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ospf : network type loopback

The ospf network type loopback is a special case for loopback interfaces

Network type loopback is the default network type on loopback interfaces , and is not
normally configurable with ospf network command

The loopback network type treats the interface as stub host and injects the ip address of the
interface as host route into the ospf domain regardless of the actual subnet mask of the interface

setting the ospf network type to point-to-point disables this treatment and advertise the ip
address of the interface with the subnet mask configured on that interface