If Calico is being used for the overlay network, the commands to use are a little different.

kubectl get nodes -o jsonpath="{range .items[*]}{'Destination: }{.metadata.annotations.projectcalico\.org/IPv4IPIPTunnelAddr}{'\tGateway: '}{.metadata.annotations.projectcalico\.org/IPv4Address}{'\n'}"
kubectl get IPpool -o jsonpath="{range .items[*]}{'Destination Mask: /'}{.spec.blockSize}{'\n'}"

For example:

[root@master-node ~]# kubectl get nodes -o jsonpath="{range .items[*]}{'Destination: '}{.metadata.annotations.projectcalico\.org/IPv4IPIPTunnelAddr}{'\tGateway: '}{.metadata.annotations.projectcalico\.org/IPv4Address}{'\n'}"
Destination: 192.168.77.128	Gateway: 10.1.151.30/24
Destination: 192.168.84.128	Gateway: 10.1.151.31/24
Destination: 192.168.247.0	Gateway: 10.1.151.32/24
Destination: 	Gateway:
Note: The above does not provide the netmask to use for the Destination Address Space. By default, Calico uses /26 but this can be verified using the following command.
[root@master-node ~]# kubectl get IPpool -o jsonpath="{range .items[*]}{'Destination Mask: /'}{.spec.blockSize}{'\n'}"
Destination Mask: /26
Destination Mask: /
[root@master-node ~]#

Routes to add to the LoadMaster (in System Configuration > Network Setup > Additional Routes):

Destination

Gateway

192.168.77.128/26

10.1.151.30
192.168.84.128/26 10.1.151.31
192.168.247.0/26 10.1.151.32
Note: The subnet mask defaults to /26 for Calico.