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Verification & Troubleshooting Assembly Guide: PTL-0005

Assembly details and expected results for Verifying Directly Connected Networks. It shows the finished configuration, so use it to check your work.

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Lab ID: PTL-0005
Lab Title: Verifying Directly Connected Networks
Category: ip-addressing
Difficulty: Beginner

1. Physical & Packet Tracer Assembly Manifest#

Device Hardware & Module Schedule#

Device Role Device Label Packet Tracer Model Module Slots Software / IOS Version
Routing Gateway R1 Cisco ISR 4321 2x GigabitEthernet onboard (Gi0/0/0, Gi0/0/1) Cisco IOS XE 16.6.4 / IOS 15.x
Accounting Switch S1 Cisco Catalyst 2960-24TT 24x 10/100 FastEthernet, 2x Gigabit Cisco IOS 15.0(2)SE4 (LAN Base)
Engineering Switch S2 Cisco Catalyst 2960-24TT 24x 10/100 FastEthernet, 2x Gigabit Cisco IOS 15.0(2)SE4 (LAN Base)
Accounting Host PC-A PC-PT 1x FastEthernet Generic Host OS
Engineering Host PC-B PC-PT 1x FastEthernet Generic Host OS

Port-to-Port Cabling Matrix#

Origin Device Origin Port Destination Device Destination Port Cable Type Cable Color
R1 GigabitEthernet0/0/0 Switch S1 GigabitEthernet0/2 Copper Straight-Through Solid black
R1 GigabitEthernet0/0/1 Switch S2 GigabitEthernet0/2 Copper Straight-Through Solid black
Switch S1 GigabitEthernet0/1 PC-A FastEthernet0 Copper Straight-Through Solid black
Switch S2 GigabitEthernet0/1 PC-B FastEthernet0 Copper Straight-Through Solid black

Addressing Setup#

  • R1 Gi0/0/0: 192.168.10.1/24, 2001:db8:acad:10::1/64, Link-Local: fe80::1
  • R1 Gi0/0/1: 192.168.20.1/24, 2001:db8:acad:20::1/64, Link-Local: fe80::1
  • S1 (VLAN 1 SVI): 192.168.10.2/24, Gateway: 192.168.10.1
  • S2 (VLAN 1 SVI): 192.168.20.2/24, Gateway: 192.168.20.1
  • PC-A: IPv4: 192.168.10.10/24, Gateway: 192.168.10.1, IPv6: 2001:db8:acad:10::10/64
  • PC-B: IPv4: 192.168.20.10/24, Gateway: 192.168.20.1, IPv6: 2001:db8:acad:20::10/64

2. Intentional Starter State & Troubleshooting Fault Scenarios#

This lab includes intentional preconfigured fault scenarios in the starter topology to teach systematic Layer 3 troubleshooting:

Injected Fault Matrix (Starter Topology)#

Fault ID Component Injected Misconfiguration Observed Symptom Diagnostic Command Remediation Command
FLT-01 R1 Gi0/0/0 Configured with /25 (255.255.255.128) instead of /24 (255.255.255.0) PC-A (.10) can ping R1, but routing table installs 192.168.10.0/25; hosts above .127 unreachable show ip interface brief, show ip route interface Gi0/0/0 -> ip address 192.168.10.1 255.255.255.0
FLT-02 R1 Gi0/0/1 Interface left in administrative shutdown Red link light; interface status shows administratively down; LAN 2 routes missing from routing table show ip interface brief interface Gi0/0/1 -> no shutdown
FLT-03 PC-B Default Gateway misconfigured as 192.168.10.1 (wrong subnet) PC-B cannot communicate outside its local subnet ipconfig on PC-B Set Default Gateway to 192.168.20.1

The fully resolved instructor solution is provided in:

3. Positive Verification Tests#

Test POS-01: Routing Table Inspection of Connected (C) and Local (L) Routes#

  • Action: At R1#, issue show ip route.
  • Expected Terminal Output: 
    R1# show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
...
Gateway of last resort is not set

      192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.10.0/24 is directly connected, GigabitEthernet0/0/0
L        192.168.10.1/32 is directly connected, GigabitEthernet0/0/0
      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, GigabitEthernet0/0/1
L        192.168.20.1/32 is directly connected, GigabitEthernet0/0/1
  • Criterion:
    • C (Connected) routes identify the network address with /24 subnet mask.
    • L (Local) routes identify the router's interface IP address with /32 host mask.

Test POS-02: IPv6 Routing Table Inspection#

  • Action: At R1#, issue show ipv6 route.
  • Expected Terminal Output: 
    R1# show ipv6 route
IPv6 Routing Table - default - 5 entries
...
C   2001:DB8:ACAD:10::/64 [0/0]
     via GigabitEthernet0/0/0, directly connected
L   2001:DB8:ACAD:10::1/128 [0/0]
     via GigabitEthernet0/0/0, receive
C   2001:DB8:ACAD:20::/64 [0/0]
     via GigabitEthernet0/0/1, directly connected
L   2001:DB8:ACAD:20::1/128 [0/0]
     via GigabitEthernet0/0/1, receive
L   FF00::/8 [0/0]
     via Null0, receive
  • Criterion: Connected networks show /64 and local interface host routes show /128.

Test POS-03: End-to-End Inter-LAN Reachability (Post-Remediation)#

  • Action: From PC-A Command Prompt, ping PC-B (192.168.20.10).
  • Expected Terminal Output: 
    C:\> ping 192.168.20.10
Pinging 192.168.20.10 with 32 bytes of data:
Reply from 192.168.20.10: bytes=32 time<1ms TTL=127
Reply from 192.168.20.10: bytes=32 time<1ms TTL=127
Reply from 192.168.20.10: bytes=32 time<1ms TTL=127
Reply from 192.168.20.10: bytes=32 time<1ms TTL=127
  • Criterion: 4/4 replies received with 0% loss.

4. Negative Verification Tests#

  • Action: Issue shutdown on R1 interface GigabitEthernet0/0/0. Immediately view show ip route.
  • Expected Terminal Output: 
    R1(config-if)# shutdown
%LINK-5-CHANGED: Interface GigabitEthernet0/0/0, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/0, changed state to down
R1# show ip route
Gateway of last resort is not set

      192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.20.0/24 is directly connected, GigabitEthernet0/0/1
L        192.168.20.1/32 is directly connected, GigabitEthernet0/0/1
  • Criterion: Connected route 192.168.10.0/24 and local route 192.168.10.1/32 are removed immediately from the routing table when the interface state is down.

Test NEG-02: Traffic to Non-Existent Destination Subnet#

  • Action: From PC-A, attempt to ping an unconfigured network: ping 10.0.0.1.
  • Expected Terminal Output: 
    C:\> ping 10.0.0.1
Reply from 192.168.10.1: Destination host unreachable.
Reply from 192.168.10.1: Destination host unreachable.
  • Criterion: In the absence of a default route (0.0.0.0/0), the router immediately drops packets for unknown subnets and issues ICMP Destination Unreachable.

5. Diagnostic & Troubleshooting Reference#

Diagnostic Command What to Look For Meaning
show ip interface brief Status column administratively down indicates shutdown command was used.
show ip interface brief Protocol column down while Status is up indicates Layer 2 / physical cabling defect or remote port down.
show ip route C routes missing An interface cannot have a connected route in the routing table unless both Status and Protocol are up.
show ip route Subnet mask on C route If subnet mask is /25 instead of /24, verify the subnet mask entered in the ip address command.

This page is generated from labs/ip-addressing/verify-connected-networks/verification.md in the repository. Corrections go there.

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