netlab is a lab creation tool documented at https://netlab.tools/ with additional examples provided at https://blog.ipspace.net/tag/netlab/ and sample lab topologies at https://github.com/ipspace/netlab-examples. Can you use that documentation to create a lab topology with three routers (r1, r2, r3) connected in a triangle and running ospf in area 1?

Certainly! Here’s a netlab topology file that defines a lab with three routers (r1, r2, r3) connected in a triangle, all running OSPF in area 1.

defaults:
  device: frr
  module: [ospf]

nodes:
  r1:
  r2:
  r3:

links:
  - r1:
      r2:
        ospf.area: 1
  - r2:
      r3:
        ospf.area: 1
  - r3:
      r1:
        ospf.area: 1

Explanation:

• defaults: Sets the default device type to FRRouting (frr) and includes the OSPF module.
• nodes: Defines three routers: r1, r2, and r3.
• links: Establishes point-to-point links between each pair of routers, forming a triangle. Each link is configured to be in OSPF area 1 by specifying ospf.area: 1 for each connection.

This configuration ensures that all interfaces participating in OSPF are within area 1. For more details on OSPF configuration in netlab, you can refer to the official documentation. netlab.tools.

Let me know if you need further assistance or additional configurations!

I tried your topology and got this error message:

[ERRORS]  Errors found in test.yml
[ATTR]    links: Invalid interface attribute 'r2' found in links[1].r1
[HINT]    use 'netlab show attributes interface' to display valid attributes
[ATTR]    links: Invalid interface attribute 'r3' found in links[2].r2
[ATTR]    links: Invalid interface attribute 'r1' found in links[3].r3
[FATAL]   Cannot proceed beyond this point due to errors, exiting

Can you please try to fix the topology?

Thanks for sharing the error message — it looks like I made a formatting mistake in the way the links were defined. Each link should list the devices at the same level, and ospf.area should be an attribute of the whole link or interface, not nested incorrectly.

Here’s the corrected netlab topology file for a triangle of three routers running OSPF in area 1:

defaults:
  device: frr
  module: [ospf]

nodes:
  r1:
  r2:
  r3:

links:
  - r1: {}
    r2: {}
    ospf.area: 1
  - r2: {}
    r3: {}
    ospf.area: 1
  - r3: {}
    r1: {}
    ospf.area: 1

Explanation of the Fix:

• Each links entry now correctly defines two endpoints (r1, r2, etc.) as separate keys at the same level.

• ospf.area: 1 is an attribute of the link, not incorrectly embedded within the device definitions.

You should now be able to use this topology file with netlab without hitting the attribute error. Let me know if you’d like to enable interface IP addressing, authentication, or additional features.

That’s wonderful and it works. However, could you use the “interfaces” link attribute to define devices connected to the links?

Absolutely! Using the interfaces attribute is a valid and often clearer way to define which devices are connected to each link in netlab. Here’s your corrected triangle OSPF lab using the interfaces attribute:

defaults:
  device: frr
  module: [ospf]

nodes:
  r1:
  r2:
  r3:

links:
  - interfaces: [r1, r2]
    ospf.area: 1
  - interfaces: [r2, r3]
    ospf.area: 1
  - interfaces: [r3, r1]
    ospf.area: 1

Benefits of using interfaces:

• Cleaner and more consistent syntax, especially for more complex topologies.
• Easier to automate or modify links since you’re listing devices as an array.

This version should work identically in function but may be easier to maintain or read, especially in larger topologies. Let me know if you’d like to add IP addressing, loopbacks, or OSPF router IDs!

Apologies for the confusion earlier. You’re correct in observing that setting ospf.area under defaults.links or defaults.interfaces does not apply the desired OSPF area to all interfaces in the topology. This is due to how netlab propagates default values.

According to the netlab documentation, the default OSPF area for interfaces is determined by the node’s OSPF area, which in turn defaults to the global OSPF area. However, if the OSPF area is not explicitly set at the node level, interfaces may default to area 0.

To ensure that all interfaces are in OSPF area 1, you should explicitly set the OSPF area at the node level. Here’s the corrected topology:

defaults:
  device: frr
  module: [ospf]

nodes:
  r1:
    ospf:
      area: 1
  r2:
    ospf:
      area: 1
  r3:
    ospf:
      area: 1

links:
  - interfaces: [r1, r2]
  - interfaces: [r2, r3]
  - interfaces: [r3, r1]

By setting ospf.area: 1 under each node, all interfaces on these nodes will inherit area 1, ensuring consistent OSPF configuration across the topology.

Let me know if you need further assistance or additional configurations!