MOH multicast not working with encryption on IP Phones

[cdemont]

We deployed a cluster CUCM 8.6.2aSU2 whith cluster security in mixed mode with LSC certificate
on all IP Phones.
All encrypted calls are working fine, but we encounter problems with MOH:
- when using multicast MOH streamed from a member of the CUCM cluster, when a phone A puts
phone B on hold, phone B switches from SRTP stream to RTP stream to get the MOH stream
(becase multicast MOH does not support encryption) but phone B does not hear the music. I
could verify with a wireshark capture behind phone B that the multicast stream is received
by phone B but the DSP does not play it.
- If we de-activated encryption on phone B, then the MOH is heard correctly.
- If we keep encryption on phone A and phone B but configure unicast MOH, then it also
works correctly.

I could verify that problem on several IP phones like CP6941 and SIP only phone CP9951.
I have the latest device pack installed.

[Steven Griffin]

My next troubleshooting step would be this:

1. Turn off encryption on the phone
2. Place you call between phone A and B and place phone B on hold
3. Login to each switch/router between  and run "show ip igmp groups"

You should see phone B's IP address joining the 239.X.X.X multicast group address (this is easier if you increment by IP rather than port number)

Try the same thing again with encryption enabled.  Does it join the group?

-Steven

[cdemont]

Hi
Thanks for help.
Well yes the phone is joining the group, I can see in stream statistics on the phone that remote dest is the good multicast group but RX packets counter get stuck to 4 packets ! But the RTP stream is still there (wireshark capture)
Seems to hit a bug in phone binary but it seems too big bug. It must be related to sthg in the context but I don't see what.

Regards
Christophe

Sent from Cisco Technical Support iPhone App

[Steven Griffin]

Christophe,

In my experience, secure voice isn't a commonly deployed feature.  I wouldn't disregard it as a bug.   Try a different phone load.  Does it still occur?

-Steven

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[cdemont]

To make an update, the problem is related to some phones series, the problem does not occur with 79xx or 99xx, but the bug could be reproduced with 69xx (in SCCP).
Binaries version affected are:CP6941: SCCP 9.3.1.3
Update:
Hitting bug CSCth89840
Corrected in binary train 9.1 with binary 9.1.1 but not integrated in 9.3 yet !