OSPF Loopback interfaces are treated as a stub host and will only have a 32 bit host route on the other devices no matter how the subnet mask is entered under the OSPF network statement.
We will explore how we can disable this default behaviour using a few methods.
As you can see, R4 is configured with IP address 192.168.1.4 and R5 with 192.168.1.5.
We have loopback interfaces added with /24 subnet masks on R4 and R5
R4#sh run int loop0 Building configuration... Current configuration : 61 bytes ! interface Loopback0 ip address 126.96.36.199 255.255.255.0 end R4# R5#sh run int loop 0 Building configuration... Current configuration : 61 bytes ! interface Loopback0 ip address 188.8.131.52 255.255.255.0 end R5#
We are running basic OSPF Configs as follows…