Gradually, our company raises the question of replacing the core network. In the head office there is an ancient 2851, in remote offices of the 800 series, remote offices are connected via DMVPN. I would like to replace the core with hp, in connection with this question, read that hp has similar DVPN technology, is it possible to integrate hp and cisco 800 series without replacing equipment in the branches? Or if not, advise the router to replace the 2800, not cisco.