Network Services Configuration Cheat Sheet

1️⃣ DNS Server Configuration

Goal: Translate domain names → IP addresses.

1

Assign static IP:

IP: 192.168.10.10
Subnet: 255.255.255.0
Gateway: 192.168.10.1

2

Enable DNS service on the server.

3

Add records:

Hostname	IP Address
www.example.com	192.168.10.50
mail.example.com	192.168.10.20

ip dhcp pool VLAN10
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1
 dns-server 192.168.10.10

PC> ping www.example.com
PC> nslookup www.example.com

Goal: Send/receive emails.

1

Assign static IP:

IP: 192.168.10.20
Subnet: 255.255.255.0
Gateway: 192.168.10.1

2

Enable services:

3

Set domain and users:

Domain: example.com
Users: user1@example.com, user2@example.com

Incoming Server: 192.168.10.20 (POP3)
Outgoing Server: 192.168.10.20 (SMTP)
Username/password: user1/password

Problem	Command / Check
PC cannot resolve DNS	`ping DNS_IP` / `nslookup`
DHCP clients not getting DNS	Check `ip dhcp pool` → `dns-server`
Email not sending	Check SMTP is enabled, check firewall (Packet Tracer: usually off)
Email not receiving	Check POP3 is enabled, client configured correctly

Always use static IP for servers.
Put DNS first, then email.
DHCP can automatically hand out DNS to clients.
If multiple VLANs → use router-on-a-stick + trunk to connect clients to servers.
Test each step before moving to the next.

enable
configure terminal
hostname SW1
no ip domain-lookup

vlan 10
 name USERS
vlan 20
 name SERVERS

interface f0/1
 switchport mode access
 switchport access vlan 10
 no shutdown

interface g0/1
 switchport mode trunk
 switchport trunk allowed vlan 10,20
 no shutdown

interface g0/0.10
 encapsulation dot1Q 10
 ip address 192.168.10.1 255.255.255.0

ip dhcp pool VLAN10
 network 192.168.10.0 255.255.255.0
 default-router 192.168.10.1
 dns-server 8.8.8.8

show vlan brief
show interfaces trunk
show ip interface brief
show running-config
show ip dhcp binding
show ip route

Check for common issues: