Docs TroubleshootingDiagnose Network Connectivity Issues

Diagnose Network Connectivity Issues

Use ping, traceroute, and netstat to diagnose network connectivity problems on your server.

intermediate

8 min read

LightYear Docs Team

Updated April 24, 2026

networkingpingtraceroutenetstattroubleshooting

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Network connectivity issues can manifest as slow responses, packet loss, or complete connection failures. This guide covers the essential diagnostic tools.

Step 1 — Test Basic Connectivity

>_BASH

$ping -c 4 8.8.8.8

OUTPUT

PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=118 time=1.23 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=118 time=1.19 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=118 time=1.21 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=118 time=1.18 ms

--- 8.8.8.8 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 1.18/1.20/1.23/0.018 ms

If ping fails, the issue is at the network level (firewall, routing, or the server's network interface).

Step 2 — Trace the Network Path

>_BASH

$traceroute 8.8.8.8

OUTPUT

traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
 1  gateway (10.0.0.1)  0.456 ms  0.423 ms  0.412 ms
 2  203.0.113.1 (203.0.113.1)  1.234 ms  1.198 ms  1.187 ms
 3  * * *
 4  8.8.8.8 (8.8.8.8)  1.567 ms  1.543 ms  1.521 ms

* * * at a hop means that router does not respond to ICMP — this is normal and not necessarily an error.

Step 3 — Check DNS Resolution

>_BASH

$dig google.com A +short

OUTPUT

142.250.x.x

If DNS fails:

>_BASH

$cat /etc/resolv.conf

OUTPUT

nameserver 8.8.8.8
nameserver 8.8.4.4

If /etc/resolv.conf is empty or missing, add DNS servers:

>_BASH

$echo "nameserver 8.8.8.8" > /etc/resolv.conf
$echo "nameserver 1.1.1.1" >> /etc/resolv.conf

Step 4 — Check Listening Ports

>_BASH

$ss -tulnp

OUTPUT

Netid  State   Recv-Q  Send-Q  Local Address:Port  Peer Address:Port  Process
tcp    LISTEN  0       128     0.0.0.0:22           0.0.0.0:*          sshd
tcp    LISTEN  0       511     0.0.0.0:80           0.0.0.0:*          nginx
tcp    LISTEN  0       511     0.0.0.0:443          0.0.0.0:*          nginx
tcp    LISTEN  0       70      127.0.0.1:3306       0.0.0.0:*          mysqld

Step 5 — Check Active Connections

>_BASH

$ss -tnp | grep ESTABLISHED

Step 6 — Test a Specific Port

>_BASH

$nc -zv YOUR_SERVER_IP 443

OUTPUT

Connection to 45.77.x.x 443 port [tcp/https] succeeded!

Step 7 — Check Bandwidth Usage

>_BASH

$apt install -y nethogs
$nethogs eth0

nethogs shows per-process bandwidth usage in real time, helping identify processes consuming excessive bandwidth.

[!NOTE] If you suspect a DDoS attack, check your LightYear control panel for traffic graphs and consider enabling DDoS protection or using a CDN to absorb traffic.

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