The configuration of dhcp-relay expects multiple interface names to be listed. This is not required, doesn't work as specified in the documentation, and gives misleading error messages.
Specification of multiple interfaces causes isc-dhcp-relay to listen for DHCP client broadcast requests on those interfaces and has nothing to do with where those broadcasts are then sent.
When specifying a single interface, commit gives an error message:
user@router# commit [ service dhcp-relay ] WARNING: At least two interfaces are required for DHCP relay to work
Work to be done:
- Documentation at https://docs.vyos.io/en/crux/services/dhcp-relay.html should be amended to remove references to multiple interfaces.
- The error message given when committing a configuration without multiple interfaces specified should be removed