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A timeout, a traceroute asterisk, or a TCP retransmission is a reason to investigate—not proof that your virtual dedicated server (VDS) is dropping forwarded packets. To locate a suspected loss, identify the affected flow and compare timestamped captures at two or more controlled points. A packet visible at one point but absent at the next narrows the boundary; it does not identify a particular router or network owner unless you can observe that part of the path.
What the first symptoms do—and do not—prove
Start by describing what you observed: an application timeout, a slow transfer, a probe timeout, or TCP retransmissions. These symptoms can indicate a delivery or acknowledgment problem, but they do not by themselves show where it occurred.
| Evidence | What it can establish | What it cannot establish alone |
|---|---|---|
tcpdump at one interface |
A packet was or was not visible at that capture point during the capture, subject to the filter and capture conditions. Output can show endpoints, ports, flags, sequence and acknowledgment numbers, and packet lengths. tcpdump(8) | What happened beyond that capture point. |
| Captures at two controlled points | Whether matching packets are visible at one point and absent at another, narrowing the interval where visibility changes. | The exact device or party responsible within an unobserved interval. |
traceroute |
Which probes received hop responses and the reported round-trip behavior. traceroute(8) | That a hop which does not respond is dropping ordinary transit traffic. ICMP replies may be filtered or rate-limited. |
ss |
Socket state and timer details, including retransmission-related timers. ss(8) | The network location responsible for a retransmission. |
| TCP retransmissions | TCP is retrying as part of its reliable, ordered delivery behavior. tcp(7) | The packet’s exact path or the segment where it disappeared. |
How to investigate a suspected VDS packet drop
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Define the affected flow
Record the source and destination addresses, address family, protocol, port, direction, and symptom time window. This identifies what to capture and helps avoid a filter that excludes the traffic in question.
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Record the socket state
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ssand save the relevant output, including retransmission-related timer information if shown:#1 Best Overall
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ss -tinThis records connection state; it does not locate the network segment causing the problem.
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Probe the route to the actual destination
Run a route probe and note its method, selected port, responding hops, and time. For traffic using TCP port 443, an illustrative Linux command is:
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traceroute -T -p 443 example.comReplace the destination and port with values appropriate to your case. Linux
traceroutecan use TCP SYN probes and a selected port. An asterisk means a probe did not receive a response; routers can throttle or filter the ICMP replies used to report hops even when they continue forwarding traffic. If later hops respond, that is useful context, but a missing response at one hop is not proof of a forwarding drop.Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy. -
Capture the relevant traffic on the VDS
Capture during the symptom, using a filter that matches the destination and protocol or port. For example:
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tcpdump -ni eth0 -s 0 -tttt 'host 203.0.113.10 and tcp port 443'Replace
eth0, the example address, and port with the actual interface and flow details. Capture privileges may be required, depending on local configuration. The timestamped output can help you follow packet direction and TCP sequence and acknowledgment progression. Check that the capture filter includes the traffic you need. -
Repeat the capture at another controlled point
If possible, capture the same flow at the destination host or an adjacent network device. Compare matching packets across the captures by flow, direction, timestamps, sequence and acknowledgment behavior, and packet presence. If a packet appears at the first point but not the second, you have narrowed the interval in which visibility changes. You have not necessarily identified a particular router or who operates it.
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Ask for evidence beyond the guest when needed
A capture on the VDS interface establishes what was visible there; it cannot establish what happened later in the provider network or at the remote host. If the remaining interval is outside the systems you control, request provider-side observations for the same flow and time window. Guest-visible evidence alone does not show what happened at a provider’s hypervisor, virtual switch, or host-side network.
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How to read a traceroute asterisk
Linux traceroute elicits time-exceeded responses from gateways as probes progress through the path. A hop that shows no response may have filtered or rate-limited those replies, or the probe may otherwise have gone unanswered. That result is distinct from proving that ordinary application traffic was not forwarded.
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When useful, choose a probe protocol and port closer to the application flow, such as TCP probes to the relevant service port. Treat the output as supporting evidence: it reports responses to probes, not a packet-by-packet map of application traffic.
What makes two captures useful evidence
Captures are comparable only when they let you identify the same traffic and account for how it was observed. Check these factors before drawing a conclusion:
- Observation point: Record which interface or host produced each capture.
- Direction and flow: Match source and destination, address family, protocol, ports, and traffic direction.
- Time: Capture during the same symptom window and retain timestamps. Clock differences between systems can complicate timing comparisons.
- Packet progression: For TCP, compare sequence and acknowledgment behavior as well as packet presence.
- Capture conditions: Verify that filters and permissions did not exclude the relevant packets.
- Visibility boundary: State which interval is bracketed by the observation points and which parts remain unobserved.
These checks turn “the network dropped it” into a more precise finding: for example, a packet was visible at one controlled point and not at another during a defined interval. Naming the exact device or responsible party requires evidence from that part of the path.
Keep the test scoped and repeatable
The commands above are illustrative, not validated against a particular VDS environment. Interface names, installed utility versions, permissions, and supported options vary by Linux distribution and configuration; verify them on the systems being tested. Filter to the relevant host, protocol, and port, and retain captures and timestamps for the symptom window. A route probe can add context, but its missing replies should not be treated as proof that forwarded traffic was lost.
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