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I am a bit confuse in the concept of multi area ospf. I posted 2 days ago. And I was asked to leave the one interfaces of each router out of the circle. Now the center circle is area 0. The top circle is area 1 and of network 192.168.11.0/24, left circle is area 2 network 192.168.7.0/24, bottom left circle is area 3 network 192.168.8.0/24, bottom right circle is area 4 with network for PCs 192.168.9.0/24 and for servers 192.16.13.0, right circle is area 5 with network 192.168.10.0/24. Now considering the top router, will I configure it like this?:

ospf router 109
network 192.168.11.0 0.0.0.255 area 1
network 192.16.10.0 0.0.0.255 area 0
network 192.16.11.0 0.0.0.255 area 0

For top left router:

network 192.168.7.0 0.0.0.255 area 2
network 192.16.12.0 0.0.0.255 area 0
network 192.16.13.0 0.0.0.255 area 0

For left bottom router:

network 192.168.8.0 0.0.0.255 area 3
network 192.16.10.0 0.0.0.255 area 0
network 192.16.14.0 0.0.0.255 area 0

For right bottom router:

network 192.168.9.0 0.0.0.255 area 4
network 192.16.13.0 0.0.0.255 area 4
network 192.16.11.0 0.0.0.255 area 0
network 192.16.12.0 0.0.0.255 area 0

For top right router:

network 192.168.10.0 0.0.0.255 area 5
network 192.16.13.0 0.0.0.255 area 0
network 192.16.14.0 0.0.0.255 area 0

Will I include the left out interfaces in the OSPF configuration? I would be grateful if you guys would help me out as I am stuck in this for past 2 days. Thanks.

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192.16.13.0 is in area 4 on the bottom right router. So it cannot also be in area 0 on the top right router. If 192.16.13.0 is connected to the servers, then the top right router has no connection to that network.

If you leave out other networks, such as the link between top right and bottom right, then OSPF will not run on those interfaces and will not be advertised to other routers. So, to get to 192.16.13.0, top right router will either use top left or bottom left, and not the direct link to bottom right.

| improve this answer | |
  • My bad, the servers belong to network 192.16.3.0/24. So if I take into consideration the left out interfaces and correct my server network mistake, then the routers should be correctly configured for OSPF? – Ahmad Qayyum May 20 '19 at 17:45
  • The advantage of simulation tools like GNS3 or PacktTracer is that you can try it and see for yourself. – Ron Trunk May 21 '19 at 1:19

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