Mulicast not working between VLANs using VLC 0.8.1

[Phil]

Hi,

I've been using VLC to stream DVDs over our company LAN via multicast, however I'm extperiencing an interesting problem.

The multicast works fine when the server and clients are on the same VLAN, but when they're on different VLANS (subnets), I can't receive the stream. I have IP multicasting enabled on the router(s) between the VLANs running DVMRP.

Using a packet sniffer, I can see that the multicast traffic is routed correctly to the clients VLAN but it just wont play - nothing happens in the client.

Other multicast applications work fine at the same time over this network.

Has anyone seen this before, or can anyone give me an explanation as to why the VLC client and server don't work in this scenario.

Thanks!

[markfm]

Couple thoughts:
1) Do you have ttl set high enough? Perhaps it has trouble bridging, as a VLAN setup may act like a bunch of routers -- ttl getting decremented.

2) Do the clients in the second segment by chance have multiple Ethernet NICs? If they do, you may need a "route add" kind of command at the clients, to tell them which interface to go to to listen for multicast.

[Phil]

Thanks for your thoughts and help.

I have tried a range of values for TTL but no joy.

Also, the clients only have one NIC. Multicast works fine when the server and clients are on the same segment.

One more thing, I made a mistake in my original post. The router is actually not delivering the multicast traffic onto the remote segment for VLC generated traffic. However other multicast traffic is, which leads me to believe its got something to do with the way the VLC client requests the multicast stream.....

Any ideas anyone?

[markfm]

Perhaps you don't have multicast forwarding turned on for the router at the server side, for the specific IP you are trying to send the video on?

At least with Cisco routers, multicast forwarding has a lot of flexibility, easy to forward anything from a specific IP to the entire Class D space.

In my environment I use Cisco, no problem forwarding multicast over dedicated segments. The only gotchas at all were to make sure that --sout--UDP-ttl is > 0 and that the routers themselves were using IP Plus (since multicast isn't available in the Basic version of the IOS).

You might want to use --sout-UDP-ttl 4

Are the client PCs configured properly for their gateway?

Also, I presume you've already done this, but if not please make sure that you have coordinated with your company's IT staff -- they can be a bit perturbed if they see a bunch of multicast

[Phil]

Yep multicast forwarding is enabled and working - I can forward / route multicast traffic from other multicast apps. But VLC traffic is still not being forwarded correctly. I'm actually using Alcatel Omniswitch 7700 routers.

I noticed VLC is using IGMPv3. One thing about these routers is that IGMPv3 is a pretty new feature. Using the winXP VLC client, Is there any way I can force the client to use IGMPv2?

To comment on your other suggestions-
- Yep, the clients have their gateways set up correctly
- I'm running this in a lab environment, so there's no IT department issues!

[MariaMaggio]

Hi phil,
I have your same problem.
Do you have resolved it?Can you help me please?
Thank you in advance.

[Moacir]

Using a sniffer I found that if we setup the stream TTL via GUI interface, it doesn’t work. The stream is sent with a TTL 1 and so the routers will not forward it to any other interface. However, if you start VLC via command line and change the TTL (i.e.: --ttl=5) then the stream packets will have the desired TTL.

Using Alcatel a 7700 you should enable ip multicast switching and then a Multicast Routing protocol (for testing I would suggest DVMRP since it is easier to setup and understand). The commands are:

ip multicast switching
ip load dvmrp
ip dvmrp interface <interface ip> (where the <interface ip> is the VLAN router IP)
ip dvmrp interface <interface ip> (for all interfaces that you want to enable DVMRP)
ip dvmrp status enable

Depending on your AOS, it is possible to have the 7700 running IGMP-V3. The command is:

ip multicast igmp-proxy-version v3

It should work. I strongly suggest that you make sure your streaming packets have a TTL higher then 1 (It should have a value equal to your network diameter). So use a sniffer on the server (i.e.: Ethereal) and take a look on the stream packets TTL.

I hope it helps.

I was in a lab studying Multicast for the ACSE, trying to use VLC to stream MP3 to a Windows Media Player (WMP). Don’t know how to do it even if the VLC and WMP are in the same subnet. Do you know if it is possible?

Thanks and good luck.

mferreira@comstore.pt

[Guest]

Hi Moacir,
thank you very much about your answer.

I use the "vlc --ttl 5" command in the line command, so I'm successful to set ttl.

Sorry but I use vlc in all computers because I use linux and it works perfectly in the Lan.

I use a Cisco router and I apply ip multicast routing and pim dense mode in all interfaces.
Now I have a problem : the stream have to go outside University Lan and it has to go across a Cisco firewall.
The problem is that a computer (connected through VPN client to the LAN with IPSec support) isn't successful to see the stream.
What do you think?

Regards.

[MOacir]

Hi,

I am glad you could fix the problem with the TTL.

I am not very knowledgeable in VPN’s but, if I am not wrong, you won’t be able to multicast over an IPSec tunnel. An IPSec tunnel creates a one-to-one relationship where you have a one-to-one secret key in between the tunnel endpoints to encrypt the data that will cross the tunnel. The multicast behaviour is just like a standard broadcast where a packet is sent to everyone that is listening to it. Since every IPSec tunnel connection will have a different key negotiated during the IPSec tunnel setup, then it should not be possible to broadcast a packet to everyone once each tunnel has a different key. In a quick search at Cisco’s site I found:

“… Multicast traffic can only be sent to a physical or virtual interface, and IPsec does not represent an interface. For traffic intended to be multicast to many recipients, Pope recommends configuring routers to encapsulate IP packets in a Generic Routing Encapsulation (GRE) tunnel and then encrypting the GRE tunnel in IPsec.”. This would solve your problem crossing multicast traffic in between sites.

If the traffic is in between two sites, then you could use PIM Sparse Mode and setup a RP (rendezvous point) on the remote site. In this configuration your local BSR (Bootstrap Router) should receive the multicast traffic, send it to the RP via unicast (so cross the IPSec tunnel as any pother traffic) and then the remote RP would multicast it locally in the remote site. While I think this can be done via GRE tunnel, I am not sure if an IPSec tunnel would allow it, I never tried!

Be careful using PIM Dense Mode over the WAN. If you have too many streams it can just clog the WAN link before pruning back the unwanted multicast programs.

Finally, don’t bother about my question regarding WMP. I found that the WMP has a proprietary way for receiving a multicast stream. But since that are always different approaches for solving a problem, if anyone reading this knows how to do it please respond to my posted question.

I hope it helps. Good luck!

Moacir

[billytk06]

hi,

If there is a shortcut on desktop, open the properties.. It must be like "C:\Program Files\VideoLAN\VLC\vlc.exe" --intf wxwin

after this line, add a "--ttl 10" you must ttl value according to your network diameter..

your shortcut will be

"C:\Program Files\VideoLAN\VLC\vlc.exe" --intf wxwin --ttl 10

this will solve ttl issue on GUI

best regards.