[ISOC_KE] IP address

Not sure if this is the correct platform however am looking at a technical practicality. In Nairobi some ISP will migrate one from canopy broadband to fiber and clients will retain there public Ip addresses In some regions migration from coaxial cable to fiber you have zero chance of retaining the public ip addresses or rather this cannot be migrated over. why is this ? is it because the backbone in Nairobi is one and other regions have several backbones hence cannot move over the different backbones ? greg , joly and all any ideas ? regards, kelvin