# Datacenters

Datacenters are groups of nodes that have local network connectivity. Optionally an overlay VPN can be configured to provide local connectivity between hosts but this will result in reduced instance MTU.

### Network Mode

For nodes that have layer 2 networking on the local network and unrestricted tagged VLAN traffic can use the *Default* network mode. This uses a VLAN ID for each VPC and has very low overhead.

For nodes that only have layer 3 networking or restrict tagged VLAN traffic the *VXLAN* network mode must be used. This uses a VXLAN overlay network to get layer 2 connectivity between hosts then uses VLAN routing for each VPC. This will reduce the instance MTU by 50. When possible this should be used with jumbo frames. If jumbo frames are not used the instance MTU will be below the standard 1500.

### Private Storage

The private storage is an S3 resource that is used for instance snapshots and pod images for instances and pods that are located in this datacenter. The storage resource must first be defined in the *Storages* tab. When a file is uploaded to private storage a hash is stored in the Pritunl Cloud database. If the file is retrieved from the storage the hash is validated. This protects from malicious modification on the S3 resource but caution should still be taken to prevent malicious to potentially sensitive data on the files.

### Public Storage

The public storage's are either S3 or web based storage resources that provide images for instances and pods. Images from these storage resources will then appear as public images available to instances and pods for all users. Typically this should only be the default official Pritunl images. This will be added by default or can be manually added using the configuration below. Images from the `images.pritunl.com` domain enforce GPG signature validation, this key is included in the source code and verification is done automatically when images are retrieved from domain.

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