Difference with regards to starting the OSPF process

[mortojjesse]

I would like to ask the forum..

What are some advantanges/disadvantages of starting the ospf process like this:

EXAMPLE 1:

router ospf 1

network 10.10.0.0 255.255.0.0 area 0

EXAMPLE 2:

router ospf 1

network 10.10.10.10 255.255.255.255 area 0

As I understand it, in example 1, I am configuring the OSPF process to start for any interface on the device that falls under the 10.10 /16

In example 2, I am starting the ospf process for "just" the interface configured for 10.10.10.10.

I believe there is more control using the 10.10.10.10 network statement but what kind of control? Why would it be a bad idea to start OSPF for all interface under the 10.10 /16 if all interfaces will be participating in OSPF?

Thanks!

jm

[Edison Ortiz]

You have more control with a /32 entry because you can avoid OSPF adjacencies with same devices multiple times.

For instance, you have a switch with multiple virtual interfaces and they are all within the subnet you've specified then you will have that many OSPF adjacencies.

You can still use the /16 entry under these conditions along with the passive-interface default and no passive-interface on the desired interface.

At the end of the day, it's just a matter of choice. With recent IOS releases, you can even configure OSPF right under the interface instead of having the subnets listed under the routing process - similar how is done with ISIS.

Regards,

Edison

[mortojjesse]

Thank you for the reply Edison. I will lab this up and look as you described.

Much thanks.

jm