NHPREP — Hands-On CCNA, CCNP, CCIE Labs & Networking Courses

Lab Objectives

Use the core IOS "show" commands to inspect device configuration, interface state, routing table, and system information.
Learn how to use pipe filters to focus output when troubleshooting.
Apply show-command verification to locate and resolve a simple connectivity problem in the lab topology.

Lab Tasks (Try It Yourself First!)

Complete these tasks WITHOUT looking at the solution below. Use ? and show commands to figure it out.

Task 1: Inspect running configuration on R1 and R2

Find the IP addresses configured on router interfaces for R1 and R2 by examining the running configuration. Record the configured IP on:

R1 GigabitEthernet0/0, Gi0/1, Gi0/2
R2 GigabitEthernet0/0, Gi0/1

Do not change any configuration yet — only read it.

Task 2: Check interface state and counters

On R2, examine the operational state and error counters for the interface connected to the switch (Gi0/1). Confirm the interface is up and there are no CRC or input errors.

Task 3: Verify routing and system info, use pipe filters

On R1, confirm the directly connected routes and that the 10.10.10.0/24, 10.10.20.0/24 and 10.10.30.0/24 networks appear in the routing table.
Use show version to capture the IOS image name and uptime.
Demonstrate use of a pipe filter to quickly extract the IOS image line from show version.

Think About It: When you inspect a router with show ip route, why are directly connected networks listed differently from learned routes (for example, why they appear as “connected” instead of a routing protocol entry)? What practical difference does that make during troubleshooting?

Lab Solution

ASCII Topology (use this exact topology; router interface IPs shown)

                [Internet]
               203.0.113.1
                    |
               R1 (Gateway)
              Gi0/0: 10.10.10.1
              Gi0/1: 10.10.20.1
              Gi0/2: 10.10.30.1
              /     |     \
           R2      R3      R4

Gi0/0: 10.10.10.2 | Gi0/0: 10.10.30.2 Gi0/1: 10.10.40.1 | / \ | S1 S2 S3 / \ | /
PC1 PC2 PC3 PC4 PC5

Note: VLAN subnets used by switches/PCs:

VLAN 10 (Sales) 192.168.1.0/24
VLAN 20 (Engineering) 192.168.2.0/24
VLAN 30 (Management) 192.168.3.0/24

Task 1 Solution: Inspect running configuration on R1 and R2

What we are doing: We read the running configuration to confirm interface IPs. The running config is the active configuration in RAM; this is the authoritative place to see what the router is currently using.

R1# show running-config

What this command does:

show running-config displays the entire active configuration. This matters because it reveals interface IP addresses, routing protocol statements, static routes, and any ACLs—everything currently in use.

Why it matters:

When troubleshooting reachability, the first thing to confirm is that the device has the correct IP addresses and no accidental typos exist in the interfaces.

Verify (expected excerpt):

R1# show running-config
!
version 15.2
hostname R1
!
interface GigabitEthernet0/0
 ip address 10.10.10.1 255.255.255.0
!
interface GigabitEthernet0/1
 ip address 10.10.20.1 255.255.255.0
!
interface GigabitEthernet0/2
 ip address 10.10.30.1 255.255.255.0
!
end

Repeat on R2:

R2# show running-config

Explanation & why:

Running the same on R2 confirms that R2 Gi0/0 and Gi0/1 have the expected addresses for the 10.10.10.0/24 and 10.10.40.0/24 networks.

Verify (expected excerpt):

R2# show running-config
!
hostname R2
!
interface GigabitEthernet0/0
 ip address 10.10.10.2 255.255.255.0
!
interface GigabitEthernet0/1
 ip address 10.10.40.1 255.255.255.0
!
end

Tip: If the running-config is very long, use pipe filters (shown in Task 3) to reduce output to just the interface you need.

Task 2 Solution: Check interface state and counters

What we are doing: We inspect the physical and logical state and error counters of R2 Gi0/1 to ensure it is operational and not experiencing errors.

Commands:

R2# show interfaces GigabitEthernet0/1

What this command does:

show interfaces <interface> provides detailed status (up/down), bandwidth/duplex, packet counters, and error counters. This matters because many connectivity problems are caused by physical layer issues or duplex/speed mismatches.

Why it matters:

A correctly configured IP address is necessary but not sufficient; the interface must be operational and error-free.

Verify (expected excerpt):

R2# show interfaces GigabitEthernet0/1
GigabitEthernet0/1 is up, line protocol is up
  Hardware is Gigabit Ethernet, address is 0001.0001.0001 (bia 0001.0001.0001)
  Internet address is 10.10.40.1/24
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 output errors, 0 collisions, 0 interface resets

Interpretation:

The interface is up/up, full-duplex, 1 Gbps, and there are zero input errors/CRC. If you saw CRC or collisions, that would indicate a cabling, duplex, or physical problem.

Task 3 Solution: Verify routing, show version, and use pipe filters

What we are doing: Confirm the routing table on R1 lists the directly connected networks and show system information (IOS image and uptime). Then demonstrate a pipe to extract the image line.

Commands and explanation:

R1# show ip route

show ip route displays the IPv4 routing table. This tells you which networks are reachable and how they are known (connected, static, or via a routing protocol).

Verify (expected excerpt):

R1# show ip route
Codes: C - connected, S - static, R - RIP, O - OSPF, B - BGP
Gateway of last resort is not set

C    10.10.10.0/24 is directly connected, GigabitEthernet0/0
C    10.10.20.0/24 is directly connected, GigabitEthernet0/1
C    10.10.30.0/24 is directly connected, GigabitEthernet0/2

Why this matters:

Connected routes must be present for the router to forward traffic to those networks. If they're missing, the interface may be administratively down or misconfigured.

Show system version and image:

R1# show version

show version prints platform, IOS image, memory, uptime, and other system facts — crucial when verifying the device is running the expected image and to gather hardware/software info during troubleshooting.

Verify (expected excerpt):

R1# show version
Cisco IOS Software, IOS-XE Software, Version 15.2(4)M
Technical Support: http://www.cisco.com/techsupport
ROM: System Bootstrap, Version 15.0(1r)M
R1 uptime is 2 days, 3 hours, 22 minutes
System returned to ROM by power-on
cisco ISR4451 Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 15.2(4)M, RELEASE SOFTWARE
...
System image file is "bootflash:isr4300-universalk9.15.2.4.SPA.bin"

Using a pipe filter to extract the System image line:

R1# show version | include System image file

The pipe (|) with include filters output to lines matching the argument. This is useful in long outputs to find the exact detail quickly.

Verify (expected output):

R1# show version | include System image file
System image file is "bootflash:isr4300-universalk9.15.2.4.SPA.bin"

Real-world insight: In production, show version is one of the first commands support engineers will ask for; it provides the software and hardware context needed for defect and compatibility analysis.

Troubleshooting Scenario

Scenario: R2 interface to S1 is misconfigured

Symptom: Ping from PC1 (192.168.1.10) to PC3 (192.168.2.10) fails. R1 and R2 appear to have correct configurations at a glance.

Your task: Find and fix the issue so inter-VLAN traffic routes through R2 correctly.

Hint: Use show running-config and show interfaces — look for a mismatched IP on R2 Gi0/1.

Solution:

Inspect R2 running-config and interfaces:

R2# show running-config | section interface GigabitEthernet0/1
R2# show interfaces GigabitEthernet0/1

If you find the IP wrong (for example 10.10.40.2 instead of 10.10.40.1), correct it:

R2# configure terminal
R2(config)# interface GigabitEthernet0/1
R2(config-if)# ip address 10.10.40.1 255.255.255.0
R2(config-if)# no shutdown
R2(config-if)# end

Verify:

R2# show running-config interface GigabitEthernet0/1
R2# show interfaces GigabitEthernet0/1

Explanation:

A wrong IP on R2 Gi0/1 prevents the switch network (10.10.40.0/24) from being reachable. Fixing the IP restores correct adjacency and connected route, allowing forwarding between VLAN subnets via the routers.

Verification Checklist

Confirm interface IPs on R1 and R2 via show running-config.
Interface R2 Gi0/1 is up with 0 errors (show interfaces).
R1 routing table lists connected 10.10.10.0/24, 10.10.20.0/24, 10.10.30.0/24 (show ip route).
Captured IOS image and uptime with show version and used pipe include to extract the image line.

Common Mistakes

Symptom	Cause	Fix
Interface shows administratively down	Interface was shutdown in config	Enter interface and `no shutdown`
Expected connected route not in routing table	IP address misconfigured or interface down	`show running-config` to verify IP, `show interfaces` to verify state; correct IP or bring up interface
`show version` output too long to scan	Not using pipe filters	Use `show version
Seeing CRC/input errors on interface	Bad cable, speed/duplex mismatch	Re-seat cable, check switch port, force correct duplex if mismatch persists

Challenge Task

Configure an ACL on R1 to prevent the 192.168.3.0/24 management VLAN from initiating TCP sessions to 192.168.1.0/24 while allowing all other traffic. Verify with show running-config and show access-lists. (No step-by-step guidance — use what you've learned about reading configs and pipe filters to locate the ACL and test connectivity.)

Show Commands for Troubleshooting

Lab Objectives

Lab Tasks (Try It Yourself First!)

Task 1: Inspect running configuration on R1 and R2

Task 2: Check interface state and counters

Task 3: Verify routing and system info, use pipe filters

Lab Solution

Task 1 Solution: Inspect running configuration on R1 and R2

Task 2 Solution: Check interface state and counters

Task 3 Solution: Verify routing, show version, and use pipe filters

Troubleshooting Scenario

Scenario: R2 interface to S1 is misconfigured

Verification Checklist

Common Mistakes

Challenge Task