How to make VMs from external and external3 communicate on CREODIAS


This manual describes the situation when you have an instance or more instances connected to “external” typology. None of the new instances connected to new external3 typology has network connection with old “external2” typology by default. Following the steps in this article will let you create new network which will connect virtual machines with external2 and external2 networks.

If you don’t have an instance connected to “external2” typology, follow this guide: How to add Floating IP to VM from external3 pool on CREODIAS.

If you don’t have an instance, please follow this guide:How to create new Linux VM in OpenStack Dashboard Horizon on CREODIAS.

In this scenario, we use

  • one instance connected to an external2 network and

  • another instance, which is connected to an external2 network.


In order to connect those two networks, a third network has to be created.

In ProjectNetworkNetworks choose Create Network:


Provide any name for the new network, in this example, it will be called private_LAN.


Provide Subnet Name, Network Address and Gateway IP. Network address has to be different than already used networks. We have network used already in private_on_external and private_on_external2 networks so we use


We need also provide allocation pools and DNS Name Servers.


The new network setup is completed now. It will be visible in ProjectNetworks as below:


In ProjectComputeInstances there are two virtual machines on different external IPs:


For both virtual machines choose Attach Interface in Actions menu


In Networks choose newly created private_LAN.


Finish the setup by selecting Attach Interface


From now on both machines are connected through the new network. You can ping them by IPs from 192.168.8.X interfaces, which can be checked using an ifconfig command.