C.O.R.E. How to route through multiple routers

In C.O.R.E. 4.8 I cannot trace a route from a host (h1) connected to one router(r1) to another host (h2) on another router (r2). The two routers are connected. Something like this: h1<-->r1<-->r2<-->h2

I've tried using the OSPF and RIP services on the routers but I do not know how to correctly configure them.

Perhaps unrelated, but all services running on the routers show the following error message:
```` DATE: Mon May 13 14:54:45 2019 LEVEL: ERROR (2) NODE: 1 (n1) SESSION: 38179 SOURCE: service:zebra

validate command failed: pidof zebra ````

I expect packets to be forwarded from h1 to h2. What happens is that h2 cannot be found. Ping and traceroute between the two routers works but the terminal window shows :
Couldn't highlight next hop: 10.0.1.1 Couldn't highlight next hop: 10.0.1.2

In case you are interested, here is the code for the network:

```` node n1 { type router model router network-config { hostname n1 ! interface eth1 ip address 10.0.1.1/24 ipv6 address 2001:1::1/64 ! interface eth0 ip address 10.0.0.1/24 ipv6 address 2001:0::1/64 ! } canvas c1 iconcoords {110.0 110.0} labelcoords {110.0 142.0} interface-peer {eth0 n3} interface-peer {eth1 n2} }

node n2 { type router model router network-config { hostname n2 ! interface eth1 ip address 10.0.2.1/24 ipv6 address 2001:2::1/64 ! interface eth0 ip address 10.0.1.2/24 ipv6 address 2001:1::2/64 ! } canvas c1 iconcoords {418.0 110.0} labelcoords {418.0 142.0} interface-peer {eth0 n1} interface-peer {eth1 n4} }

node n3 { type router model PC network-config { hostname n3 ! interface eth0 ip address 10.0.0.20/24 ipv6 address 2001:0::20/64 ! } canvas c1 iconcoords {65.0 342.0} labelcoords {65.0 374.0} interface-peer {eth0 n1} }

node n4 { type router model PC network-config { hostname n4 ! interface eth0 ip address 10.0.2.20/24 ipv6 address 2001:2::20/64 ! } canvas c1 iconcoords {304.0 361.0} labelcoords {304.0 393.0} interface-peer {eth0 n2} }

link l1 { nodes {n3 n1} bandwidth 0 }

link l2 { nodes {n1 n2} bandwidth 0 }

link l3 { nodes {n2 n4} bandwidth 0 }

canvas c1 { name {Canvas1} }

option global { interface_names no ip_addresses yes ipv6_addresses no node_labels yes link_labels yes show_api no background_images no annotations yes grid yes traffic_start 0 }

option session { } ````