If a host provides extra IPs that I can assign to accounts in WHM, how long time should it take from the provider gives me the IPs to the IPs shows up in my WHM ?
That is really going to vary from provider to provider on how long it takes to provision them. Most providers will just send you the IPs and you will need to add them in WHM. If you have a fully managed service then they may add them for you. This is really a question for your hosting company.
Thanks, I was a bit unclear I suppose. Will the IPs use any time to propagate or something like that after the host has added them to my WHM ?
Yes, usually they will tell you what the ip range is, then you just have to add them to WHM. The provider doesn't usually add them for you.
Once the Datacenter allots you, you can add them use them immediately. Only the condition if you are unable to use may be due to the unavailability of PTR records at DC.
Well, to say. You dont have to do anything with it. But ask the DC if a IP isnt accessible even after addind that if they have PTR records for that IP. If you are really interested in understanding it. This was on first page of Google and was short and sweet http://www.zytrax.com/books/dns/ch8/ptr.html
Well, it turned out that the host screwed me. Its this guy Maleek. http://forums.digitalpoint.com/showthread.php?t=350715