To block or allow access of IP for your azure cloud service you need to write the following code in ServiceConfiguration.cscfg under </Role> tag:
<NetworkConfiguration>
<AccessControls>
<AccessControl name="test">
<Rule action="permit" description="test" order="100" remoteSubnet="192.72.174.38/32" />
<!--<Rule action="deny" description="test" order="200" remoteSubnet="0.0.0.0/0" />-->
</AccessControl>
</AccessControls>
<EndpointAcls>
<EndpointAcl role="MyApp" endPoint="Endpoint1" accessControl="test"/>
</EndpointAcls>
<!--<AddressAssignments>
<ReservedIPs>
<ReservedIP name="YourStaticIP"/>
</ReservedIPs>
</AddressAssignments>-->
</NetworkConfiguration>
Here I am allowing a specific IP and denying all IPs this is for my staging site.
Here "MyApp" - is my web role name
and "Endpoint1" - is my endpoint name as in csdef file.
In remoteSubnet="0.0.0.0/0" / section /0 is CIDR notation.