OSPF Concern with exam SIMS

DANMOH009

I hope can explain this right, basically im a little concerned im doing things correctly because some of the sims ive been doing as practice in packet tracer are not showing up as 100% complete, even though my network is all working correctly.

Here goes...

My main concern is when configuring ospf networks. Lets say i have 3 routers all serial linked up and connected to one another using OSPF, each router has a lan behind it.

so each lan is
R1 has 192.168.1.0 /24
R2 has 192.168.2.0/24
R3 has 192.168.3.0/24

Now all routers are connected with a /30

so R1 to R2 10.10.10.0/30
R2 to R3 10.10.10.4/30
R3 to R1 10.10.10.8/30

Now when i am configuring ospf on R1

i would do the following:

Router ospf 1
Network 10.10.10.1 0.0.0.0 area 0
network 10.10.10.9 0.0.0.0 area 0
network 192.168.1.0 0.0.0.255 area 0
(then passive int on the lan)

Now firstly im quite convinced this is the right way to do things as OSPF just advertises the link to send LSAs on, and to be honest it works.

but im a bit worried that i should be advertising the /30s a bit different

i.e

network 10.10.10.0 0.0.0.3 area 0


my question really is, am i doing it the right way??
do some sims score differently dependent on the way/command u input???
when going into the exam should i continue to do things the way i am or do i change my approach???
will the later way even work???? (i dont think it does)


Any help would be great,


Thanks

Daniel

lantech

Does it say give specifics as to what is not complete? Without the actual configurations it's hard to tell what you are doing wrong.

DPG

You are setting it up correctly by using the most specific inverse mask in your OSPF network statements. The network statement inverse mask does not have to match the subnet mask of the interface that you want participating in OSPF.

The only reason you would want to use a less specific inverse mask is to match multiple interfaces:

interface fa0/0 - 192.168.0.1/24
interface fa0/1 - 192.168.1.1/24
interface fa0/2 - 192.168.2.1/24
interface fa0/3 - 192.168.3.1/24

router ospf 1
network 192.168.0.0 0.0.3.255

MrBrian

Yes, just like DPG said ^... The network statement commands within "router ospf x" just tell ospf on which interfaces to run..

So if you do the full interface IP and a mask of 0.0.0.0, then ospf will ONLY run on that interface..

Note that the network statement here doesn't tell the router what network to advertise, just which interface that you want to add to the ospf process. Once OSPF is running on an interface, then it will advertise the network the way it is configured, by default (it doesn't do auto-summary).

For example:
If you wanted to add fa0/0= 192.168.1.0/24 to the OSPF process... you could do "router ospf 1," then "network 192.0.0.0 0.255.255.255 area 0" and this would cause ospf to run on int fa0/0 (and any other interfaces on the router that had 192.x.x.x, if you had them). However, OSPF will advertise to any OSPF neighbors that is has 192.168.1.0/24

DANMOH009

Ok thanks,

So basically the method is correct at the moment. I haven't got any examples of yet lantech, i'll let you know.

Cheers guys.