3-tier Topology with OSPF

[littleyoda]

Does anyone see any issue with this design using a 3-tier topology within OSPF single area 0? The core switch connects to the distribution layer via L3 port-channel over point to point OSPF.

[balaji.bandi]

if p2p interface Layer 3, then setting everything to be a point-to-point is a good option to control OSPF neighbourship.

[pman]

Hi,
This topology designed for LAB or production?

[littleyoda]

This is for production. Already did it in lab.

[pman]

So I suggest adding in all routers:
- router ID (missing in rtr-01 for example)
- Different authentication for each neighbor
- Configure the OSPF auto-cost reference bandwidth

about the topology:

it would be nice if we could know the data flow from the L2 switches through rtr routers to the destination.
I see that the both rtrs are not connected to each other, and it is not clear if anything is connected at their ends.
This means that-- csw will see twice default-route (one from each rtr).

Is the destination from the L2 switches locate in both rtrs?

Are all routers / switches located in the same geographical location (for example: all routers/switches in the same DC) or some of the links are WAN interfaces (for example: connected to ISP)?

[paul driver]

Hello

Only that it looks like a single point of failure is CSW-01, unless it is vss/vpc or even stacked?

[littleyoda]

Yes it is VSS. We are planning to run additional fiber to cross-connect the wan edge for further redundancy.

[Giuseppe Larosa · Accepted solution]

Hello @littleyoda ,

if the port-channels 101 and 102 are directed to distribution switches, how are supported the OSPF neighborships with ASBR routers ?

Have you defined SVI interfaces or routed ports to support them, seeing that you are using OSPF network point to point there is no direct L2 communication between the two routers via the core switch ?

As noted by @paul driver  the Core switch is a single point of failure unless it is a VSS or SVL pair or a stack.

A link between the two ASBR routers could also help in providing more fault tolerance.

Hope to help

Giuseppe

[littleyoda]

Yes so the from the routers to core are point-to-point OSPF over L3 transit VLANs. From the core to the distribution, point-to-point OSPF via L3 port-channels.

I have since deployed this with no issue. Thanks for the help.