Hi,

for a coupple of days i'm trying to solve how to run multicast IPTV thru Mikrotik. I'm out of my ideas, so i just try to ask here and hope somebody helps me.

I have an IP television service from my internet provider with some TV stations. I got SetTopBox for receiving, but i don't using it, coz i don't have TV. (I tried it with my LCD monitor and it works, but it is without sound). Anyway this is not my problem.

If i connect my PC straight to my internet provider cable, i can watch any TV station via VLC player without problems. Multicast session works fine, everything is just fine. But, the problem is when i connect my RB450g, which is my home router (so every home PC is connected into Mikrotik). In this situation multicast does not work. I did some research and try everything what comes on my mind, but no success.

I have latest version (4.9) on my Mikrotik, i have installed multicast package for PIM/IGMP support. I tried set up simply IGMP proxy based on Mikrotik Wiki, and tried to set up PIM/IGMP too. Actually i don't know adress of RP and when i keep default configuration (0.0.0.0 and group 224.0.0.0/4), i got error message in my log:
When everything works fine (when i'm connected directly, without Mikrotik) i used Wireshark for network sniff, and tried to figure out what i need to set in Mikrotik, but again without success :/
I'd like to ask for help here, because i rly don't know what is wrong and how to set it up correctly.

HERE is a network sniff from Wireshark (v.1.2.8 SVN Rev 32676). In time of sniff i got off every other applicanion, only VLC with stream ran.

So, can please anyone look at this and help me? If someone is interest to help, please say a word and i send you guest account on my Mikrotik and my ICQ# via PM.

Thanx a lot for any help and sorry for my english, i'm from Czech Republic


EDIT: It works via IGMP Proxy and alternative-subnets should contain stream source IP (udp packet, sniff your network or netstat -a for get it)

No one knows how to set it up?

Unless your upstream IPTV provider is running PIM AND is willing to let you become a PIM neighbor, you will have to do it with IGMP-proxy. In order to use IGMP-proxy, you will have to know the source IP address of the multicast streams and configure it in the MikroTik as allowed. It's been a while since I set this up, but I was able to make it work by following the IGMP-proxy docs on the Wiki. I'll try to setup a test...

Ok, finally it works.

The "key" was in alternative-subnets! I miss that info in mikrotik Wiki.

Anyway, thanks for reply

2 groups you are mentioning in your first post actually are from 224.0.0.0/4 and these groups should have been covered as alternative-subnets should be used only if non-standard multicast group address is used, thus indicating that consider these additional networks as multicast addresses.

weird thing is that it actually helped in your case.

hmmm... I'm not really sure, but seems like I saw the manual that said you need to add to 'alternative-subnets' not only the address of multocast group, but also the address of multicast source (i.e. ordinary unicast address of the multicast server)... need to be checked...

My provider (Cox) is sending IGMP packets to 224.0.0.1 every few seconds. Is there a discover what services are available?



I setup the IGMP proxy with the cox port being upstream but didn't know what else to do to actually find out whats out there.

I have seen much frustration and confusion with this alternative subnets option. And what's more, it seems to be not that useful at all. Yes, it can be used to filter out unwanted sources and avoid routing loops, but are these use cases so frequent? I don't know any other reasons why it's there.

I suggest that you guys ask Mikrotik to change the default behavior. I mean, wouldn't it be more logical if there was configuration required for blacklisting source address, not whitelisting, as is now? Or there should be a yes/no option that says whether all source addresses are accepted by default.

2 atis: I think, this is OK. Mikrotik "looks" for broadcasts only in his subnet, not in "whole" internet. So if source is in different subnet, you can specify that in alternative subnet settings. After that, Mikrotil "looks" for broadcast in that subnets too and if broadcast is present, he found it

For example like me:
My subnet is: 95.82.xxx.0/24
Broadcast source subnet: 83.240.xxx.0/24

multicast works with its 224.0.0.0/4 group names. That is only defined range that can be used by multicast. If for some unknown reason you want to use other addresses for multicast groups, you can specify them on alternative subnets field.

also, multicast data packet has src-address of host it originated and that is normal IP address not from that 224.0.0.0/4 dst-address is from that named address space (once it was called Class D)

if you want to blacklist something using IGMP-proxy, add entry in /routing igmp-proxy mfc with src interface, group name and empty destination. What you do is you add kernel multicast forwarding route that says - accept packets from this group on this interface and discard them. That is, if you want to drop something.

if source is in different subnet, you can specify that in alternative subnet settings.

And source address being in a different is exactly what usually happens when IGMP proxy is used. Mikrotik ISPs usually provide last-mile customer solutions, while e.g. IPTV streams usually originate somewhere far away on the Internet.

Allowing to pass the "source address check" by default does not mean that multicast data always will be forwarded. They will be forwarded only when there are clients downstream. Actually, having to pass the check repeatedly and fail probably is more expensive from the CPU point of view than having to pass the check once, succeed, and then drop all the rest of received data packets because of an automatically installed black hole route. The first is what happens now. The second option is what would happen if all source addresses were allowed by default. So if there are no other reasons for having the source address check, it seems quite unnecessary to me. (For IGMP proxy, as opposed PIM based multicast routing where the situation described happens much less frequently.)

janisk: As far as I remember alt-subnets were used for source address check only, not for multicast groups?

as i see it, problem is that IOS multicast actually is PIM-DM and that differs from PIM used in RouterOS, specifically - PIM-SM.

The difference is - PIM-DM assumes everyone wants the stream, so, it just blindly sends it out, if it receives request to stop - it will stop transmitting on the interface till request times out. So as result, request to not to send traffic should come in. While PIM-SM starts to send traffic only when request is received.

So when PIM-SM sees traffic (multicast stream) coming in (from PIM-DM), it does nothing, (it is not sending request to send traffic) with it and starts to forward it when there is request from client or if you set static MFC rule.

about alternative-subnets - documentation i was given said that this settings is there as matcher for IGMP group not address of source, since it does not matter who exactly is the source, because as i have seen, router retransmitting the stream puts there its own source address, so that address should be address of router in the same Ethernet network. For sure, i will try interrogate" someone about what exactly it does in the code.

Hi,

We are students, developing a stream project, for a IPTV system using two Mikrotiks.
We are having some problems with IGMP-proxy configuration. We have two Mikrotiks, one Routerboard 133, and another Routerboard 600A, on both RouterOS version 4.9 .

With our configuration, IGMP is working fine and is adding entries on the mfc(interfaces are joining), but the traffic is not being routed from eth1 to wlan1 as it should be.

Your scenario looks similar to ours, and we are trying to see what's wrong with our.

Can you tell us what Routerboard and RouterOS version are you using?

Thanks very much.