients can not be bridged usung BCP.
address space design is up to me, shouldn't I use 239.0.0.0/8 range ?

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 1:29 pm
by cdiedrich
You shouldn't. That's reserved for IPv4 Multicast and will reliably mess things up in your router.
I was asking if the Multicast you want to send to the clients is in that range. And if it is, chances are high that you will have success using PIM on your router.

Here's an excellent presentation covering the concept.
Have a deeper look in the "Multicast Single Router" Concept in slides 15 and onward.

-Chris

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 2:05 pm
by vahidmajidi
I really appreciate your time, and I'm so new on this topic !!!
is it possible to explain with more detail ?

I have a data generator (address: 172.16.4.22 in private network, and directly connected to Core Router), lets call it DG.
Windows clients (anywhere on internet) will connect to the Core Router using PPTP.
I want them to receive the traffic from DG.
should I have an IP Pool and assign them IP address from 224.0.1.0/24 ?
It seems thet I have to configure PIM on my Router, right ?
and on the DG, what should be the destination address for generated data ?

I AM CONFUSED !

============================
By the way, I wrote this before you send me the Slide !
Thank you.

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 2:21 pm
by cdiedrich
Keep your address space as it is.
Then install and configure PIM your router:
Add the DG-facing interface to PIM.
Add the pptp clients to PIM with their interfaces (create pptp server bindings for each client, these can be added).
Your DG should send the multicast traffic to your router (give it static routes for the Multicast groups it is transmitting on via the local address of your router).
Make sure your pptp clients are sending all traffic via the pptp connection.

Now PIM will take care of the Multicast distribution.

-Chris

Re: Multicast to PPP clients

Posted: Fri Jul 12, 2019 5:13 pm
by vahidmajidi
Hi
I did everything, result is attached.
I noted that the receiver software is so dumb ! it just gets what comes to its listener port, from any source IP !
Result-01.png
What do you think is wrong ?
Thank you

Re: Multicast to PPP clients

Posted: Sun Jul 14, 2019 12:44 pm
by cdiedrich
Try adding a static route to your DG as follows:
224.0.1.1 via 172.16.4.17

-Chris

Re: Multicast to PPP clients

Posted: Tue Jul 16, 2019 4:59 pm
by IPANetEngineer
What is the TTL set for on the multicast source? If it's too low, it won't work. If you can't see or set it on the multicast source, then do a packet capture at the PIM RP and see what it's set to.

Run into this issue more than once.

Re: Multicast to PPP clients

Posted: Tue Jul 16, 2019 5:17 pm
by cdiedrich
That is an excellent point!
-Chris