Advertising IP unnumbered in OSPF

[rayevans]

Need clarification on the following:

We run our serial intf as ip unnumbered and assign them an IP address/32 out of the same class B range we use for all other interfaces/ranges used.

We advertise the class B subnetted in the OSPF statement as:

network xxx.xxx.xxx.0 0.0.0.255 area n

We also advertise the loopback address:

network xxx.xxx.xxx.xxx 0.0.0.0 area n

My question is: Is it unnecessary to advertise the loopback address since it is included in the 1st network statement?

Why or wy not? What is the impact on the routing table?

[Gilles Dufour]

not necessary and even not recommended since this could lead to trouble.

The network command under router ospf is just there to identify which interface should participate in ospf and which area to use.

OSPF will then check the ip address configured on the interface to determine what network to advertise.

[rayevans]

Thanks for the reply.

What kind of troubles could this lead to? Do you have a specific piece of documentation I can refer to?

Also you say that the OSPF process "will then check the ip address configured on the interface to determine what network to advertise". If that is the case, why do I have to adfertise any specific network? Why not let OSPF automatically check the interface and advertise info found?