gVPC troubleshooting

This page lists common gVPC errors and how to fix them. gVPC is still being built, so this page will grow.

gVPC is in preview, and the networking.datumapis.com/v1alpha API can change.

Start with datumctl network describe NETWORK_NAME or datumctl network service describe SERVICE_NAME. Each ends with a diagnosis that names the cause and who needs to act. For more information, see Operations.

Common problems

Error or reason	Meaning	What to do
`NetworkNotFound`	The network named in the workload’s `networkInterfaces` doesn’t exist, so no Instances start.	Create the network. See Configuration.
`permission to use the network was denied`	You don’t have the `networking.datumapis.com/networks.use` permission on the network.	Ask a project administrator for the Network Admin role. See Permissions.
Instances never start, with `NetworkFailedToCreate` and `has not reached location`	The workload is attached to a network that is being deleted. A network that is being deleted can still report `Ready`.	Run `datumctl get network NETWORK_NAME -o yaml` and check for a `deletionTimestamp`. To see where the network exists, run `datumctl get networkcontexts,networkbindings`. Attach the workload to another network.
`RangeOccupied`	A network you’re deleting still has Instances holding addresses on it.	Delete the workloads attached to the network. See Delete a network.
A network is rejected for not including IPv6	`spec.ipFamilies` doesn’t include `IPv6`.	Keep the default, `[IPv6]`.
Connections between locations stall	`spec.mtu` is larger than the default of `1440`.	Keep the default MTU.
An Instance can’t reach a peer	The app listens only on IPv4, or the URL doesn’t bracket the IPv6 address.	Listen on `::` and use `http://[ADDRESS]:PORT/`. See Traffic and connecting.
`NoMatchingInterfaces`, `MultipleNetworks`, or `NoServingLocations`	A network service isn’t serving.	See Check a network service.

MTU

gVPC networks use an MTU of 1440 bytes by default. The Cloud Portal shows it on a network’s Configuration tab, and datumctl get network NETWORK_NAME -o yaml shows it in spec.mtu. The MTU is smaller than the common Ethernet default of 1500, because Datum wraps each packet in an extra IPv6 header to carry it between locations. See Segment routing.

Needs further investigation. How the 1440 MTU affects traffic between Instances hasn’t been fully documented yet. If large requests, file transfers, or TLS handshakes between Instances stall while small requests work, packet size is a likely cause: keep the default MTU, and check that the app and any tunnels inside the Instance don’t assume 1500. For an overlay or tunnel between Instances, such as VXLAN, an MTU of 1360 or less has worked in testing. Report what you find to support@datum.net.

For problems with the workloads on a network, see Compute troubleshooting.

Introduction

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Common problems

MTU

​Common problems

​MTU

Common problems

MTU