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Im trying to setup a test network with VMs to practice how static routing works, so what I thought to do is to setup two internal networks and one box with two interfaces to work as a router, here's the setup with the IPs:

enter image description here

I configured the static IPs in each box and also I added the default gateway to be adapter1 for vm-client-1 and adapter2 for vm-client-2.

Now, I'm in the last step to create the ip route, I executed in vm-client-1:

sudo ip route add 192.168.102.0/24 via 192.168.101.1 dev enp0s3

and I get this error as the output:

RTNETLINK answers: Network is unreachable.

Note: I cleared all the iptables rules with iptables -F so that the firewall is not the problem. Also, vm-client can ping 192.168.102.1 (the gateway of vm-client-2) so, I don't know why it says that Network is unreachable, help is appreciated.

  • There is no need to add this manual route, since route default route is 192.168.101.1, and this also means that 192.168.102.0/24 will be managed by this gateway... and if ip_forward is enabled at vm-router you should be able to access vm-client-2 – user34720 Jun 14 '17 at 17:55
  • I thought this was a good scenario to practice ip route add, could you suggest what can I do to make it a better scenario? Also, I don't get any response when I do ping 192.168.102.3 from vm-client-1. Do you know why is that? – VaTo Jun 14 '17 at 18:02
  • Could be ip_forward kernel variable at vm-router, OUTPUT chain at vm-client-1 firewall, INPUT chain at vm-client-2, or even vm-client-2 with an empty gateway... I know a scenario where you could learn routing: add a second interface on vm-client-1 and vm-router as intnet3 network on your hypervisor, set 192.168.103.3 and 192.168.103.1 ip addresses on those vms, and leave this network without a gateway at vm-client-1. Now, add the route: sudo ip route add 192.168.102.0/24 via 192.168.103.1.. this will create a specific route to that network ;) – user34720 Jun 14 '17 at 18:09
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    One possible reason for the Network is unreachable error is that the via-address is not configured on the dev-link, so check with ip addr if the link is correctly configured. BTW, you don't need full VMs, network namespaces and veth pairs are enough to experiment. – dirkt Jun 14 '17 at 21:03
  • @nwildner by my router already has two interfaces. you mean having 3 networks with 2 routers and 2 servers correct? – VaTo Jun 14 '17 at 22:22

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