🟦 Module 1.4 — Configure a Router


1.4.1 Basic Router Settings

🧠 The big picture

Routers are configured very similarly to switches because both use Cisco IOS and similar CLI commands.

A basic router setup should include:

  1. Hostname

  2. Enable secret

  3. Console password

  4. VTY password

  5. Password encryption

  6. MOTD banner

  7. Save configuration

Important commands

enable
configure terminal
hostname R1
enable secret class

line console 0
password cisco
login
exit

line vty 0 4
password cisco
login
exit

service password-encryption

banner motd #Authorized Access Only!#

copy running-config startup-config

The source specifically demonstrates these initial configuration steps and saving the configuration to startup-config.

⭐ HIGH PRIORITY

enable secret

Sets the password used to enter privileged EXEC mode.

line console 0

Configures console access.

line vty 0 4

Configures remote virtual terminal access.

service password-encryption

Encrypts passwords stored in the configuration.

banner motd

Creates a Message of the Day/legal warning banner.

copy running-config startup-config

Saves the current configuration so it survives a reboot.

🧠 Memory trick

Think:

H-P-P-E-B-S

Hostname

Privileged password

Port passwords

Encryption

Banner

Save

1.4.3 Dual-Stack Topology

Dual stack = IPv4 + IPv6 operating on the same router/interface.

A router interface can have both:

IPv4: 192.168.10.1/24
IPv6: 2001:db8:acad:1::1/64

The source uses the dual-stack topology to demonstrate configuring both IPv4 and IPv6 interfaces.

⭐ HIGH PRIORITY

Know that dual stack does NOT mean converting IPv4 into IPv6.

It means:

IPv4 and IPv6 coexist on the same device/network.

1.4.4 Configure Router Interfaces

This is one of the most important sections.

For a router interface to actually work, you need to configure an IP address and activate the interface.

IPv4

interface gigabitethernet 0/0/0
ip address 192.168.10.1 255.255.255.0
no shutdown

IPv6

interface gigabitethernet 0/0/0
ipv6 address 2001:db8:acad:1::1/64
no shutdown

The source identifies the interface requirements as having an IP address and being activated with no shutdown; it also recommends descriptions for troubleshooting.

🚨 HUGE EXAM POINT

Cisco router interfaces are shutdown by default.

So:

no shutdown

= turn interface ON

Whereas:

shutdown

= turn interface OFF

Interface description

description Link to LAN 1

This doesn't make the interface function. It's primarily documentation useful for troubleshooting.

🧠 Remember the basic interface recipe

Interface → IP → Description → No Shutdown

interface g0/0/0
ip address ...
ipv6 address ...
description ...
no shutdown

1.4.6 IPv4 Loopback Interfaces

A loopback interface is a logical/software interface.

It is NOT a physical port.

Example:

interface loopback 0
ip address 10.0.0.1 255.255.255.0

The source describes loopbacks as internal logical interfaces that remain up as long as the router itself is functioning.

⭐ HIGH PRIORITY

Loopbacks are useful for:


  • Testing


  • Management


  • Routing-process testing


  • Simulating additional networks


  • Simulating an Internet connection in labs

🧠 Memory trick

Loopback = fake interface for testing

It's basically a virtual interface that doesn't need a cable.

🚨 Exam trap

Loopback ≠ physical interface.

You cannot plug a cable into:

Loopback0

🟩 Module 1.5 — Verify Connected Networks

This module is heavily focused on SHOW commands.

Think:

Configure → Verify → Troubleshoot

1.5.1 Interface Verification Commands

The big four commands to know:

Command

What it tells you

show ip interface brief

Quick IPv4 interface summary

show ipv6 interface brief

Quick IPv6 interface summary

show running-config interface <interface>

Configuration applied to an interface

show ip route

IPv4 routing table

show ipv6 route

IPv6 routing table

The source specifically identifies these as the primary commands for quickly verifying interface status and routing information.

⭐⭐⭐ VERY HIGH PRIORITY

You should be able to see a command and immediately know what it does.

IPv4 interface summary:

show ip interface brief

IPv6 interface summary:

show ipv6 interface brief

IPv4 routes:

show ip route

IPv6 routes:

show ipv6 route

Specific interface configuration:

show running-config interface g0/0/0

1.5.2 Verify Interface Status

You'll frequently see:

Status    Protocol
up        up

This is good.

⭐⭐⭐ VERY HIGH PRIORITY

Remember:

UP/UP = GOOD

The source explicitly says an interface is active and operational when both Status and Protocol show up.

What if it's not up/up?

You may see:

administratively down/down

This usually means:

Someone forgot no shutdown.

Or:

down/down

This indicates a physical/connectivity problem.

1.5.3 IPv6 Link-Local & Multicast

This is very testable.

An IPv6 interface can have:

Global Unicast

Example:

2001:DB8:ACAD:1::1/64

Link-Local

Example:

FE80::...

⭐⭐⭐ VERY HIGH PRIORITY

Every IPv6-enabled interface must have a link-local address.

Link-local addresses begin with:

FE80::

The source explicitly states that an IPv6 interface requires a link-local address, while a global unicast address is not necessarily required.

Multicast

IPv6 multicast addresses begin with:

FF

The source shows multicast addresses using the FF02 prefix.

🧠 Memory trick

IPv6 address prefixes:

  • FE80 → Link-local

  • 2001 → Global unicast in the examples

  • FF → Multicast

1.5.4 Verify Interface Configuration

Use:

show running-config interface g0/0/0

This shows the commands actually configured on that interface.

For more detailed information:

show interfaces

Shows things such as:


  • Interface information


  • Packet counts


  • Packet flow information


  • Errors/statistics

And:

show ip interface
show ipv6 interface

show IP-specific information.

🚨 Exam trap

Don't confuse:

show running-config interface

with:

show interfaces

running-config → What configuration did I apply?

show interfaces → What's happening with the interface?

1.5.5 Verify Routes

Use:

show ip route

or:

show ipv6 route

⭐⭐⭐ VERY HIGH PRIORITY

Routing table codes:

C = Connected

L = Local

The source explicitly identifies C as directly connected and L as the local route belonging to the router's own interface address.

Example

If R1 has:

192.168.10.1/24

You'll see something similar to:

C 192.168.10.0/24
L 192.168.10.1/32

Meaning:

C → "This entire network is directly connected."

L → "This exact IP belongs to me."

🚨 Important IPv4 vs IPv6 Local Routes

IPv4 local route:

/32

IPv6 local route:

/128

The source explicitly gives these values and notes that local routes have an administrative distance of 0.

🧠 Memory trick

Local = one address

IPv4:

/32

IPv6:

/128

Ping

You can use:

ping <IP address>

to test Layer 3 connectivity.

IPv4:

ping 192.168.10.10

IPv6:

ping 2001:db8:acad:1::10

The source explicitly notes that the IPv6 ping command works the same way as IPv4 except that an IPv6 address is supplied.

1.5.6 Filter Show Command Output

This is another high-priority memorization section.

You can filter show output using:

|

That's the pipe character.

Example:

show running-config | section line vty

The source identifies four filtering parameters.

⭐⭐⭐ Know these four

section

Shows an entire section beginning with the matching expression.

show running-config | section line vty

Think:

section = whole section

include

Shows lines that match your expression.

show ip interface brief | include up

Think:

include = give me matching stuff

exclude

Shows everything that does NOT match your expression.

show ip interface brief | exclude unassigned

Think:

exclude = remove matching stuff

begin

Starts displaying output beginning at the line matching your expression.

show ip route | begin Gateway

Think:

begin = start here

The source demonstrates include, exclude, and begin with these exact types of examples.

🧠 Easy memory trick

S-I-E-B

Section = whole section

Include = matching lines

Exclude = remove matching lines

Begin = start here

1.5.8 Command History

Cisco IOS temporarily stores commands you've entered.

Recall previous commands

Up Arrow / Ctrl+P

→ older commands

Down Arrow / Ctrl+N

→ newer commands

The source specifies these keyboard shortcuts and explains that command history is enabled by default.

View history

show history

Default

10 commands

Increase history

terminal history size 200

This changes the history buffer for the current terminal session.

🎯 Module 1.4–1.5 Exam Priority

🔴 HIGH — Know Cold

  • enable secret

  • line console 0

  • line vty 0 4

  • service password-encryption

  • banner motd

  • copy running-config startup-config


  • Router interfaces are shutdown by default

  • no shutdown


  • IPv4 interface configuration


  • IPv6 interface configuration


  • Loopback = logical/software interface

  • show ip interface brief

  • show ipv6 interface brief

  • show running-config interface

  • show interfaces

  • show ip route

  • show ipv6 route

  • up/up

  • C = Connected

  • L = Local


  • IPv4 local route = /32


  • IPv6 local route = /128


  • IPv6 requires link-local

  • FE80:: = link-local

  • FF = multicast


  • Pipe | = filtering

  • section

  • include

  • exclude

  • begin

🟡 MEDIUM


  • Interface descriptions


  • Dual stack


  • Loopback use cases

  • show ip interface

  • show ipv6 interface

  • ping

  • terminal length

  • terminal history size

🟢 LOW


  • Specific router hardware/interface types


  • Exact example IP addresses


  • Exact example interface names


  • MTU/ICMP/ND output details unless your instructor specifically emphasizes them

🚨 Common CCNA Exam Traps

Trap #1

"The interface has an IP address, so it's active."

❌ Not necessarily.

You still need:

no shutdown

Trap #2

"FE80 is a global IPv6 address."

❌ Nope.

FE80:: = link-local

Trap #3

"C means local."

❌

C = Connected

L = Local

Trap #4

"A local route represents the whole network."

❌

A local route represents the router's specific interface IP.

IPv4 = /32

IPv6 = /128

Trap #5

"show running-config interface tells me everything happening on the interface."

❌

It primarily shows the configuration applied to the interface.

Trap #6

"include means start displaying from here."

❌

That's:

begin

include = only lines that match.

Trap #7

"Loopback is a physical interface."

❌

Loopback = logical/software interface.

🧠 10-Second Mental Map

If you're cramming before a CCNA quiz, think:

ROUTER CONFIG
     ↓
hostname
enable secret
console password
VTY password
encryption
banner
save
     ↓
INTERFACE
     ↓
IP address
IPv6 address
description
no shutdown
     ↓
VERIFY
     ↓
show ip int brief
show ipv6 int brief
show interfaces
show running-config interface
show ip route
show ipv6 route
     ↓
ROUTING TABLE
     ↓
C = Connected
L = Local
     ↓
IPv6
     ↓
FE80 = Link-local
FF = Multicast
     ↓
FILTER
     ↓
| section
| include
| exclude
| begin