Skip to main content

Troubleshooting — Networking

CIDR block refused when creating a subnet​

Cause: invalid format, public range, overlap with another subnet of the VPC or with a reserved range.

Solution:

MessageFix
Invalid CIDR block (ex: 192.168.1.0/24) or Invalid CIDR format (e.g. 172.16.0.0/24)Enter an IPv4 address followed by a prefix, for example 172.16.0.0/24.
Message stating that the range must be privateUse a range within 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16.
Message mentioning an overlap (overlaps) with an existing subnetChoose a range that does not overlap the other subnets of the VPC (list in View Subnets).
Message mentioning an overlap with a reserved networkAvoid 10.244.0.0/16 and 10.96.0.0/12; prefer 172.16.0.0/12.

VPC or subnet name refused​

Cause: the name does not follow the rules, or it already exists.

Solution:

  • VPC: 3 to 16 characters, lowercase letters, digits and hyphens, starting with a letter and ending with a letter or a digit. Unique within the project.
  • Subnet: 1 to 63 characters, lowercase letters, digits and hyphens. Unique within the VPC.

The VPC stays in Provisioning​

Cause: the platform has not finished provisioning the network.

Solution: the list updates automatically; wait a few moments. If the state does not change to Ready after a few minutes, contact support, giving the name of the VPC.

The secondary interface has no address in the VM​

Cause: the platform adds the interface to the VM, but the OS does not configure it automatically (this is the case on Ubuntu 24.04); or the VM has not yet taken the change into account.

Solution:

  1. On the VM's detail page, check that VPC Networks lists the subnet and that IP Addresses contains a Secondary address.
  2. In the VM, list the interfaces: 
    ip -br link
    ip -br addr
  3. If the interface exists without an address, enable DHCP on it (netplan example in Connect a VM to a VPC).
  4. If the interface does not appear at all, restart the VM (Restart in the Actions section).
  5. If the problem persists, contact support.

Two VMs on the same subnet cannot communicate​

Cause: VMs on different subnets or VPCs, interface not configured in the OS, or OS firewall.

Solution:

  1. Compare the VPC Networks section of the two VMs: they must share the same VPC and the same subnet.
  2. Check in each VM that the secondary interface carries the address shown in the console (ip -br addr).
  3. Check the OS firewall (sudo ufw status, sudo firewall-cmd --list-all, sudo nft list ruleset).
  4. Test with the interface specified explicitly: 
    ping -c 3 -I enp2s0 <other-vm-address>

The VM lost Internet access after adding a VPC​

Cause: the OS network configuration made the VPC interface the default route.

Solution: check the default route:

ip route show default

It must go through the primary interface. If it goes through the VPC interface, disable the use of DHCP routes on that interface (use-routes: false with netplan, see Connect a VM to a VPC).

Cannot delete​

Cause: the VPC or the subnet is still used by VMs. The console lists the VMs concerned.

Solution: for each VM listed, open Edit > Network & Security, uncheck the VPC or the subnet, then Save. Then try the deletion again.