are these systems communicate to SEPM? Is the SEPM able to download and update the definition ( i.e. connected to internet)? if yes, then only client will be able to update.

there is no way of manually updating the NTP or PTP defs.

cheers
Pete

There is a way You can try to configure the Liveupdate server & try to connect your SEPM to the LUA but for that you will need your LUA to be in network that has internet connectivity.
& SEPM should be able to talk to LUA.

If you have the capability of getting onto the Internet from a different machine, Dial-up, direct connection, etc. 
You could always consider manually updating the SEPM server on a daily basis. 

http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008030710560348

This will allow you to download the necessary files for AV/AS etc. at your convenience and place them into the server whenever you are ready to do so.  It would save you the time of configuring a LUA server, the cost of the machine, etc.  As well as the leg work of; plugging it to the internet, downloading definitions, disconnecting from the Internet, connecting to the network, updating server, and than distributing the definitions. 

You could possibly do this from home or any Internet connection. 

Just my 2 cents.

Hi,

This kb will help....http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2007100820002048

Download the file daily and upload into your SEPM and it will push down to your clients in closed network.
Follow the kb i give u. Its very details. However it only updates the AV/AS. The others are not updated.

Hope it helps~