If you are unsure, the simplest way to check if an overlay network is used and pods are not routable is to view the pod IP addresses and compare them to the IP addresses of the nodes. If these are on a different network space then routes must be added.

For example:

[root@master-node ~]# kubectl get nodes -o wide

NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
master-node Ready master 46d v1. 19.2 10.1.151.30 <none> CentOS Linux 7 (Core) 3.10.0-1127.19.1.el7.x86_64 docker://19.3.13
node-1 Ready <none> 46d v1. 19.2 10.1.151.31 <none> CentOS Linux 7 (Core) 3.10.0-1127.19.1.el7.x86_64 docker://19.3.13
node-2 Ready <none> 46d v1. 19.2 10.1.151.32 <none> CentOS Linux 7 (Core) 3.10.0-1127.19.1.el7.x86_64 docker://19.3.13

[root@master-node ~]#

[root@master-node ~]# kubectl get pods -o wide

NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
azure-vote-back-59d587dbb7-x297k 1/1 Running 1 3d 192.168.84.150 node-1 <none> <none>
azurefront-5f47b44b9b-nhdwb 1/1 Running 1 3d 192.168.247.14 node-2 <none> <none>
frontend-6c6d6dfd4d-6xzpd 1/1 Running 1 3d 192.168.247.2 node-2 <none> <none>
frontend-6c6d6dfd4d-g26cb 1/1 Running 1 3d 192.168.247.1 node-2 <none> <none>
frontend-6c6d6dfd4d-qbbsv 1/1 Running 1 3d 192.168.84.155 node-1 <none> <none>
redis-master-f46ff57fd-jjhwx 1/1 Running 1 3d 192.168.84.153 node-1 <none> <none>
redis-slave-bbc7f655d-5xnkk 1/1 Running 1 3d 192.168.84.156 node-1 <none> <none>
redis-slave-bbc7f655d-n9vgh 1/1 Running 1 3d 192.168.247.12 node-2 <none> <none>

In the above example, it is clear that the PODs are on a different network to the nodes.