Traceroute & Maps

The Network diagnostics tab of a target shows the route to the host: a route timeline, metrics, a hop table, and an interactive map. The data loads when you open the tab.

Traceroute (mtr) runs only on demand, from the tab or as part of a PDF report. Three layers decide whether a new measurement happens:

Layer	Lifetime	Purpose
Browser cache	24 hours	Reload, new navigation and browser restart show the stored result without any request to the traceroute endpoint
Server cache	5 minutes	Protects against repeated mtr runs for the same target and host
New scan	on demand	The refresh icon (Run new scan) always measures again

• Automatic scan. A stored result is reused for 24 hours after the actual measurement, not after the last display. Once it has expired, the next visit starts exactly one new scan. An open page does the same when it becomes visible again; a hidden tab never scans, and switching between Dashboard and Network diagnostics never reloads. Several browser tabs coalesce into one scan where the browser supports Web Locks or localStorage leases.
• Run new scan. The refresh icon starts a scan at any time and bypasses both caches. The server still allows one scan per target and host at a time and rejects a repeat within 15 seconds (HTTP 429, honoured by the page).
• Failures. A failed or rejected scan keeps the previous result and its time. After a failed automatic scan the page shows Outdated – new scan failed and does not retry on its own for five minutes.
• Time shown. Last scanned is the measurement time reported by the server (X-Measured-At, epoch milliseconds, also on a server-cache hit). It follows the Show dashboard times in UTC setting. A stamp more than five minutes ahead of the browser clock is replaced by the browser time, so a wrong client clock shifts the 24 hours by that offset at most.

Only successful measurements are stored. The browser cache is separated by user and target, and by the target's route destination: editing the host or re-creating a target under a reused id starts a new entry. Entries are kept as rendered fragment HTML in localStorage (at most 12 entries of 256 KiB; expired ones are dropped after 7 days) and inserted like a live response. Without usable storage the page works as before and keeps the result in memory only.

Privacy

A stored route can contain internal IP addresses and host names. It stays in the local browser profile only, holds no tokens or credentials, and is removed on logout and when another user opens a target on the same browser. Entries of deleted targets are removed by the size and age limits.

Route timeline

First hop, intermediate hops, and destination appear once each, in hop order. The first displayed hop is called First hop; it is not necessarily the machine that ran the measurement. Unknown values show —, never invented zeros.

• On narrow containers the timeline is vertical; on wide ones it is a single horizontal track that scrolls.
• Three or more consecutive hops without reply, or consecutive hops without map location, collapse into one node such as 2–4 ("3 hops without reply"). Activate the node to expand it. The hop count comes from the measured hop numbers, not from an estimate.
• Select a hop (click, tap, Enter, Space) to highlight its table row and map marker and show its details.

State	Meaning
Measured	The hop replied (partial loss is stated)
No reply	The hop did not answer. This includes silent hops between measured hops (for example ICMP blocked). No address, host name, latency or location is shown, and nothing is estimated for it
Not reached	Synthetic destination, because the target never answered

A hop without map location is not a failed hop. It is marked "Location unknown" and has no map marker.

Map

The map is drawn in the browser with Leaflet and a base map served by justUp!. No external tile service is used. Country flags load from jsDelivr; if that is blocked, the table shows the two-letter country code.

The map shows one continuous chain from the first mappable hop to the destination, in hop order. Every located hop is a node, including approximately located hops (hollow marker with "~"). A link between two reliably located hops is a solid line. A link is dashed when at least one end is estimated or approximate, or when hops in between did not answer or have no location; the hop numbers it skips are named in its tooltip. Nothing is estimated for a skipped hop: it gets no marker and no coordinates. A real geographic back-jump stays visible, and a back-jump caused by an approximate position is recognizable by its dashed link. The PDF report draws the same chain from the same data.

Location sources

justUp! picks one location per hop. Local sources come first; online services are only a fallback (see Online fallback). Sources:

• POP detection from curated hostname-code mappings and explicitly reviewed learned aliases. The PeeringDB refresh stores city-level facility evidence but never creates a hostname alias from a facility alone. Refresh status is at GET /api/admin/pop/status; UN/LOCODE import remains a placeholder.
• GeoLite2-City (offline). Without the database, traceroute still works, but such hops stay off the map. A GeoLite2 point is plotted only when its accuracy radius is at most 25 km; otherwise the location stays approximate.
• ipwho.is and, with a key, ip-api Pro (online fallback only). Their coordinates have no published accuracy and are never plotted as precise points.

Online fallback

GeoLite2 is queried first. Its result counts as high quality when it has valid coordinates, a real city (not only a region), a country code and an accuracy radius of at most 25 km. The 25 km limit is a justUp! product decision (MAX_CITY_RADIUS_KM), not an official MaxMind limit: MaxMind's radius only means that the true location lies inside it with roughly 67 % confidence. It is to be revisited with real traceroute data.

GeoLite2 result	Quality	Online call
City + country, radius up to 25 km (25.0 included)	high	no
City + country, radius above 25 km	limited	yes
City + country, no radius	not evidenced	yes
Region/state only	coarse	yes
Country only	very coarse	yes
No valid coordinates	unusable	yes

A POP/CLLI location with verified confidence counts as high-quality local evidence and also avoids the online call. A city only guessed from a hostname does not.

Unknown codes seen on on-demand traceroutes are stored as review candidates, not used for location lookup. The local GeoLite2 city/country suggestion is coarse evidence, not an exact router position. Reprocessing the same route does not add another observation, and addresses in one provider/network context do not count as independent confirmations. Candidate capture adds no external geolocation request. See PoP candidate review for the explicit review workflow.

Only public IPs are ever sent to ipwho.is / ip-api Pro (HTTPS), subject to cache and backoff; private and non-global addresses never are. Online fallback (online_geo_fallback_enabled, Settings > Network > Geolocation) switches the fallback off completely. It is read on every lookup, so a change applies at once and needs no restart.

An online result has no evidenced accuracy, so it never replaces a local position. For a coarse local result (region or country only) it may supply the place name when it agrees on the country and lies near the local position; coordinates, source and accuracy class stay local (place_source in the decision marks this text-only use). Without any local position, the online position is used and stays approximate. Contradicting sources are reported and the hop stays approximate.

The online lookups of one route run concurrently (4 workers, one request per distinct IP, 10 s budget per route). Offline results are available immediately; IPs not answered in time keep their local result. Provider lookup (ASN/ISP) is independent of this fallback.

Without a usable source the location stays unknown; justUp! does not guess. If two well-evidenced sources are more than 250 km apart, the hop is shown as approximate. Provider lookup (ASN/ISP) is separate and does not change the location. A provider that rate-limits or fails is skipped for a while; GeoLite2 remains the local fallback.

GeoLite2 license

The automatic update downloads GeoLite2-City.mmdb from the P3TERX GitHub mirror (P3TERX/GeoLite.mmdb), not from MaxMind. Make sure your use complies with the MaxMind GeoLite2 license. See Settings.