This note gives a simple first-pass workflow for checking whether a host has basic network connectivity. It is meant as a calm starting point before diving into deeper troubleshooting.
Why this matters
basic checks often solve or narrow the issue quickly
they stop troubleshooting from turning into random guessing
the same pattern is useful in Linux, Windows, servers, homelab, and cloud labs
Environment / Scope
Item
Value
Topic
first-pass network troubleshooting
Best use for this note
workstation, VM, or server connectivity checks
Main focus
interface, IP, gateway, DNS
Safe to practise?
yes
Key concepts
start local before testing remote systems
separate IP connectivity from DNS resolution
verify what the host believes before blaming the network
Steps / Workflow
1. Check interface state
Confirm the interface is up and has an address.
ip addr
2. Check the route and default gateway
ip route
3. Test the local gateway
ping <gateway-ip>
4. Test external IP connectivity
ping 8.8.8.8
5. Test DNS resolution
nslookup github.com
or:
dig github.com
Commands / Examples
Command
Purpose
ip addr
show interface addresses
ip route
show route table and default gateway
ping <gateway-ip>
test local path to the gateway
ping 8.8.8.8
test external IP reachability
nslookup github.com
test basic DNS resolution
Verification
Check
Expected result
Interface check
interface is up and has expected IP config
Gateway test
gateway replies if reachable
External IP test
external IP is reachable if routing works
DNS test
name resolves to an IP address
Pitfalls / Troubleshooting
Problem
Likely cause
What to check
No IP address
DHCP failure or interface issue
interface state, DHCP lease
Gateway ping fails
local network issue or wrong gateway
route table, VLAN, cable, Wi-Fi
IP works but names fail
DNS issue
DNS server settings
DNS works but app still fails
service-specific issue
ports, firewall, app health
Key takeaways
check local interface state before testing the internet
separate IP reachability from DNS resolution
use a repeatable sequence so troubleshooting stays calm and fast