Verification and Diagnostic Guide: PTL-0015

Lab ID: PTL-0015
Lab Title: IPv4 Subnetting and VLSM Network Design
Category: ip-addressing
Simulator Verification: tested_pass

This document details the test procedures, expected outputs, and diagnostic steps required to verify the complete operation of a Variable Length Subnet Masking (VLSM) topology and validate subnet boundaries, point-to-point WAN routing, and IOS error handling.

1. Physical and Logical Topology Verification#

Confirm that all interfaces are active (green link indicators) and correctly assigned:

2. Command-by-Command Verification Matrix#

Test 1: Interface IP Address and Status Check#

On R1:

R1# show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol 
GigabitEthernet0/0/0   192.168.1.1     YES manual up                    up 
GigabitEthernet0/0/1   192.168.1.97    YES manual up                    up

On R2:

R2# show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol 
GigabitEthernet0/0/0   192.168.1.113   YES manual up                    up 
GigabitEthernet0/0/1   192.168.1.98    YES manual up                    up

Test 2: VLSM Routing Table Verification#

Verify the routing table on R1:

R1# show ip route
Gateway of last resort is not set

     192.168.1.0/24 is variably subnetted, 5 subnets, 4 masks
C       192.168.1.0/26 is directly connected, GigabitEthernet0/0/0
L       192.168.1.1/32 is directly connected, GigabitEthernet0/0/0
C       192.168.1.96/30 is directly connected, GigabitEthernet0/0/1
L       192.168.1.97/32 is directly connected, GigabitEthernet0/0/1
S       192.168.1.112/28 [1/0] via 192.168.1.98

• Success Criteria: Note the 4 masks (/26, /30, /32, /28) derived from parent network 192.168.1.0/24.

Verify the routing table on R2:

R2# show ip route
Gateway of last resort is not set

     192.168.1.0/24 is variably subnetted, 5 subnets, 4 masks
S       192.168.1.0/26 [1/0] via 192.168.1.97
C       192.168.1.96/30 is directly connected, GigabitEthernet0/0/1
L       192.168.1.98/32 is directly connected, GigabitEthernet0/0/1
C       192.168.1.112/28 is directly connected, GigabitEthernet0/0/0
L       192.168.1.113/32 is directly connected, GigabitEthernet0/0/0

Test 3: Point-to-Point WAN Transit Ping#

From R1, ping R2:

R1# ping 192.168.1.98
Sending 5, 100-byte ICMP Echos to 192.168.1.98, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms

Test 4: End-to-End Routed Inter-Subnet Host Ping#

From PC-Staff, ping PC-Branch:

C:\>ping 192.168.1.120
Reply from 192.168.1.120: bytes=32 time<1ms TTL=126

• Success Criteria: 0% loss.
• Diagnostic Note: TTL=126 confirms that the packet crossed two routers (R1 and R2).

3. Cisco IOS Subnet Protection Verification#

Test 5: Broadcast Address Assignment Rejection#

Attempt to assign the broadcast address 192.168.1.63/26 to an interface:

R1(config)# interface Loopback99
R1(config-if)# ip address 192.168.1.63 255.255.255.192
Bad mask /26 for address 192.168.1.63

• Analysis: Cisco IOS calculates that host bits are all 1s (192.168.1.00111111) and immediately rejects the assignment.

Test 6: Overlapping Subnet Rejection#

Attempt to configure an overlapping subnet (192.168.1.33/25 overlaps with existing 192.168.1.0/26):

R1(config-if)# ip address 192.168.1.33 255.255.255.128
% 192.168.1.0 overlaps with GigabitEthernet0/0/0

• Analysis: Cisco IOS actively parses existing routing boundaries on all interfaces and prevents illegal route overlapping.

4. Deliverable File Verification#

Ensure all assets exist within the repository:

• assets/starter.pkt: WAN configured, LAN unconfigured.
• assets/completed.pkt: Full VLSM configuration with passing end-to-end ping.
• assets/topology.png: Network topology diagram.
• configs/R1.txt: Router R1 interface and static route configuration.
• configs/R2.txt: Router R2 interface and static route configuration.
• configs/S1.txt: Switch S1 management configuration.
• configs/S2.txt: Switch S2 management configuration.