Q. Should I be using download from source or Multicast
Depends what you are doing. Install from source is the fastest when building a machine. Multicast is good for distributing to many systems when they are already out in the environment. Multicast is not good for swdist when building a few machines as it is meant to be low bandwidth impact.
Q. Should a multicast rep be designated to start with or let the system select
If you are able to, set a preferred subnet rep. It makes the process go faster and you can also increase the time for the package to sit in the cache to make this faster for futrue distributions. If you have systems that are always on then consider using software distribution preferred servers as you can then replicate the packages out to local repositories rather than relying on the multicast method.
Multicast reps come in very useful when deploying to an existing environment but you don't want to have to provision the packages out first. It is an automated method that avoids the admin work associated with preferred servers, however there are good reasons (such as raw speed) for the use of preferred servers.
Q. Why do when I send a Provisioning Template to 56 computesrs 40 go the other 16 hang, but it has now fone on for ages and they freeze
Not certain. Possibly too many for the server to handle? Probably a good one to log with LANDesk support so they can help you troubleshoot directly.
Mark Star - MarXtar LANDesk Enhancements
Home of Power State Notifier & Wake-On-WAN for LANDesk
I would add a little to what Mark said about the MDR's. When a machine gets a software distribution job, it will first check the local sdmcache to see if it has the files, then it will do a peer discovery to see if any peers on the subnet have the file, and then it will go to the core or preferred server. If you have a designated MDR you can cache software in the sdmcache folder so that clients will pull the files using peer download.
By default the MDR will keep stuff in its sdmcache directory for 14 days, and then it gets cleaned out. You can modify this in the MDR registry in this key:
HKLM\Software\Intel\LANDesk\LDWM\Distribution\Multicast\Subnet Rep Discard Period
Please note that the values are specified in seconds.
A custom vulnerability that manages this value is available at http://www.droppedpackets.org/security/custom-definitions/v_intl_landesk_discard_period.xml/view
If you manually copy files to the sdmcache folder on the MDR, the Targeted Multicast Service on the MDR needs to be restarted before it will "see" the files there for peer download.
I hope this helps, keep us posted on how it goes.