Call forwarding (for busy, no-answer, and unconditional forwarding) raises many of the same issues as call transfer. Likewise, these issues can be addressed using an MTP to simplify the H.323 signaling operations.
As you read in Chapter 7, the preferred method of handling call forwarding for Cisco CME is H.450.3. Again, Cisco CME can disable its H.450.3 feature when it detects calls from a Cisco CallManager. Under these circumstances, the Cisco CME system
Just like the call-transfer case, an MTP allows internal call forwarding to occur without impact to the H.323 call leg. Of the three types of forwardingbusy, no-answer, and unconditionalthe no-answer form
Figure 8-6. Cisco CallManager and Cisco CME Call Forwarding with MTP
You can see that Figure 8-4, which shows call transfer, and Figure 8-6, which shows call forwarding, are nearly identical. Figure 8-7 shows intersite Cisco CME call forwarding for a call from a Cisco CallManager. Compare it to Figure 8-5 for the equivalent call transfer case.
Figure 8-7. Cisco CallManager Forwarding with Multiple Cisco CMEs
For the special case of call forwarding to a voice mail system, note that the H.323 call setup for the forwarded call includes the original called number (the number of the forwarding phone). This can be used to provide integration with the voice mail system and to allow automatic selection of the voice mailbox that belongs to the forwarding phone.