No multicast (IGMP reports) on VPN connection

[Nick More]

Got an application that listens to (a number of) UDP multicast data streams.
Application works correct on XP and Vista.
On Windows 7 the application also works correct if the PC is directly connected to our (private multicast) network, only not if a VPN connection is used to the network. Th VPN connection itself works fine (i can ping the host machine) but no multicast is received.

Used Microsoft Network Monitor to trace the mulicast messages.
If the PC is connected directly to the network, IGMP Report messages are send if the appliaction is started.
If the VPN connection is used, no IGMP Reports are send. IGMP queries are received from the router but the PC doesn't response with IGMP reports.

Disabled the firewall but this didn't solve the problem.

Any suggestions?

 

[RedBirdDad]

What kind of VPN? PPTP or IPSec? What kind of multicast? As fas as I know IGMP broadcasts don't traverse VPN tunnels without some kind of routing.

 

[Nick More]

PPTP VPN connection / UDP Multicast

 

[RedBirdDad]

I believe you need to have a route set to forward packets to the multicast IP address. You may also need to have the VPN set to look for the multicast IP.

By default the VPN is only going to forward IP packets destined for the remote subnet it's configured for.

 

[Nick More]

I don's see why i should add a route
The route informations shows a route to the 224.0.0.0 range (the IGMP report should be send to address 224.0.0.2 for thes routers on the subnet).
Th route information is also the same as on a Vista PC that works correct.

 

[RedBirdDad]

What VPN server are using? VPN's won't forward multicast traffic unless they're configured for it. As far as I know you'd have to set the VPN server to support multicast forwarding.

 

[Nick More]

A Cisco router is used as VPN server.
There is no difference between a Vista PC that connects to this server and the Windows 7 PC except that the Windows 7 PC doens't receice any of the multicast messages (apperently not because the Windows 7 PC does't send any IGMP reports)

 

[RedBirdDad]

Which model VPN Server? What VPN clients are you using on the Vista and W7 machines? Microsoft or Cisco?

 

[Nick More]

A cisco 3845 is used as server and the Windows VPN client is used

 

[dmex]

This might help:

Enabling IP multicast: Networking and Communications

The following netsh commands display multicast group tables and troubleshooting information for interfaces.

• netsh routing ip show mfe displays the entries in the multicast forwarding table.
• netsh routing ip show mfestats displays packet statistics and input and output interface information for multicast forwarding entries in the multicast forwarding table.
• netsh interface ip show joins displays the multicast groups locally joined on each interface.

 

[Nick More]

The netsh routing commands don't seem to work either on Vista or on 7.
The 'netsh interface ip show joins' displays the join.
This is the same on Vista and on 7

If i use a testprogram that joins on address 239.1.0.99, the netsh command displays:

E:\>netsh interface ip show joins
Interface 1: Loopback Pseudo-Interface 1
Scope References Last Address
---------- ---------- ---- ---------------------------------
0 3 Yes 239.255.255.250
Interface 32: TEST network VPN
Scope References Last Address
---------- ---------- ---- ---------------------------------
0 0 No 224.0.0.1
0 1 Yes 224.0.0.252
0 1 Yes 239.1.0.99
0 3 Yes 239.255.255.250
Interface 11: Local Area Connection
Scope References Last Address
---------- ---------- ---- ---------------------------------
0 0 Yes 224.0.0.1
0 1 Yes 224.0.0.252
0 3 Yes 239.255.255.250
Interface 13: TEST netwerk via kaart
Scope References Last Address
---------- ---------- ---- ---------------------------------
0 0 Yes 224.0.0.1

 

[RedBirdDad]

Evidently the Microsoft VPN client just doesn't like multicast.

Have you tried a 3rd party VPN client like Shrewsoft?

http://www.shrew.net

 

[Nick More]

I did not try any other VPN client yet.
After a quick look at the documentation I must conclude that the 'shrew' client doesn't support PPTP. Nor does the Cisco VPN client. I don't know any 3rd party PPTP VPN client.
In the past a PPTP VPN connection was preferred since the application must receive with a latency as small as possible. I don't know what the effect on the latency will be if an other VPN protocol (L2TP of IpSec) is chosen. I might discuss this with an network expert.
At least i could try it to conclude if the muticast work.

 

[RedBirdDad]

It may not be a bad idea to at least try another client running IPSec. I'm not a multicast expert and I'm quite surprised that Microsoft's W7 VPN has trouble with multicast.

 

[Nick More]

Microsoft solved the problem with hotfix http://support.microsoft.com/kb/981637

 

[chev65]

Microsoft solved the problem with hotfix [URL="http://support.microsoft.com/kb/981637"]http://support.microsoft.com/kb/981637[/URL]

It figures there is a hotfix for this. If one person had this problem then so did thousands more, hence the hotfix. Thanks for reporting back in Nick More.