Fibbing: OSPF and SDN (Hybrid model)

Fibbing is an architecture that enables central control over distributed routing.
http://fibbing.net/

This architecture is based on routing protocol OSPF and its ability to set third party next-hop with some tweak

Main trick is to create multiple LSA5 for same destination with Forward address set to IP addresses which will define path to reach destination

In LSA 5 forwarding address is set to 0.0.0.0
if the ASBR redistributes routes and OSPF is not enabled on the next hop interface for those routes

In LSA 5 forwarding address is set to non-zero address if
*OSPF is enabled on the ASBR’s next hop interface AND
*ASBR’s next hop interface is non-passive under OSPF AND
*ASBR’s next hop interface is not point-to-point AND
*ASBR’s next hop interface is not point-to-multipoint AND
*ASBR’s next hop interface address falls under the network range specified in the router OSPF command.

Controller speaks OSPF with rest of the OSPF enabled network and in turn push LSA 5 with third party next hop to influence routing centrally.
Controller can be simple computer which is capable of running OSPF and able to push LSA 5 as per our need.

For our demonstration I am using cisco router as controller. Below is the topology diagram in which R5 and switch is part of controller
We are using Secondary IP address which will resolve the third party next hop set by controller
Fibbing Topology

When we try to reach IP 100.100.100.l00 from IP 40.40.40.40 we have 2 path available one via path R4-R2-R1 and other one via R4-R3-R1(marked with blue line)
R4 Before

R1 Before

R4 Before traceroute

Now with help of controller R5 we can move the traffic from IP 40.40.40.40 to IP 100.100.100.100 via path R4-R3-R2-R1(marked with red line)
R1 after