NET-05 · Educational simulation

DHCP & DNS Network Services

A device with no address joins the network. DHCP gives it an address, a gateway and a DNS server; DNS turns a name into an address; only then can it reach the server. Stop either service and watch where the chain breaks.

1DHCP · get an address

2DNS · resolve the name

3Connect to the server

Scenario

DHCP
DNS
TCP · application
Broadcast
Unicast

React Flow

ReadyStep 0 / 27

The client has no IP address (0.0.0.0) and wants to reach server.osanet.local. Press “Start”.

Speed

Explanation

Before you start

The client is plugged into the switch but has no IP configuration at all. Press “Start” to watch it lease an address with DHCP (Discover, Offer, Request, ACK), resolve server.osanet.local with DNS, then connect to the web server — or “Step” to advance one event at a time.

Why is the DHCP Discover a broadcast, sent from 0.0.0.0?
Keep going — the answer unlocks when the run reaches it.
Why does every server receive the Discover?
Keep going — the answer unlocks when the run reaches it.
Is the client configured once the Offer arrives?
Keep going — the answer unlocks when the run reaches it.
Why is the Request broadcast too?
Keep going — the answer unlocks when the run reaches it.
How does the client know which DNS server to ask?
Keep going — the answer unlocks when the run reaches it.
Why does DNS use UDP port 53?
Keep going — the answer unlocks when the run reaches it.
What is an A record?
Keep going — the answer unlocks when the run reaches it.
What do the packets carry — the name or the address?
Keep going — the answer unlocks when the run reaches it.

Message inspector

No message

Protocol: —
Delivery: —
Source IP: —
Destination IP: —
Current device: —
Status: Ready

Protocol layers

Nothing yet

Application—
Service—
Transport—
Network—
Data link—
Physical—

Event timeline

0 / 27

Client initialized--:--:--
DHCP Discover sent--:--:--
Switch flooded the Discover--:--:--
DHCP server received the Discover--:--:--
DHCP Offer sent--:--:--
Switch forwarded the Offer--:--:--
Client received the Offer--:--:--
DHCP Request sent--:--:--
Switch flooded the Request--:--:--
DHCP server received the Request--:--:--
DHCP ACK sent--:--:--
Switch forwarded the ACK--:--:--
DHCP ACK received--:--:--
IP configuration applied--:--:--
Name lookup started--:--:--
DNS Query sent--:--:--
Switch forwarded the query--:--:--
DNS server received the query--:--:--
DNS Response sent--:--:--
Switch forwarded the response--:--:--
Hostname resolved--:--:--
Application request sent--:--:--
Switch forwarded the request--:--:--
Server received the request--:--:--
SYN-ACK sent--:--:--
Switch forwarded the SYN-ACK--:--:--
Connection completed--:--:--

DHCP lease inspector

DHCPINIT

INIT

SELECTING

REQUESTING

BOUND

Offered IP: —
Assigned IP: —
Subnet mask: —
Default gateway: —
DNS server: —
Lease time: —
DHCP server: —
Discovers sent: 0
Lease status: No lease

DNS query inspector

DNSIDLE

IDLE

QUERYING

RESOLVED

Query name: —
Query type: —
Protocol: UDP
Destination port: 53
DNS server: —
Queries sent: 0
Response: —
Response code: —

Application connection

TCP · HTTPIDLE

IDLE

CONNECTING

CONNECTED

Hostname: server.osanet.local
Resolved IP: —
Destination: TCP 80
Client address: 0.0.0.0
Connection: —