I've the following need:

• a first LUA downloads the contents from public Symantec servers;
• a second LUA downloads the contents from the first LUA;
• SEP Manager, Mail Secuirity and so on download contents from the second LUA.

Is this possible?

Though it is possible to configure LiveUpdate Administrator to download needed updates from another LUA server, it is generally not recommended to use this configuration. When "daisy chaining," internal servers will not be taking advantage of the very latest updates and protection definitions available from the Internet source servers. To keep all clients up-to-date with the latest available contents, Symantec Technical Support recommends instead to configure the one external LUA 2.x server with multiple Distribution Centers throughout the network. Using a Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP) or Windows File Share (SMB) server, clients can retrieve the necessary updates from these convenient locations

Configuring LiveUpdate Administrator (LUA) to download updates from another LUA Server

Possible

Configuring LiveUpdate Administrator (LUA) to download updates from another LUA Server

http://www.symantec.com/business/support/index?page=content&id=TECH105741

Thumbs Up  to the above posts.

While possible, Symantec don't recommend it.  Have you considered replacing the "Second LUA" with a Distribution Centre (DC) instead?

http://www.symantec.com/docs/TECH142789
http://www.symantec.com/docs/TECH132545

This DC is essentially just a HTTP(S)/FTP/UNC location the "First LUA" will push content to.  Clients can then download defs from the DC.

Hi diabolicus23,

As per the above- it is possible, but I do not recommend it.

A Helpful LiveUpdate Administrator 2.x Analogy
https://www-secure.symantec.com/connect/articles/helpful-liveupdate-administrator-2x-analogy

Hello,

just replace the first LUA with a remote LUA Distribution Center:

https://www-secure.symantec.com/connect/articles/configuring-distribution-center-lua

LUA + Remote Distribution Center could be a good idea...

How is the network flow in that case?

1st step) LUA connects to Symantec public servers and download definitions via HTTP

2nd step) LUA put contents to the remote Distribution Center via HTTP

3rd step) SEPM and so on connect to the remote Distribution Center via HTTP to download content

Is this correct?

Could you explain me the connection flow (source - destination) of the different phases?

Thanks!
 

That's pretty much it tbh, you've got it right.

1. During the LUA's Download job, the traffic is initiated by the LUA out towards Symantec LiveUpdate
2. During the Distribution job, the traffic flow is, again, initiated by the LUA towards the internal Distribution Centre
3. During the SEPM's own LU attempt, the traffic flow is initiated by the SEPM to the Distribution Centre