This note explains three core networking services that are easy to confuse in practice: DNS, DHCP, and the default gateway. The goal is to understand what each one does so troubleshooting becomes more methodical.
Official AWS network diagram showing how subnet traffic reaches a gateway and leaves the local network boundary, which fits this note better than reusing the broader VPC layout diagram.
Why this matters
these three appear in almost every workstation, server, and homelab networking problem
many people say “the network is down” when only name resolution is broken
security, cloud, and Linux troubleshooting all depend on separating addressing from routing and name resolution
Environment / Scope
Item
Value
Topic
core network services
Best use for this note
separating common network functions
Main focus
address assignment, name resolution, path selection
Safe to practise?
yes
Key concepts
DHCP - automatically gives hosts IP configuration such as address, mask, gateway, and often DNS server
DNS - translates names like github.com into IP addresses
Default gateway - the router a host uses when traffic is leaving the local subnet
Mental model
These three solve different problems:
Need
Service
“Who am I on this network?”
DHCP
“What IP matches this name?”
DNS
“How do I reach something outside my subnet?”
Default gateway
If a host can reach 8.8.8.8 but cannot reach google.com, that usually points more towards DNS than towards routing.
Everyday workflow
Symptom
First thing to check
Host has no IP
DHCP lease or static config
Host can ping IP but not name
DNS
Host can reach local devices but not the internet
default gateway or upstream routing
Host has the wrong address range
DHCP scope or static config
Common misunderstandings
Misunderstanding
Better explanation
”DNS gives me internet access”
DNS only resolves names; routing still has to work
”Gateway is the DNS server”
they can be the same device in a home network, but they are different roles
”DHCP is just the IP address”
DHCP usually provides multiple values, not only the IP
”If a website does not load, DHCP is probably broken”
first separate address, routing, and DNS before guessing
Verification
Check
Expected result
ip addr / ipconfig
host has an expected IP address
ip route / route print
default gateway is present
nslookup example.com or dig example.com
DNS resolution works
ping <gateway>
gateway responds if reachable
Pitfalls / Troubleshooting
Problem
Likely cause
What to check
No network at all
no valid IP config
DHCP lease, static config, interface state
IP works but names do not
DNS problem
DNS server config, nslookup, dig
Local works but internet does not
gateway or upstream routing issue
default route, router health
Wrong network settings keep coming back
DHCP scope issue
DHCP server or reservation
Key takeaways
DHCP, DNS, and the default gateway solve different problems
separating them mentally makes troubleshooting much faster
“network issue” is usually too vague to be useful until you test which layer is failing
