A stack overflow question and answer: Which open source OSPF-Routing implementations are available lists a few Open Source OSPF implementations:
- After many tests XORP, which was not mentioned here, was an remarkably stable and flexible open source routing solution (even if it was very complex and heavy-weight).
- Quagga worked also very well, but did not include all the features XORP did. Nevetheless, quagga is much smaller and more compact than XORP.
- The Zebra project is pretty dead – consider using Quagga instead.