Traceroute shows the path your data takes from your device to a destination. It helps identify where latency or packet loss occurs. If PON is solid and LOS is off, traceroute can determine whether the issue is internal, access-layer, or upstream network related.
What the Problem Means
If your fibre is connected but you experience:
- High latency
- Packet loss
- Intermittent disconnections
- Service-specific issues
Traceroute helps isolate whether the fault is:
- Inside your home network
- At the access layer
- Within upstream routing
Traceroute does not test fibre light signal. It tests packet path progression.
If your ONT shows:
- PON solid
- LOS off
Then the optical signal is stable, and traceroute can help identify the next layer.
What Traceroute Actually Does
Traceroute maps each "hop" between:
- Your device
- Your router
- Your ISP gateway
- Upstream transit
- Final destination
Each hop reports:
- Response time (ms)
- Packet response
- Timeouts (if any)
Consistent packet loss or high latency at a specific hop may indicate a fault at that layer.
How to Run Traceroute (Windows & macOS)
Windows:
- 1.Press Windows Key + R
- 2.Type
cmd - 3.Enter:Code
tracert 8.8.8.8 - 4.Press Enter
macOS:
- 1.Open Terminal
- 2.Enter:Code
traceroute 8.8.8.8 - 3.Press Enter
Replace 8.8.8.8 with the affected service IP if known.
How to Interpret Traceroute Results
| Pattern | Meaning | Likely Layer |
|---|---|---|
| High latency at Hop 1 | Internal network issue | Router / LAN |
| High latency from Hop 2 onward | ISP gateway issue | Access Layer |
| Packet loss only at final hop | Server filtering | External |
| Timeouts mid-route but traffic continues | ICMP filtering | Not always a fault |
| Consistent packet loss across all hops | Network congestion | Upstream |
Not all timeouts indicate failure. Some routers deprioritize ICMP responses.
Step-by-Step Diagnostic Flow
Confirm ONT Lights
- PON solid, LOS off.
Test via Ethernet
- Avoid WiFi interference.
Run Traceroute to Stable IP
- Example: 8.8.8.8
Run Traceroute to Affected Service
- Compare results.
Look for First Hop With Persistent Packet Loss
- That hop often indicates fault layer.
Repeat During Peak and Off-Peak
- Identify congestion patterns.
If packet loss begins beyond your ISP gateway, the issue may be upstream routing.
Definition: Hop and ICMP
A router or gateway that forwards your packet along the path.
Internet Control Message Protocol — used by traceroute to measure response time from each hop.
May cause timeouts that do not represent real packet loss.
South African Context
In South Africa:
- Routing often passes through regional aggregation points
- Peak-time congestion may affect mid-route hops
- Undersea cable faults affect international routes only
If traceroute shows stable first hops but latency spikes internationally, the issue is not your fibre line.
When to Escalate
Escalate when:
- Packet loss starts at ISP gateway hop
- Multiple traceroutes show consistent mid-route packet drop
- Issue persists outside peak hours
- Wired testing confirms instability
Do not escalate if:
- Only final hop shows packet filtering
- WiFi was used during testing
Provide traceroute output when logging a ticket.
When This Is NOT the Issue
If all of the following are true:
- LOS is red
- PON is flashing
Then traceroute is not required. Signal must be restored first.
See our ONT light status guides