Agent based installation fails during the 3+1 deployment. I found that the Ingress operator degraded due to insufficient worker nodes and for 3+1 deployment we need to define one worker node.

Always

1. Create agent.iso (openshift-install agent create image) using install-config.yaml and agent-config.yaml (PFA sample files)
2. Deploy a 3+1 cluster using agent.iso
3. Execute "openshift-install agent wait-for install-complete" command to wait for install complete.  

The "default" ingress controller reports Degraded=True: DegradedConditions: One or more other status conditions indicate a degraded state: PodsScheduled=False (PodsNotScheduled: Some pods are not scheduled: Pod "router-default-f5b4499bd-6q5n7" cannot be scheduled: 0/4 nodes are available: 1 node(s) didn't have free ports for the requested pod ports, 3 node(s) didn't match Pod's node affinity/selector, 3 node(s) had untolerated taint {node-role.kubernetes.io/master: }. preemption: 0/4 nodes are available: 1 node(s) didn't have free ports for the requested pod ports, 3 Preemption is not helpful for scheduling. Make sure you have sufficient worker nodes.

3+1 deployment should be successful.