The CentOS Virtual Appliance build of the Software Vulnerability Manager allows you to configure Proxy host and port, and proxy username and password. This configuration would suffice to forward all SVM server synchronization requests through the local Proxy, but it would not be sufficient to route YUM update of the underlying CentOS host through the configured proxy.
Flexera will improve this configuration in an upcoming version of the CentOS VA by propagating the server proxy configuration to the yum.conf file automatically. This improvement is planned for an upcoming release of the CentOS Virtual Appliance server.
Until then, customers can configure their /etc/yum.conf file additionally with the correct Proxy information that will suffice to enable the CentOS system to fetch updates through the correct Proxy.