Verifying Multicast MoH
Since multicast is used for the streaming of MoH locally (for on-net calls) from the Cisco CME device, we can use both telephony troubleshooting and IP multicast troubleshooting commands to verify and troubleshoot MoH. Firstly, observe the behaviour of multicast group 239.0.0.1 below.
The following output of "show ip mroute" is from a steady-state - there are no calls currently on hold. Observe that group 239.0.0.1 specifies Gig0/0 as an outgoing interface, however traffic is pruned, and will therefore not be sent until an IGMP request is received downstream.
CME_ROUTER#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
L - Local, P - Pruned, R - RP-bit set, F - Register flag,
T - SPT-bit set, J - Join SPT, M - MSDP created entry,
X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
U - URD, I - Received Source Specific Host Report,
Z - Multicast Tunnel, z - MDT-data group sender,
Y - Joined MDT-data group, y - Sending to MDT-data group,
V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(172.16.1.1, 239.0.0.1), 00:01:37/00:01:52, flags: PT
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
GigabitEthernet0/0, Prune/Sparse-Dense, 00:01:31/00:01:28
In the following output, a call has been made and subsequently placed on-hold. Observe the Outgoing interface list has changed from Prune to Forward, reflected also by the flags under the multicast group. This indicates that a host (i.e. an IP phone) has requested MoH downstream via the Gig 0/0 interface, thereby removing the pruning.
CME_ROUTER#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
L - Local, P - Pruned, R - RP-bit set, F - Register flag,
T - SPT-bit set, J - Join SPT, M - MSDP created entry,
X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
U - URD, I - Received Source Specific Host Report,
Z - Multicast Tunnel, z - MDT-data group sender,
Y - Joined MDT-data group, y - Sending to MDT-data group,
V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(172.16.1.1, 239.0.0.1), 00:01:46/00:01:43, flags: T
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
GigabitEthernet0/0, Forward/Sparse-Dense, 00:00:02/00:00:00
The following output indicates the relevant excerpts from "debug ephone detail" that illustrate the messages when a call is placed on hold.
Dec 28 00:58:49.523: Skinny Call State change for DN 2 chan 1 HOLD from CONNECTED
Dec 28 00:58:49.527: SkinnyGetCallState for DN 2 chan 1 HOLD
Dec 28 00:58:49.527: ephone-2[1/2]:CallPrompt line 1 ref 9:tag 103 (Hold)
Dec 28 00:58:49.527: SkinnyGetCallState for DN 2 chan 1 HOLD
Dec 28 00:58:49.527: ephone-1[0/4]:StopMedia
Dec 28 00:58:49.527: ephone-1[0/4]:McastMoh is Supported
Dec 28 00:58:49.527: ephone-1[4]:OpenMulticastReceive 239.0.0.1 16834 DN 1 codec 4:G711Ulaw64k duration 20 ms bytes 160
In the following output of "debug ephone moh", multicast moh has not been specified under telephony-service. Compare against the following output.
Dec 28 01:02:58.803: ephone_hold_resume ignored for s2s set on dn=2 chan=1 hold=1 callID=13
Dec 28 01:02:58.803: McastMoh is Available
Dec 28 01:03:06.631: No MOH entry for DN 2
Dec 28 01:03:06.631: ephone_hold_resume ignored for s2s set on dn=2 chan=1 hold=0 callID=13
In the following output of "debug ephone moh", the multicast moh command has been specified under telephony-service. Observe the difference to the output above.
Dec 28 01:03:25.171: Startup MOH/media streams MOH:0 Media:0
Dec 28 01:03:26.919: MoH route If GigabitEthernet0/0 ETHERNET 192.168.255.99 via ARP
Dec 28 01:03:30.839: ephone_hold_resume ignored for s2s set on dn=2 chan=1 hold=1 callID=15
Dec 28 01:03:30.839: McastMoh is Available
Dec 28 01:03:32.179: MoH route If GigabitEthernet0/0 ETHERNET 192.168.255.99 via ARP
Dec 28 01:03:50.203: ifs_read flash:music-on-hold.au end of file at 493042 read 3479 = 496521
