SDA – Network Access Beyond the Fabric

These are self-study crib notes and may not be 100% accurate.


  • Fabric Border Nodes – devices that reside at the edge of the fabric and enable translations between the fabric and external networks.

Whenever data transfer needs to happen between an SDA fabric and an external network, a Border Node is required. These can be internal in the case of accessing our legacy networks or private data centres. External border nodes are used in the case of the Internet.

Internal Border Nodes:

  • Usually host IGP relationships with legacy or DC network equipment and will advertise out the subnets associated with SDA.
  • Act like edge nodes but rather than holding client mappings, they keep the control plane node informed of external subnets learned via IGP using the map-register process mapping those external subnets to the RLOC of the border node.

External Border Nodes:

  • Considered the default gateway of the SDA fabric.
  • When a client edge node sends a map-request to the control plane node and the control plane node doesn’t know where the destination lies, it returns the RLOC of the External Border Node.
  • The External Border Node doesn’t participate in any kind of map-register process with the control plane node.

Hybrid Border Nodes:

  • A single border node acting as both an internal and external capacity.

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