Plain Multicast MOH Configuration
Here, I introduce plain multicast MOH configuration.
Why plain? It's because I am not digging into the granularity of switches and routers. Hence, the configuration is from CM perspective.
More often then not, we get into MOH routing issues after it's configuration, which is mainly because we forgot to add a simple command on router.
Below are the steps to follow-
1. Check the Multicast configuration box - On the audio source, MOH server and MRG.
2. When you check Multicast box on MOH server, it asks you to either use mutilcast IP addresses or ports, choose any.
3. Verified under Service Parameters > CCM Service that the default audio source is set to the right audio source.
4. Add "ip multicast routing" command globally on router.
5. Add "ip pim sparse-dense-mode"on all L2 and L3 devices in the call flow.
Design-
Step 1 Extension 1000 is in a call with Extension 2000 (branch office).
Step 2 Extension 1000 places Extension 2000 on hold. Call Manager signals the IP phone (Extension 2000) via
the Skinny protocol to perform an IGMP join for the Multicast MoH group.
Step 3 The IP phone (Extension 2000) signals to the network that it wishes to receive the multicast stream
associated with the MoH group number. PIM is used to forward the stream from the first-hop router for
the MoH server, through the WAN, and on to the IP phone at the branch.
Step 4 Extension 1001 is on a call with Extension 2001 (same branch office as Extension 2000).
Step 5 Extension 1001 places Extension 2001 on hold. Call Manager signals the IP phone (Extension 2001) via
the Skinny protocol to perform an IGMP join for the same Multicast MoH group.
Note It is important to make sure that the audio source, region, location and Media Resource Group
List (MRGL) are configured properly for the branch office. If not, the wrong MoH audio
CODEC may be used and a separate audio stream will be sent to the branch. This defeats the
purpose of saving bandwidth with multicast.
Step 6 The IP phone (Extension 2001) signals the network that it wishes to receive the multicast stream
associated with the MoH group number. The local switch and router know, via CGMP/PIM or IGMP
snooping, that an existing stream is already being forwarded to Extension 2000. So a copy of the existing
stream is forwarded from the local branch office switch.
Step 7 When the holding phone resumes the call, the held phone sends an IGMP leave to signal that it no longer
wants the multicast traffic.
Why plain? It's because I am not digging into the granularity of switches and routers. Hence, the configuration is from CM perspective.
More often then not, we get into MOH routing issues after it's configuration, which is mainly because we forgot to add a simple command on router.
Below are the steps to follow-
1. Check the Multicast configuration box - On the audio source, MOH server and MRG.
2. When you check Multicast box on MOH server, it asks you to either use mutilcast IP addresses or ports, choose any.
3. Verified under Service Parameters > CCM Service that the default audio source is set to the right audio source.
4. Add "ip multicast routing" command globally on router.
5. Add "ip pim sparse-dense-mode"on all L2 and L3 devices in the call flow.
Design-
Step 1 Extension 1000 is in a call with Extension 2000 (branch office).
Step 2 Extension 1000 places Extension 2000 on hold. Call Manager signals the IP phone (Extension 2000) via
the Skinny protocol to perform an IGMP join for the Multicast MoH group.
Step 3 The IP phone (Extension 2000) signals to the network that it wishes to receive the multicast stream
associated with the MoH group number. PIM is used to forward the stream from the first-hop router for
the MoH server, through the WAN, and on to the IP phone at the branch.
Step 4 Extension 1001 is on a call with Extension 2001 (same branch office as Extension 2000).
Step 5 Extension 1001 places Extension 2001 on hold. Call Manager signals the IP phone (Extension 2001) via
the Skinny protocol to perform an IGMP join for the same Multicast MoH group.
Note It is important to make sure that the audio source, region, location and Media Resource Group
List (MRGL) are configured properly for the branch office. If not, the wrong MoH audio
CODEC may be used and a separate audio stream will be sent to the branch. This defeats the
purpose of saving bandwidth with multicast.
Step 6 The IP phone (Extension 2001) signals the network that it wishes to receive the multicast stream
associated with the MoH group number. The local switch and router know, via CGMP/PIM or IGMP
snooping, that an existing stream is already being forwarded to Extension 2000. So a copy of the existing
stream is forwarded from the local branch office switch.
Step 7 When the holding phone resumes the call, the held phone sends an IGMP leave to signal that it no longer
wants the multicast traffic.
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