A couple of weeks ago I asked: I am trying to rewrite the system that we use to allocate blocks from our provider blocks to customers. Previously the smallest block we allocated was a class C and so this process was pretty easy but now I want to be able to optimally use our allocations and allocate blocks down to a /30. Does anyone have any ideas, or code, that will manage multiple CIDR blocks and keep track of the currently unused parts of the block and given a requirement find an appropriate allocation (while not fragmenting it like crazy). It would be also useful if it could collect together POP specific blocks so that, for example, two parts of the same class C were at the same POP. Ideas, suggestions? Well I had a number of people respond, some with ideas and some asking to find out what I found out so ... The only publically available code I was pointed at was "Tree" <URL:ftp://ftp.bt.net/pub/networking/tools/tree/tree-2.1.5.tar.Z>. This seems to handle the basic allocation OK, although I'm not sure it conforms to the APNIC's guidelines on the block size to allocate. Also it could be painful if you have a number of separate blocks to allocate out of since you must specify the block before requesting the allocation. You will also still need some other DB (lookaside file, whatever) to associate the allocation to a customer, which isn't a real drama since you need to keep all sorts of other stuff to keep the registries happy anyway :-) Some other people provided ideas on how they might do it and I have decided to follow that route, ie roll my own in perl. This will allow me to do my own "specials" and easily integrate it with the rest of my system. Thanks to everyone for the pointers and advice, Mark.