Why this is next
Right now:
- You manually configured IPs ❌
- That does not scale ❌
CCNA expects you to know:
- DHCP concepts
- DHCP pools
- DHCP per VLAN
- Default gateway via DHCP
🧠 What we are about to do (concept only)
We will:
- Turn HO-R1 into a DHCP server
- Create one DHCP pool per VLAN
- Let PCs get IPs automatically
⚠️ This is core CCNA.
🔹 VLAN → DHCP mapping (LOCK THIS IN)
| VLAN | Subnet | Gateway | DHCP Pool |
|---|---|---|---|
| 10 | 10.10.10.0/24 | 10.10.10.1 | USERS |
| 20 | 10.10.20.0/24 | 10.10.20.1 | SERVERS |
| 30 | 10.10.30.0/24 | 10.10.30.1 | WIFI |
🚫 BEFORE WE CONFIGURE (VERY IMPORTANT)
Do NOT configure DHCP yet.
First answer this (quick check):
👉 Who should provide DHCP in this lab?
- Router (HO-R1)?
- Server (later)?
Correct CCNA order:
➡️ Router first, server later (so you understand both).
STEP 28 — DHCP on Router (HO-R1)
Goal
- Automatically assign IP addresses
- One DHCP pool per VLAN
- PCs should no longer need manual IP config
🧠 First: how DHCP works (VERY short)
DORA (remember this for CCNA):
- Discover – PC asks for IP
- Offer – DHCP server offers IP
- Request – PC accepts
- Acknowledge – DHCP server confirms
In our lab:
- HO-R1 = DHCP server
- VLAN gateways already exist (ROAS)
🔹 STEP 28.1 — Exclude gateway IPs (IMPORTANT)
We must stop DHCP from giving out gateway IPs.
On HO-R1:
enable
configure terminal
ip dhcp excluded-address 10.10.10.1
ip dhcp excluded-address 10.10.20.1
ip dhcp excluded-address 10.10.30.1
(Optionally you can exclude more later, e.g. .1–.10)
🔹 STEP 28.2 — DHCP pool for VLAN 10 (USERS)
ip dhcp pool USERS
network 10.10.10.0 255.255.255.0
default-router 10.10.10.1
dns-server 8.8.8.8
🔹 STEP 28.3 — DHCP pool for VLAN 20 (SERVERS)
ip dhcp pool SERVERS
network 10.10.20.0 255.255.255.0
default-router 10.10.20.1
dns-server 8.8.8.8
🔹 STEP 28.4 — DHCP pool for VLAN 30 (WIFI)
ip dhcp pool WIFI
network 10.10.30.0 255.255.255.0
default-router 10.10.30.1
dns-server 8.8.8.8
end
write memory
🔹 STEP 28.5 — Test DHCP (VERY IMPORTANT)
On each PC / device:
- Go to IP Configuration
- Select DHCP
- Wait a few seconds
You should see:
- IP address in correct subnet
- Correct default gateway
- DNS populated
🔹 STEP 28.6 — Verify on router
On HO-R1:
show ip dhcp binding
You should see leased IPs.
Optional:
show ip dhcp pool
🧠 What you just learned (CCNA EXAM CORE)
- DHCP server configuration
- DHCP exclusions
- DHCP per VLAN
- Role of default gateway
- Router as DHCP server
This is guaranteed CCNA content.
🚫 Common CCNA mistakes (you avoided)
❌ Forgetting exclusions
❌ Wrong default-router
❌ DHCP pool subnet mismatch
❌ Expecting DHCP to work without ROAS
One sentence to lock it in
Each VLAN needs its own DHCP pool with the correct gateway IP.
