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# DNS for Quorum

DNS support in Quorum has two distinct areas, usage in the static nodes file and usage in the node discovery protocol. You are free to use one and not the other, or to mix them as the use case requires.

## Static nodes

Static nodes are nodes we keep reference to even if the node is not alive, so that is the nodes comes alive, then we can connect to it. Hostnames are permitted here, and are resolved once at startup. If a static peer goes offline and its IP address changes, then it is expected that this peer would re-establish the connection in a fully static network, or have discovery enabled.

## Discovery

DNS is not supported for the discovery protocol. Use a bootnode instead, which can use a DNS name that is repeatedly resolved.

## Compatibility

For Raft, the whole network must be on version 2.4.0 of Quorum for DNS to function properly. DNS must be explicitly enabled using the --raftdnsenable flag for each node once the node has migrated to version 2.4.0 of Quorum The network runs fine when some nodes are in 2.4.0 version and some in older version as long as this feature is not enabled. For safe migration the following recommended approach:

• migrate the nodes to geth 2.4.0 version without using --raftdnsenable flag
• once the network is fully migrated, restart the nodes with --raftdnsenable to enable the feature

Please note that in a partially migrated network (where some nodes are on version 2.4.0 and others on lower version) with DNS feature enabled for migrated nodes, raft.addPeer should not be invoked with Hostname till entire network migrates to 2.4.0 version. If invoked, this call will crash all nodes running in older version and these nodes will have to restarted with geth of version 2.4.0 of Quorum. raft.addPeer can still be invoked with IP address and network will work fine.

### Note

In a network where all nodes are running on Quorum version 2.4.0, with few nodes enabled for DNS, we recommend the --verbosity to be 3 or below. We have observed that nodes which are not enabled for DNS fail to restart if raft.addPeer is invoked with host name if --verbosity is set above 3.