{{ summaryHeading }}
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Renderer{{ rendererLabel }} Addresses{{ computation.ok ? values.address_count : '—' }} Routes{{ computation.ok ? values.route_count : '—' }}
Choose the backend the target host is expected to use.
Examples: ens192, eth0, enp1s0, or id0 with a MAC match.
One address/prefix per line. Replace the example values before applying the YAML.
Leave blank only when this interface should not own a default route.
Resolvers are emitted under nameservers.addresses.
Optional suffix list for nameservers.search.
This materially changes the YAML, so it stays in the primary workflow.
{{ emit_dhcp_false ? 'Enabled' : 'Disabled' }}
Format: destination,gateway,metric,on-link,table.
Samples stay local and replace the current form.
Blank is neutral and omits the metric.
Blank omits the match block.
Blank keeps the target host's current interface name.
Blank is neutral and leaves the host default unchanged.
bytes
Off is neutral. Enable only when boot must not wait for this link.
{{ optional_boot ? 'Enabled' : 'Disabled' }}
Off is neutral. Enable only for an older environment that cannot accept route-based defaults.
{{ legacy_gateway ? 'Enabled' : 'Disabled' }} 
{{ values.yaml_text }}
FieldValueYAML pathOperator noteCopy
{{ row.field }}{{ row.value }}{{ row.path }}{{ row.note }}
RouteDestinationGatewayMetricFlagsCopy
{{ row.label }}{{ row.destination }}{{ row.gateway }}{{ row.metric }}{{ row.flags }}

The chart renderer is unavailable. The same counts remain available in the interface and route ledgers.

StatusCheckDetailRecommendationCopy
{{ row.level }}{{ row.check }}{{ row.detail }}{{ row.recommendation }}
Cloud-init Network Config Generator Build cloud-init version 2 YAML for a static VM interface, with CIDR and route validation plus warnings for risky boot assumptions.
dnsmasq DHCP Config Generator Generate a dnsmasq IPv4 DHCP scope with CIDR and pool checks plus reservations, client options and optional PXE lines for a review-ready config.
Static Route Commands Generator Generate reviewed static-route commands across host and network CLIs with CIDR normalization plus priority checks and rollback-ready delete output.
iptables Rule Generator Build bounded iptables or ip6tables commands for a packet path with explicit CIDR and port matches, persistence choices, and production-safety checks.

A remote Ubuntu host can become unreachable after one small network edit. A static address may be correct while its prefix is wrong, a gateway may sit outside the connected subnet, or a second default route may quietly compete with the intended path. Netplan collects those choices in declarative YAML and passes them to a networking backend when the configuration is generated or applied.

The document identifies an interface, assigns one or more addresses in Classless Inter-Domain Routing (CIDR) notation, and can add DNS settings and routes. CIDR joins an address to a prefix length such as 10.44.20.10/24 or 2001:db8:44:20::10/64. The prefix determines which destinations are considered directly connected, so it also affects whether a gateway is plausible without an explicit on-link exception.

Renderer
The backend that turns Netplan declarations into live settings. Ubuntu commonly uses networkd on servers and NetworkManager on desktops.
Default route
The fallback path for destinations not covered by a more specific route. Competing defaults need distinct metrics or routing tables.
On-link route
A route that treats its next hop as directly reachable even when normal prefix checks would not. Use it only when the network design requires that exception.
Search domain
A suffix that the resolver may append to short hostnames. A convenient search list can also send ambiguous names to an unintended namespace.

Stable device identity matters as much as the address plan. An interface name can change after hardware or image changes, while a unique MAC match can anchor the settings and optionally rename the interface. Custom maximum transmission unit (MTU) values, boot-optional links, and policy-routing tables solve real deployment problems, but they also make the file more dependent on the target host.

Generated YAML is a starting configuration, not proof that the machine can use it. Other Netplan files may merge with it, cloud-init may own the interface, and the selected renderer or route may not exist. Validate from a console or out-of-band session before applying a change that could cut off remote access.

How to Use This Tool:

Start from the target host's actual interface, renderer, address plan, and gateway. Sample values are documentation addresses and must be replaced.

  1. Choose Renderer and enter the Interface name. If the name may vary, add a unique Match MAC address before setting a new interface name.
  2. Enter each Static address CIDR, default gateway, DNS server, and search domain on its matching address family. Leave the gateway blank for an intentionally isolated or policy-routed interface.
  3. Add Static routes as destination, gateway, optional metric, optional on-link flag, and optional table. Use a lower metric for a preferred route only when that priority is deliberate.
  4. Review the generated YAML and warnings. Correct invalid CIDRs, family mismatches, duplicate default priorities, and out-of-subnet IPv4 gateways before copying the result.
  5. Save the YAML under the target host's Netplan directory, then run netplan generate and use netplan try with console access before a permanent apply.

Interpreting Results:

The YAML is ready for host-side testing only when validation succeeds. A warning about an IPv4 gateway outside every entered subnet may be legitimate for an unusual routed design, but it needs an explicit reachability plan. A default-route warning means two routes share the same address family, metric, and table, so their priority is not clearly expressed.

  • Confirm the interface identifier and renderer against the live host.
  • Check that every default route uses the same IP family as one configured address.
  • Treat an empty default path as intentional only for isolated or policy-routed links.
  • Use the route ledger to verify destination, next hop, metric, on-link status, and routing table before applying the YAML.

Technical Details:

Netplan version 2 nests Ethernet definitions under network.ethernets. Static addresses are sequences of CIDR values, resolver addresses and search suffixes sit below nameservers, and current default routes are expressed in the same routes sequence as other static routes. The older gateway4 and gateway6 keys are deprecated but remain available for known legacy targets.

Transformation Core:

The generated document follows a fixed mapping from reviewed network facts to YAML keys. Blank optional values are omitted rather than filled with guessed defaults.

Network factGenerated structureRule
Renderernetwork.rendererEmits networkd or NetworkManager; a blank choice omits the key.
Interface identityethernets.<id>, optional match.macaddress and set-nameA rename without a MAC match receives a warning because the intended device is not anchored.
Static address familyaddresses plus optional dhcp4: false or dhcp6: falseThe DHCP flag is emitted only for address families present in the static address list.
Default gatewayroutes[].to: default and viaAt most one gateway per family is accepted; legacy mode writes gateway4 or gateway6 instead.
Static routeroutes[]Destination and gateway families must match. Metric, on-link, and table appear only when supplied.
Resolver policynameservers.addresses and nameservers.searchResolver addresses must be IPv4 or IPv6; search suffixes must use valid DNS-label syntax.

Rule Core:

Validation stops generation when a required or structural rule fails. Review warnings cover conditions that may be intentional but cannot be proved from the entered data.

CheckAccepted ruleResult when it fails
Address prefixIPv4 prefix 0 to 32; IPv6 prefix 0 to 128Generation stops.
Route metricWhole number from 0 to 4,294,967,295, inclusiveGeneration stops.
MTUWhole number from 576 to 9,216 bytes, inclusiveGeneration stops.
MAC matchSix lowercase hexadecimal octets separated by colonsGeneration stops.
IPv4 gateway reachabilityGateway normally falls inside at least one entered IPv4 subnetGeneration continues with a warning.
Default priorityNo two default routes share family, metric, and tableGeneration continues with a warning.

The configuration model checks IPv4 gateway membership from the entered CIDR values. It does not attempt equivalent IPv6 reachability analysis, inspect existing files, or resolve whether another routing-policy rule changes the effective path.

Limitations:

Generation happens in the browser and no target host is contacted. The result cannot confirm YAML merging order, installed Netplan version, renderer availability, cloud-init ownership, device names, link state, route reachability, DNS responses, firewall policy, or whether an MTU is supported. Back up the current configuration and keep a recovery path before changing remote networking.

References: