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New Member

multicast MoH on SRST router


As per CUCM SRND multicast MoH call details, looks the multicast MoH is care the IP address only which means not care the port number.


-cucm configure to port 16384, check mark 'port incremental', g711 codec between MoH server and SRST site IP Phones

-srst configure to 239 1.1..1 port 16444 x.x.x.x x.x.x.x

call establishment between two IP Phones in SRST site and press Hold button on one of IP Phone, the Holdee will receive multicast MoH from local SRST router with IP address

->what about the port requirement at this time? Is the Holdee receiving multicast MoH traffic from with regardness the port or must mach the port (16384) which configured in CUCM? I don't see the port number match requirement from CUCM SRND doc and want to know the exact behavior,

Advise please,

Super Bronze

Re: multicast MoH on SRST router


The phones will be instructed by CCM to listen to a particular mcast group (i.e. IP address). Apparently they don't subscribe to a particular port, so the UC SRND recommends you increment the IP Address, not port.

On CCM, you can choose between incrementing the IP Address (i.e. source 1 = 16384, source 2 = port 16384 etc), or the Port (source 1 = 16384, source 2 = 16392).

Note that the ports or IPs don't increment one at a time, they jump up depending on which codec you are transmitting etc.

As long as you have configured the gateway to stream to the same IP/port that the CCM will instruct the phones to listen to (i.e. if you are incrementing on IP and using source 2, then set it to 16384) then it will work.

See this section of the SRND:

Please rate helpful posts...


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Hi I am trying to set up



I am trying to set up multicast for music on hold on the cucm 9.



on the cucm, I enable multicast audio sources on MOH server, using base IP, and set increment multicast on " ip address"


however the multicast IP address keep changing, sometimes its, then after a while it suddenly change to etc..


here is the config on our srst router ( which specify the multicast ip is

is there any way that the multicast ip do not keep changing as its affecting the MOH at the moment.


" config for MOH"

 srst mode auto-provision none
 srst dn template 1
 srst dn line-mode dual
 max-ephones 265
 max-dn 600
 ip source-address port 2000
 timeouts interdigit 5
 system message "GlobalDial Unavailable"
 cnf-file location flash:
 time-zone 48
 date-format dd-mm-yy
 voicemail 080758831#
 max-conferences 8 gain -6
 moh "xmas_jazz.wav"
 multicast moh port 16384 route
 transfer-system full-consult
 transfer-pattern 0.T
 secondary-dialtone 0
 create cnf-files version-stamp 7960 Nov 27 2013 18:23:59



I was thinking to put a few more multicast IP,. but it only allow you to put one ( while the cucm set the IP address as increment)


OC-MHO-VG-SRST(config-telephony)#multicast ?
  moh  Set IP multicast address for use with music-on-hold from flash

OC-MHO-VG-SRST(config-telephony)#multicast moh ?
  A.B.C.D  Define music-on-hold IP multicast address from flash

OC-MHO-VG-SRST(config-telephony)#multicast moh ?
  port  Define media port for multicast moh

OC-MHO-VG-SRST(config-telephony)#multicast moh

Super Bronze

Hi RachelWhere in the post

Hi Rachel

Where in the post above I have put 'port incremental' - that means port, not IP.

Each stream from CUCM will use a different IP with your settings of 'increment IP', meaning G711, G729, etc streams of the same audio source will use different IPs, and appear random.

Use 'port' increment as instructed.


Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!