To preserve analog calls in an MGCP switchback event, which three commands must be configured in the MGCP fallback router? (Choose three.)
A.
h323
B.
mgcp-switchback-graceful
C.
voice service voip
D.
mgcp-graceful
E.
preserve-h323
F.
no h225 timeout keepalive
Explanation:
these additional command for call preservation when using MGCP fallback:
voice service voip
h323
no h225 timeout keepalive
Reference. CCNP Voice CIPT2 642-457 Quick Reference, 2nd Edition