This configuration is mandatory to add the SIP Phones for SRST. Without the commands that you have mentioned here, the router would not allow you to add the voice register pool and throw the following error:
#voice register pool 1Pool tag too large, ...
Max-pool and Max-dn are mandatory when you are configuring a voice register pool. Without adding max-pool and max-dn, the router would not allow you to add the voice register pool 1 and throw the following error
Pool tag too large, maximum 0
Plea...
