SRST testing

Test the SRST configuration: 

## Take down the WAN interface or add a static route to null 0 for any ip packets coming from Unified CallManager ## 

ip route 171.69.103.225 255.255.255.255 null 0

Loop start

Loop-Start:

When loop start signaling is used, a gateway's FXO interface looks like a phone to
the switch (PBX, PSTN, Key-System) it is connecting to. The FXO interface closes the
loop to indicate off-hook, just as an analog phone does when it is physically lifted
off-hook. The switch always provides battery, so there is no disconnect supervision
from the switch side. Because a switch expects a phone user (which an FXO interface
behaves like) to hang up the phone when the call is terminated (on either side), it
also expects the FXO port on the router to hang up. This "human intervention" is not
built into the router. The FXO port expects the switch to tell it when to hang up (or
remove battery to indicate on-hook). Because of this, it cannot be guaranteed that a
near-end or far-end FXO port will disconnect the call after either end of the call has
hung up.

Disable toll fraud feature on IOS 15

Router# conf t
Router(conf)# voice service voip
Router(voice-ser-voip)# no ip address trusted authenticate

Difference between Unicast and Multicast MOH

Unicast:

MOH server is commanded to generate a stream to the IP address of the endpoint receiving the stream. The endpoint is told to listen to the stream, which includes various messages depending on the protocol and the type of endpoint. When the call is to be taken off hold, the MOH server is told to stop streaming, and the held party is connected to the appropriate endpoint.

Multicast:

MOH server is always streaming the multicast stream. As such, CallManager doesn't need to tell the MOH server to do anything. The endpoint is simply told to listen to the multicast stream.