SRST Multicast Music on Hold groups Incrementing Port Number

[Miquel Bover]

Hello Team,

I'm triying to configure Multicast Music on Hold Groups with Incrementing Port Number in the VoIP Gateway as described in the below link:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cusrst/feature/guide/MOH_srst.html

We want to mulicast several streams using the same VoIP Gateway.

Below you can see MoH configuration in the VoIP GW:

voice moh-group 1
 moh enable-g711 "flash0:/moh_1.wav"
 multicast moh 239.1.1.1 port 16384 route 10.119.96.12 10.119.254.12
voice moh-group 2
 moh enable-g711 "flash0:/moh_2.wav"
 

The CUCM is who indicate to the IP Phone wich stream to play, based on the CUCM configured as MoH Audio server with the below configuration:

Base Multi-cast IP Address: 239.1.1.1

Base Multi-cast Port Number: 16384

Increment Multi-cast on: Port Number

When a IP Phone holds the call, if the stream "User Hold MOH Audio Source" index is 1, the multicast IP addres and port are: 239.1.1.1 port 16384

deedcpbxgw03#sh ccm-manager music-on-hold
Current active multicast sessions : 1
Multicast RTP port Packets Call Codec Incoming
Address number in/out id Interface
===================================================================
239.1.1.1 16384 4157/4157 10 g711ulaw ED0

If the IP Phone "User Hold MOH Audio Source" index is 2, the multicast IP addres and port are: 239.1.1.1 port 16392.

deedcpbxgw03#sh ccm-manager music-on-hold
Current active multicast sessions : 1
Multicast RTP port Packets Call Codec Incoming
Address number in/out id Interface
===================================================================
239.1.1.1 16392 0/0 12 g711ulaw ED0
deedcpbxgw03#

The above described works as expected, se below table link:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cusrst/feature/guide/MOH_srst.html#wp1674610

Our problem is that we cannot configure the same multicast IP addres (with different port) in diferent MoH Group, see below ouptut:

deedcpbxgw03#sh run | s voice moh-group
voice moh-group 1
 moh enable-g711 "flash0:/moh_1.wav"
 multicast moh 239.1.1.1 port 16384 route 10.119.96.12 10.119.254.12
voice moh-group 2
 moh enable-g711 "flash0:/moh_2.wav"
deedcpbxgw03#
deedcpbxgw03#conf t
Enter configuration commands, one per line. End with CNTL/Z.
deedcpbxgw03(config)#
deedcpbxgw03(config)#
deedcpbxgw03(config)#voice moh-group 2
deedcpbxgw03(config-voice-moh-group)#
deedcpbxgw03(config-voice-moh-group)#multicast moh 239.1.1.1 port 16392 route 10.119.96.12 10.119.254.12
* ERROR:
This multicast moh ip address is already in use under voice moh-group 1
deedcpbxgw03(config-voice-moh-group)#

I know changing the "Increment Multi-cast on" from "Port" to "IP Address" would have a workaround, but I cannot modify the CUCM configuration, because afect to other sites.

Have you any idea to solve this issue?

Best regards!

Miquel Bover

[Deepak Mehta]

Hi Miquel,

As per SRND "IP network routers route multicast based on IP addresses, not port numbers. Routers have no concept of multicast port numbers. Thus, when it encounters multiple streams sent to the same multicast group address (even on different port numbers), the router forwards all streams of the multicast group. "

Also for Cisco Unified SRST multicast MOH, the Cisco Unified Communications Manager MOH server can use only one audio source. 

Thanks

[Deepak Mehta]

I believe that is the reason why you cannot have same ip address for different MOH groups on same router.

[Miquel Bover]

Thank you so much Deepak!

Finally I changed the configuration to increment by IP address instead Port.

Best regards!