Hi Mirek,
Symantec does not provide a list of IP addresses for the LiveUpdate servers as the security is built in to the product. In addition, like many other software firms, we use a content provider and we cannot guarantee consistant IP addresses. Many customers have either setup an Internal LiveUpdate server using the LiveUpdate Administration Utility (LUAU) in a location that can download from Symantec LiveUpdate, setup parent servers across the boundary (creating tunnels for communication), or have created a white list entry for the Symantec LiveUpdate servers on their perimeter devices.
For more information on LUAU and to download LUAU, please visit
this page.