OSPF design

chenhui · Created Dec 29, 2021 06:39:32

Hi @Herediano
Yes, it is possible. But there are some limitations.
When your devices are all in the same area, then you can configure that area as you want.
But if your devices are not in the same area, then you must configure the backbone area, because the router will not advertise the LSAs to other non-backbone routers. In other words, take the topology below as an example,
[R1]=====(area 1)=====[R2]=====(area 2)=====[R3]
The router R2 will not advertise the LSAs learned from the R1 to the R3, and yet not advertise the LSAs learned from the R3 to R1. In other words, R1 will not learn the routes on the R3 and vice versa.

Vlada85 · Created Dec 28, 2021 21:37:52

OSPF can work efficiently without area 0 when there is only one area. When there is a need for more areas, OSPF traffic should pass through the backbone area (area 0) to avoid the routing loop.

The backbone area distributes all routing information between the non-backbone areas. The backbone must be adjacent to all other areas, but does not need to be physically contiguous. Connectivity can be established and maintained through virtual links. All OSPF areas must connect to the backbone area.

AndresMoreno · Created Dec 28, 2021 21:25:59

Hello! Thank you for contacting us.
We are working on an answer for you.

Vlada85 · Created Dec 28, 2021 21:37:52

OSPF can work efficiently without area 0 when there is only one area. When there is a need for more areas, OSPF traffic should pass through the backbone area (area 0) to avoid the routing loop.

The backbone area distributes all routing information between the non-backbone areas. The backbone must be adjacent to all other areas, but does not need to be physically contiguous. Connectivity can be established and maintained through virtual links. All OSPF areas must connect to the backbone area.

Chanbora · Created Dec 29, 2021 03:50:12

good question

user_3134129 · Created Dec 29, 2021 05:45:09

OSPF can work without backbone area if it has only one area (non-zero number). Different areas cannot interact without area 0
If you want to use the link state protocol without a backbone, your choice is ISIS

chenhui · Created Dec 29, 2021 06:39:32

Hi @Herediano
Yes, it is possible. But there are some limitations.
When your devices are all in the same area, then you can configure that area as you want.
But if your devices are not in the same area, then you must configure the backbone area, because the router will not advertise the LSAs to other non-backbone routers. In other words, take the topology below as an example,
[R1]=====(area 1)=====[R2]=====(area 2)=====[R3]
The router R2 will not advertise the LSAs learned from the R1 to the R3, and yet not advertise the LSAs learned from the R3 to R1. In other words, R1 will not learn the routes on the R3 and vice versa.

MEGAA · Created Dec 29, 2021 13:08:18

in case of one area topology , you can configure any are number
in case of inter-area routing, you must configure area 0

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