3.6.d Implement and troubleshoot network types area types and router types

3.6.d [i] Point-to-point, multipoint, broadcast, non-broadcast

in the ccnp net acad lab manual for route (if you are heading towards ccnp, i highly recommend doing all three net acad lab manuals) the idea of a loopback in ospf taking on characteristics of a host in the routing table was stressed… that would manifest itself as a /32 in the routing table, where a /24 would be preferred… hence ip ospf network point-to-point placed on the loopback interface would make it a network… good…

not doing so in an ospf mpls network will bite you in the ass…

note, i turned off ip ospf network point-to-point on the loopback of the other pe router, but the routes still show up…

Branch#sh ip route | b Gate
Gateway of last resort is not set

D    192.168.12.0/24 [90/30720] via 192.168.45.4, 00:16:35, FastEthernet0/0
1.0.0.0/24 is subnetted, 1 subnets
D       1.1.1.0 [90/158720] via 192.168.45.4, 00:16:35, FastEthernet0/0
C    192.168.45.0/24 is directly connected, FastEthernet0/0
5.0.0.0/24 is subnetted, 1 subnets
C       5.5.5.0 is directly connected, Loopback0
Branch#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
…..
Success rate is 0 percent (0/5)

then:

PE1(config-if)#ip ospf netw point-to-p
PE1(config-if)#

and:

Branch#ping 1.1.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 72/77/80 ms

note that the routes show up in either case but they are not reachable without ip ospf network point-to-point..

more on this later