Think of scenarios where you have mergers/acquisitions where different portions of the now amalgamated network were designed differently and there may be too much pain or require too much time to redesign rather than bolt together and redistribute.
Sk. -----Original Message----- that confuses me, the logic I mean... I suppose in a single network I'd expect to see one igp for an address family (ospf or ospfv3). Not "eastcoast devices do ospf (stodgy bastards!) and westcoast goes isis!"
