Explanation:
http://lync70337.freeforums.org/contoso-plan-the-subnets-for-call-admission-control-cac-t42.html
TechNet CLEARLY tells, with black letters on white background:
1) A/V EDGE to get involved in CAC-related Subnet definition and 2) YES we DO use 32-bit mask...
so for New York this is 131.107.100.3/32 ...
NO .../24: why include WHOLE subnet where we only need public IP of A/V Edge?
First all, the question is 'for CAC and media bypass'.
Now, from link: http://technet.microsoft.com/en-us/library/gg398585.aspx, we know
####
Media bypass and bandwidth reservation are mutually exclusive. If a media bypass is employed for a call,
call admission control is not performed for that call. The assumption here is that there are no links with
constrained bandwidth involved in the call. If call admission control is used for a particular call that involves
the Mediation Server, that call cannot employ media bypass.
#####
For CAC itself, link: http://technet.microsoft.com/en-us/library/gg398334.aspx. Read bottom of the page, "it
is important that subnets entered during network configuration on the server are actual subnets instead of
virtual subnets". It explained why 192.168.8.0/21, 30.0/23, ..
Now considering A/V edge server, link: http://technet.microsoft.com/en-us/library/gg425827.aspx. It says: If you deploy Audio/Video Edge Servers, the public IP addresses of each Edge Server must be associated with the network site where the Edge Server is deployed. Each public IP address of the A/V Edge Server must be added to your network configuration settings as a subnet with a subnet mask of 32
NY: 131.107.100.0/24 192.168.8.0/21
LA: 192.168.30.0/23
Miami: 192.168.20.0/24
Houston: 192.168.40.0/24
The 192.168.x.x configurations as per defined in scenario.
Then we need a public network address for New York. We must not use the /32 network mask.

Explanation/Reference:

Explanation:
When defining a PSTN gateway in Topology Builder, you must define a root trunk to successfully add the
PSTN gateway to your topology.
The root trunk cannot be removed until the associated PSTN gateway is removed.

Explanation:
http://lync70337.freeforums.org/unassigned-numbers-t25.html