Network Connectivity Issue Handling Rules

Purpose

This guide helps you identify and report network connectivity issues with INTROSERV. We cover two key diagnostic tools: MTR testing and iPerf bandwidth measurement. Proper diagnostics speed up our support response and help pinpoint where problems originate.

Before You Start

Check a few basics first:

• Is your local connection stable?
• Have you disabled VPN or proxy?
• Are other apps consuming bandwidth (streaming, downloads)?
• Is your server powered on and reachable?

Tip: If problems persist, move on to MTR and iPerf tests.

MTR Test

What MTR Does

MTR (My Traceroute) shows the network path from your device to a target server. It combines traceroute and ping functionality, giving you real-time latency and packet loss data at each hop.

Use MTR to find:

• Where packets get lost
• Which hops have high latency
• Whether your connection is stable end-to-end

Info: Bidirectional testing required

To get a complete picture of network connectivity, you must run MTR tests in two directions:

• From your computer to the server (outbound direction)
• From the server back to your computer (return direction)

This helps identify whether problems occur on the outbound path, the return path, or both. Network asymmetry is common – one direction may have issues while the other is fine.

Running MTR on Linux

Direction 1: From Your Computer to the Server (Outbound)

sudo mtr -rwz YOUR_SERVER_IP -c 500
sudo mtr -o 'J M X LSR NA B W V' -wzbc 500 YOUR_SERVER_IP

Direction 2: From the Server Back to Your Computer (Return)

Log into your INTROSERV server via SSH and run:

Tip: For best results, perform the MTR test in rescue mode. This eliminates any interference from the server's operating system or applications.

sudo mtr -rwz YOUR_LOCAL_IP -c 500
sudo mtr -o 'J M X LSR NA B W V' -wzbc 500 YOUR_LOCAL_IP

Replace YOUR_SERVER_IP with your INTROSERV server IP and YOUR_LOCAL_IP with your public IP address (find it by running curl ifconfig.me on your computer before connecting to the server).

Info: Execution takes some time – wait for it to complete. The -c 500 flag sends 500 packets for reliable results.

Additional Linux Diagnostics

Before submitting a support ticket, gather NIC (network interface) information:

Define your default NIC name:

ip route | grep default

The NIC name appears after the word "dev" (e.g., eth0, ens3).

Check for NIC errors:

date && sudo ethtool -S ethX | grep error

Check connection speed:

date && sudo ethtool ethX | grep Speed

Replace ethX with your actual NIC name from the ip route | grep default command.

Identify active interface and IP:

ip a

Verify the gateway:

ip a

What to look for: The ethtool error check should return zeros or empty output. Any non-zero values indicate hardware or cable issues that should be reported to support. Include the Speed output to confirm your interface is operating at the expected rate.

Running MTR on Windows

For MTR testing on Windows, use WinMTR – a graphical version of MTR. Download and run it following this guide: Checking the WinMTR Channel

Run tests in both directions:

• From your computer to the server
• From the server to your computer (for Windows servers, connect via RDP and run WinMTR on the server side)

Take screenshots of your WinMTR results to attach to your support ticket.

Additional Windows Server Diagnostics

Open PowerShell as Administrator and run these commands:

Define IP, NIC status and name:

Get-NetAdapter | Select-Object Name, Status, LinkSpeed

Check for NIC errors:

Get-NetAdapterStatistics -Name "SERVERS_ACTIVE_NIC" | Select-Object *Error*, *Discard* | Format-List

Replace SERVERS_ACTIVE_NIC with the NIC name from the previous command (e.g., "Ethernet", "Public Network").

Verify the gateway:

Get-NetRoute -DestinationPrefix "0.0.0.0/0"

The NextHop value is your default gateway.

What to look for in NIC statistics? Any non-zero values should be reported to support:

• ReceivedPacketErrors – errors during reception (usually cable or port issues)
• OutboundPacketErrors – errors during transmission
• ReceivedPacketsDiscarded – dropped packets (indicates congestion)

Reading MTR Output

What the Results Tell You

• Packet loss: Any loss (>0%) may suggest an issue. However, some packet loss is normal on certain hops – some routers have ICMP disabled or rate-limited, showing as loss in MTR while traffic still flows normally. These hops are often configured this way intentionally and don't indicate a real problem. Check where packet loss occurs in both directions. If loss happens before INTROSERV hops (in Direction 1) or after your IP (in Direction 2), your ISP is the issue. If consistent loss appears on multiple INTROSERV hops or affects your actual service, we need to investigate. In any case, send the results of your bidirectional test to our support team for analysis.
• Latency: Some increase is normal as packets travel further. Slight jumps between hops are expected. Watch for sudden spikes or very high variance (StDev), which indicate instability or congestion. Compare results between both directions – asymmetry may reveal the source of the problem.

Baseline values

For EU regions, expect 10–50ms latency to Europe and 100–300ms to other continents. Compare your results against these ranges in both directions.

When you report issues, always attach both MTR reports (to-server and from-server) or screenshots, plus the NIC diagnostic output. Bidirectional reports are required – a one-way test alone is not enough for proper diagnosis.

Add additional information if possible:

• YOUR_LOCAL_IP: IP address of your PC or server outside INTROSERV
• Public MAC address of the source PC, server
• Public MAC address of your server within INTROSERV
• Protocol type involved (TCP or UDP): ?
• Problem direction: YOUR_LOCAL_IP to YOUR_SERVER_IP, vice versa, or both?
• Specific frequency: permanent or intermittent?

iPerf Bandwidth Testing

iPerf is a network performance measurement tool that accurately tests bandwidth between your server and public test servers. For INTROSERV diagnostics, we recommend using public iPerf servers geographically close to your data center location, providing reliable results that reflect your actual service quality.

Why Not Speedtest-cli or Browser Tests?

We do not recommend using Speedtest-cli, Speedtest.net, or Fast.com for diagnostics. These services randomly select test servers on third-party networks, which can produce inconsistent results. A weak or congested server on their infrastructure may show poor speeds that don't reflect your actual connection quality to INTROSERV. This leads to false reports of service issues.

Instead, we recommend using public iPerf servers geographically close to your data center for accurate bandwidth measurement.

Installing iPerf and Running Tests On Linux:

sudo apt install iperf3

iPerf3 supports two test directions:

Upload test:

iperf3 -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -i 0

This measures upload speed – check the Sender value in results.

Download test:

iperf3 -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -R -i 0

This measures download speed – check the Receiver value in results. The -R flag reverses the test direction.

Save the results to a file if needed:

iperf3 -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -i 0 > iperf-upload.txt

iperf3 -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -R -i 0 > iperf-download.txt

Installing iPerf and Running Tests On Windows / Windows Server:

1. Download iperf3 for Windows from: https://iperf.fr/iperf-download.php
2. Extract the downloaded ZIP file to a folder, e.g., C:\iperf3.
3. Open Command Prompt (cmd.exe) and navigate to the folder: cd C:\iperf3
4. Run tests in both directions:

Upload test (outbound):

iperf3.exe -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -i 0

This measures upload speed – check the Sender value in results.

Download test (inbound):

iperf3.exe -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -R -i 0

This measures download speed – check the Receiver value in results. The -R flag reverses the test direction.

Save the results to files if needed:

iperf3.exe -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -i 0 > iperf-upload.txt

iperf3.exe -c <public_iperf_server_ip> -p <port> -t 30 -P 10 -R -i 0 > iperf-download.txt

Command parameters explained:

• -c <IP> – connect to server at this IP address
• -p <port> – use specified port or port range
• -t 30 – run test for 30 seconds
• -P 10 – use 10 parallel connections (tests full bandwidth capacity)
• -i 0 – disable interval reports (show only final results)
• -R – reverse test direction (public iperf server sends to you, measures download speed)

Tip: Choose a test server geographically close to your INTROSERV data center. Testing from a Germany-based server using an Australian iPerf server may give inaccurate results. These are public servers and may occasionally be busy – if one doesn't respond, run the test again after a short while.

Understanding iPerf Output

In iPerf, the sender line shows the upload speed from your test source to the target server, while the receiver line shows the download speed back from the server to your device.

For consistent measurements, note both values and repeat the test at least three times.

Getting Accurate Results

Run at least three consecutive tests to catch intermittent problems. Before testing:

• Close bandwidth-heavy apps (streaming, downloads, file transfers)
• Don't run tests on multiple devices simultaneously
• Ensure no background updates are running

Save your results with timestamps (in UTC) and the test server location. A screenshot of the final output is also acceptable.

Expected Performance

After the test completes (wait for full 30 seconds), you'll see final results like:

Info: Wait for the test to complete fully. The final summary appears at the end after all interval output. Screenshot or save only the final [SUM] lines – these contain your actual results.

For EU service, download/upload speeds shouldn't drop more than 10–15% below your plan limits during off-peak hours. If you see worse, something's wrong.

iPerf Public Test Servers

To get accurate results, use a public iPerf server geographically close to your INTROSERV data center location. Below are recommended public iPerf servers with reliable 10Gbps+ uplinks.

Europe:

Germany, Wolfsburg

# Upload test (check Sender value):
iperf3 -c 62.176.224.217 -p 5201 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 62.176.224.217 -p 5201 -t 30 -P 10 -R -i 0

Netherlands, Naaldwijk

# Upload test (check Sender value):
iperf3 -c 185.182.195.76 -p 5201 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 185.182.195.76 -p 5201 -t 30 -P 10 -R -i 0

United Kingdom, London

# Upload test (check Sender value):
iperf3 -c 5.180.211.133 -p 5200 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 5.180.211.133 -p 5200 -t 30 -P 10 -R -i 0

France, Paris

# Upload test (check Sender value):
iperf3 -c 45.147.210.189 -p 5200-5240 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 45.147.210.189 -p 5200-5240 -t 30 -P 10 -R -i 0

Poland, Warsaw

# Upload test (check Sender value):
iperf3 -c 185.246.208.67 -p 5201 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 185.246.208.67 -p 5201 -t 30 -P 10 -R -i 0

North America:

USA, New York

# Upload test (check Sender value):
iperf3 -c 194.33.45.192 -p 5200 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 194.33.45.192 -p 5200 -t 30 -P 10 -R -i 0

USA, Los Angeles

# Upload test (check Sender value):
iperf3 -c 77.247.126.223 -p 5200-5209 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 77.247.126.223 -p 5200-5209 -t 30 -P 10 -R -i 0

Canada, Montreal

# Upload test (check Sender value):
iperf3 -c 70.38.95.143 -p 5201-5210 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 70.38.95.143 -p 5201-5210 -t 30 -P 10 -R -i 0

Asia-Pacific:

Singapore

# Upload test (check Sender value):
iperf3 -c 23.108.99.54 -p 5201-5210 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 23.108.99.54 -p 5201-5210 -t 30 -P 10 -R -i 0

Australia, Sydney

# Upload test (check Sender value):
iperf3 -c 23.106.244.70 -p 5201-5210 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 23.106.244.70 -p 5201-5210 -t 30 -P 10 -R -i 0

India, Bangalore

# Upload test (check Sender value):
iperf3 -c 49.205.75.2 -p 5001-5020 -t 30 -P 10 -i 0
# Download test (check Receiver value):
iperf3 -c 49.205.75.2 -p 5001-5020 -t 30 -P 10 -R -i 0

Common Issues

• ISP issues: If MTR shows loss on hops before INTROSERV infrastructure, contact your ISP.
• External networks: Please note that INTROSERV is responsible for connectivity within its data centers and backbone infrastructure. If packet loss or latency occurs outside INTROSERV's network – for example, on ISP or intermediate carrier routes – these are beyond our control and responsibility.
• Maintenance: If any maintenance or detected network issues occur, INTROSERV provides notifications through official communication channels. We always strive to inform clients in advance or as soon as possible.

Reporting to INTROSERV Support

Include this information:

• Your server IP or hostname
• Bidirectional MTR reports (both directions attached)
• NIC diagnostic output (ethtool/PowerShell results)
• iPerf test results to public iPerf server close to your data center location
• When you noticed the problem (UTC time)
• Whether it's happening constantly or on and off
• Your location and ISP name (if relevant)

Example Ticket

Subject: Network issue - Germany DC Server IP: 185.XX.XX.XX

Bidirectional MTR Reports: [mtr-report-to-server.txt attached] [mtr-report-from-server.txt attached]

NIC Diagnostics: [ethtool output or PowerShell results attached/pasted]

Info: Alternatively, you can include screenshots of the MTR results below or attach them to the ticket.

iPerf Tests to iPerf server in Germany (62.176.224.217) – tested at 14:30–14:35 UTC

UPLOAD TESTS – check Sender value:

iperf3 -c 62.176.224.217 -p 5201 -t 30 -P 10 -i 0

Test (14:30 UTC): Result: 1.95 Gbits/sec

Retest (14:31 UTC): Result: 1.90 Gbits/sec

DOWNLOAD TESTS – check Receiver value:

iperf3 -c 62.176.224.217 -p 5201 -t 30 -P 10 -R -i 0

Test (14:33 UTC): Result: 1.87 Gbits/sec

Retest (14:34 UTC): Result: 1.88 Gbits/sec

Summary: Upload average: ~1.92 Gbits/sec Download average: ~1.88 Gbits/sec

Problem: High latency to server Started: 2025-01-15 at 14:30 UTC Ongoing?: Yes (tested over 30 minutes) Location: Stockholm, Sweden (ISP: Telia)

Useful Commands Reference

sudo mtr -o 'J M X LSR NA B W V' -wzbc 500 <host>

ip route | grep default

sudo ethtool -S ethX | grep error

sudo ethtool ethX | grep Speed

ip a

ip r

iperf3 -c <server_ip> -p <port> -t 30 -P 10 -i 0

iperf3 -c <server_ip> -p <port> -t 30 -P 10 -R -i 0

ping <host>

traceroute <host>

curl ifconfig.me