4.4.9 Packet Tracer - Troubleshoot Inter-VLAN Routing – Physical Mode Answers
Topology
Addressing Table
| Device | Interface | IP Address | Subnet Mask | Default Gateway |
|---|---|---|---|---|
| R1 | G0/0/1.3 | 10.3.0.1 | 255.255.255.0 | N/A |
| G0/0/1.4 | 10.4.0.1 | 255.255.255.0 | ||
| G0/0/1.13 | 10.13.0.1 | 255.255.255.0 | ||
| S1 | VLAN 3 | 10.3.0.11 | 255.255.255.0 | 10.3.0.1 |
| S2 | VLAN 3 | 10.3.0.12 | 255.255.255.0 | 10.3.0.1 |
| PC-A | NIC | 10.4.0.50 | 255.255.255.0 | 10.4.0.1 |
| PC-B | NIC | 10.13.0.50 | 255.255.255.0 | 10.13.0.1 |
VLAN Table
| VLAN | Name | Interface Assigned |
|---|---|---|
| 3 | Management | S1: VLAN 3 S2: VLAN 3 |
| 4 | Operations | S1: F0/6 |
| 7 | ParkingLot | S1: F0/2-4, F0/7-24, G0/1-2 S2: F0/2-17, F0/19-24, G0/1-2 |
| 8 | Native | N/A |
| 13 | Maintenance | S2: F0/18 |
Objectives
- Part 1: Evaluate Network Operation
- Part 2: Gather Information, Create an Action Plan, and Implement Corrections
Background / Scenario
All the network devices in this Packet Tracer Physical Mode (PTPM) activity have been preconfigured to include intentional errors that are keeping the inter-VLAN routing from working. Your task is to evaluate the network, identify, and correct the configuration errors to restore full inter-VLAN connectivity. You may find errors with the configurations which are not directly related to inter-VLAN routing. These errors impact the ability of the network devices to perform this function.
Note: The design approach used in this activity is to assess your ability to configure and troubleshoot interVLAN routing only. This design may not reflect networking best practices.
Instructions
Part 1: Evaluate Network Operation
Requirements:
- No VLAN 7 traffic is allowed on the trunks because there are no devices in VLAN 7.
- VLAN 8 is the native VLAN.
- All trunks are static.
- End to end connectivity.
a. Use the laptop computer and appropriate cable to console into the network devices for testing and configuration purposes. The login password on all network devices is “cisco” and the enable password is “class”. You can click and drag the console connection from the console port of one device to another, but you will have to start a new terminal session.
b. Use the ping command to test the following criteria and record the results in the table below.
| From | To | Ping Results |
|---|---|---|
| R1 | S1 VLAN 3 (10.3.0.11) | Unsuccessful |
| S2 VLAN 3 (10.3.0.12) | Unsuccessful | |
| PC-A (10.4.0.50) | Unsuccessful | |
| PC-B (10.13.0.50) | Unsuccessful | |
| S1 | S2 VLAN 3 (10.3.0.12) | Unsuccessful |
| PC-A (10.4.0.50) | Unsuccessful | |
| PC-B (10.13.0.50) | Unsuccessful | |
| S2 | PC-A (10.4.0.50) | Unsuccessful |
| PC-B (10.13.0.50) | Unsuccessful |
Part 2: Gather Information, Create an Action Plan, and Implement Corrections
a. For each requirement that is not met, gather information by examining the running configuration and the routing tables to develop a hypothesis for what is causing the malfunction.
b. Create an action plan that you think will fix the issue. Develop a list of all the commands you intend to issue to fix the issue, and a list of all the commands you need to revert the configuration, should your action plan fail to correct the issue.
Hint: If you need to reset a switchport to default configuration, use the default interface interface name command.
As an example for F0/10:
S1(config)# default interface fastethernet 0/10
c. Execute your action plans one at a time for each criterion that fails and record the fix actions.
R1: Remove the native keyword from G0/0/1.4 and make G0/0/1.8 the native VLAN subinterface.
R1(config)# interface gigabitethernet 0/0/1.4 R1(config-subif)# encapsulation dot1Q 4 R1(config-subif)# ip address 10.4.0.1 255.255.255.0 R1(config-subif)# interface gigabitethernet 0/0/1.8 R1(config-subif)# encapsulation dot1Q 8 native
S1: Reset F0/5 (link to R1) and configure it as a static trunk with native VLAN 8.
S1(config)# default interface fastethernet 0/5 S1(config)# interface fastethernet 0/5 S1(config-if)# switchport mode trunk S1(config-if)# switchport trunk native vlan 8 S1(config-if)# switchport trunk allowed vlan 3,4,8,13
S1: Set native VLAN 8 on F0/1 (link to S2) and allow VLANs 3, 4, 8, and 13.
S1(config)# interface fastethernet 0/1 S1(config-if)# switchport trunk native vlan 8 S1(config-if)# switchport trunk allowed vlan 3,4,8,13
S1: Create VLAN 13.
S1(config)# vlan 13 S1(config-vlan)# name Maintenance
S2: Allow VLANs 3, 4, 8, and 13 on F0/1 (link to S1).
S2(config)# interface fastethernet 0/1 S2(config-if)# switchport trunk allowed vlan 3,4,8,13
Verification:
S1# show interfaces trunk Port Mode Encapsulation Status Native vlan Fa0/1 on 802.1q trunking 8 Fa0/5 on 802.1q trunking 8 Port Vlans allowed on trunk Fa0/1 3-4,8,13 Fa0/5 3-4,8,13 Port Vlans allowed and active in management domain Fa0/1 3,4,8,13 Fa0/5 3,4,8,13 Port Vlans in spanning tree forwarding state and not pruned Fa0/1 3,4,8,13 Fa0/5 3,4,8,13
R1# ping 10.4.0.50 R1# ping 10.13.0.50
Device Running Configuration (Before Fix)
ROUTER R1
!====================================================================
!--- >>> ANNOTATED "BEFORE FIX" RUNNING-CONFIG - ROUTER R1
!--- >>> Lines prefixed "!--- >>>" are annotations added for the troubleshooting
!--- >>> write-up (cross-referenced to the Discrepancy Table) - they are NOT
!--- >>> part of the device's actual output. Everything else below is the
!--- >>> literal "show running-config" capture, unedited.
!====================================================================
R1# show running-config
Building configuration...
Current configuration : 1099 bytes
!
version 15.4
no service timestamps log datetime msec
no service timestamps debug datetime msec
service password-encryption
!
hostname R1
!
!
!
enable secret 5 $1$mERr$9cTjUIEqNGurQiFU.ZeCi1
!
!
!
no ip cef
no ipv6 cef
!
!
!
!
no ip domain-lookup
!
!
spanning-tree mode pvst
!
!
!
interface GigabitEthernet0/0/0
no ip address
duplex auto
speed auto
shutdown
!
interface GigabitEthernet0/0/1
no ip address
duplex auto
speed auto
!
interface GigabitEthernet0/0/1.3
encapsulation dot1Q 3
ip address 10.3.0.1 255.255.255.0
!
interface GigabitEthernet0/0/1.4
encapsulation dot1Q 4 native
ip address 10.4.0.1 255.255.255.0
!--- >>> DISCREPANCY #1 (see Discrepancy Table): the "native" keyword is here,
!--- >>> on the VLAN 4 subinterface. VLAN 8 is the actual native VLAN
!--- >>> configured on both S1 and S2 ("switchport trunk native vlan 8") -
!--- >>> this misplacement breaks return traffic to PC-A.
!
interface GigabitEthernet0/0/1.8
encapsulation dot1Q 8
no ip address
!--- >>> This is where the "native" keyword SHOULD be (dot1Q 8 native) -
!--- >>> it's missing here. See DISCREPANCY #1.
!
interface GigabitEthernet0/0/1.13
encapsulation dot1Q 13
ip address 10.13.0.1 255.255.255.0
!
interface Vlan1
no ip address
shutdown
!
ip classless
!
ip flow-export version 9
!
!
!
banner motd ^C Authorized Users Only! ^C
!
!
!
!
line con 0
password 7 0822455D0A16
logging synchronous
login
!
line aux 0
!
line vty 0 4
password 7 0822455D0A16
login
!
!
!
end
SWITCH S1
!==================================================================== !--- >>> ANNOTATED "BEFORE FIX" RUNNING-CONFIG - SWITCH S1 !--- >>> Lines prefixed "!--- >>>" are annotations added for the troubleshooting !--- >>> write-up (cross-referenced to the Discrepancy Table) - they are NOT !--- >>> part of the device's actual output. Everything else below is the !--- >>> literal "show running-config" capture (terminal paging artifacts like !--- >>> "--More--" have been removed for readability; the embedded CDP !--- >>> syslog message is kept and called out explicitly below). !==================================================================== S1# show running-config Building configuration... Current configuration : 2909 bytes ! version 12.2 no service timestamps log datetime msec no service timestamps debug datetime msec service password-encryption ! hostname S1 ! enable secret 5 $1$mERr$9cTjUIEqNGurQiFU.ZeCi1 ! ! ! no ip domain-lookup ! ! ! spanning-tree mode pvst spanning-tree extend system-id ! interface FastEthernet0/1 switchport trunk allowed vlan 4,8,13 switchport mode trunk !--- >>> DISCREPANCY #3 (see Discrepancy Table): no "switchport trunk native !--- >>> vlan" line at all here (defaults to VLAN 1), and VLAN 3 is missing !--- >>> from the allowed list. This exact mismatch produced the syslog !--- >>> message the device itself logged during this session: !--- >>> %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on !--- >>> FastEthernet0/1 (1), with S2 FastEthernet0/1 (8). ! interface FastEthernet0/2 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/3 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/4 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/5 switchport access vlan 3 switchport mode access !--- >>> DISCREPANCY #2 (see Discrepancy Table): F0/5 is the uplink to R1 !--- >>> per the topology, but it's configured as a plain ACCESS port in !--- >>> VLAN 3 instead of a trunk. This alone blocks VLAN 4/13/8 traffic !--- >>> from ever reaching R1. ! interface FastEthernet0/6 switchport access vlan 4 switchport mode access ! interface FastEthernet0/7 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/8 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/9 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/10 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/11 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/12 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/13 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/14 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/15 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/16 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/17 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/18 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/19 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/20 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/21 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/22 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/23 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/24 switchport access vlan 7 switchport mode access shutdown ! interface GigabitEthernet0/1 switchport access vlan 7 switchport mode access shutdown ! interface GigabitEthernet0/2 switchport access vlan 7 switchport mode access shutdown ! interface Vlan1 no ip address shutdown ! interface Vlan3 ip address 10.3.0.11 255.255.255.0 ! ip default-gateway 10.3.0.1 ! !--- >>> DISCREPANCY #5 (see Discrepancy Table): "show running-config" never !--- >>> displays VLAN database entries (they live in vlan.dat). "show vlan !--- >>> brief" on S1 confirms VLAN 13 does not exist there (only VLANs !--- >>> 1, 3, 4, 7, 8), while S2 has VLAN 13 Maintenance on F0/18. ! banner motd ^C Authorized Users Only! ^C ! ! ! line con 0 password 7 0822455D0A16 logging synchronous login ! line vty 0 4 password 7 0822455D0A16 login line vty 5 15 password 7 0822455D0A16 login ! ! ! ! end
SWITCH S2
!==================================================================== !--- >>> ANNOTATED "BEFORE FIX" RUNNING-CONFIG - SWITCH S2 !--- >>> Lines prefixed "!--- >>>" are annotations added for the troubleshooting !--- >>> write-up (cross-referenced to the Discrepancy Table) - they are NOT !--- >>> part of the device's actual output. Everything else below is the !--- >>> literal "show running-config" capture, unedited. !==================================================================== S2# show running-config Building configuration... Current configuration : 2949 bytes ! version 12.2 no service timestamps log datetime msec no service timestamps debug datetime msec service password-encryption ! hostname S2 ! enable secret 5 $1$mERr$9cTjUIEqNGurQiFU.ZeCi1 ! ! ! no ip domain-lookup ! ! ! spanning-tree mode pvst spanning-tree extend system-id ! interface FastEthernet0/1 switchport trunk native vlan 8 switchport trunk allowed vlan 4,8 switchport mode trunk !--- >>> DISCREPANCY #4 (see Discrepancy Table): native VLAN 8 is already !--- >>> correct here, but the allowed list is missing BOTH VLAN 3 and !--- >>> VLAN 13 (only 4,8 are allowed). Missing VLAN 13 is the most severe !--- >>> part of this: PC-B sits directly on S2, so without it PC-B's !--- >>> traffic can never leave S2 toward S1/R1. ! interface FastEthernet0/2 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/3 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/4 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/5 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/6 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/7 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/8 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/9 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/10 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/11 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/12 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/13 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/14 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/15 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/16 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/17 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/18 switchport access vlan 13 switchport mode access ! interface FastEthernet0/19 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/20 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/21 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/22 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/23 switchport access vlan 7 switchport mode access shutdown ! interface FastEthernet0/24 switchport access vlan 7 switchport mode access shutdown ! interface GigabitEthernet0/1 switchport access vlan 7 switchport mode access shutdown ! interface GigabitEthernet0/2 switchport access vlan 7 switchport mode access shutdown ! interface Vlan1 no ip address shutdown ! interface Vlan3 ip address 10.3.0.12 255.255.255.0 ! ip default-gateway 10.3.0.1 ! banner motd ^C Authorized Users Only! ^C ! ! ! line con 0 password 7 0822455D0A16 logging synchronous login ! line vty 0 4 password 7 0822455D0A16 login line vty 5 15 password 7 0822455D0A16 login ! ! ! ! end
Discrepancy Table
| # | Device | Error | Evidence | Fix |
|---|---|---|---|---|
| 1 | R1 | Native VLAN flag placed on the wrong subinterface — G0/0/1.4 has encapsulation dot1Q 4 native instead of G0/0/1.8 |
Running-config shows encapsulation dot1Q 4 native under G0/0/1.4; both S1 and S2 configure switchport trunk native vlan 8, confirming VLAN 8 is the intended native VLAN, not VLAN 4 |
Under interface gigabitethernet 0/0/1.4, re-enter encapsulation dot1Q 4 (without native) and re-enter ip address 10.4.0.1 255.255.255.0; then apply encapsulation dot1Q 8 native under interface gigabitethernet 0/0/1.8. Only one subinterface per physical port can be native, so remove the flag from .4 first |
| 2 | S1 | F0/5 (uplink to R1) is configured as an access port in VLAN 3 instead of a trunk |
Running-config shows switchport access vlan 3 / switchport mode access under FastEthernet0/5, but the topology requires this link to carry VLAN 3, 4, 8, and 13 to R1's subinterfaces |
default interface fastethernet 0/5 (per the lab's own hint) to clear the leftover access config, then rebuild it as switchport mode trunk, switchport trunk native vlan 8, switchport trunk allowed vlan 3,4,8,13 |
| 3 | S1 | F0/1 (uplink to S2) has no native VLAN set (defaults to VLAN 1) and its allowed-VLAN list is incomplete |
Running-config shows switchport trunk allowed vlan 4,8,13 with no switchport trunk native vlan line; the embedded syslog %CDP-4-NATIVE_VLAN_MISMATCH: ...FastEthernet0/1 (1), with S2 FastEthernet0/1 (8) directly confirms the mismatch |
Add switchport trunk native vlan 8 and change the allowed list to switchport trunk allowed vlan 3,4,8,13 — VLAN 3 is needed for S1/S2/R1 management reachability, VLAN 13 for PC-B's traffic; VLAN 7 stays excluded as required |
| 4 | S2 | F0/1 (uplink to S1) is missing both VLAN 3 and VLAN 13 from the allowed list |
Running-config shows switchport trunk allowed vlan 4,8; native VLAN 8 is already correctly set here (S1 was the side missing it) |
Change the allowed list to switchport trunk allowed vlan 3,4,8,13, matching the corrected S1 side |
| 5 | S1 | VLAN 13 was never created in S1's local VLAN database | show vlan brief on S1 lists VLANs 1, 3, 4, 7, and 8 only; VLAN 13 (Maintenance) exists on S2 but not on S1, so PC-B traffic cannot transit S1 to R1 |
Add vlan 13 / name Maintenance — harmless to re-declare even if it already exists |
Device Configs - Final
ROUTER R1
! ============================================================== !--- 4.4.9 Packet Tracer - Troubleshoot Inter-VLAN Routing - Physical Mode !--- FIX SCRIPT FOR ROUTER R1 !--- Usage: log in to R1 on the console (password "cisco"), type "enable" (password "class"), then paste this whole file at the R1# prompt. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- Troubleshooting lab: only the corrective commands from the Discrepancy Table. ! ============================================================== configure terminal ! -------------------------------------------------------------- !--- Discrepancy #1: the native VLAN flag is on G0/0/1.4 instead of G0/0/1.8. ! -------------------------------------------------------------- !--- Remove "native" from the VLAN 4 subinterface first (only one native subinterface is allowed per port) and re-enter its IP address. interface gigabitethernet 0/0/1.4 encapsulation dot1Q 4 ip address 10.4.0.1 255.255.255.0 exit !--- Make VLAN 8 the native VLAN, matching "switchport trunk native vlan 8" on the switches. interface gigabitethernet 0/0/1.8 encapsulation dot1Q 8 native exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces gigabitethernet 0/0/1.8 -> "Native VLAN" shown for VLAN 8 !--- ping 10.3.0.11 / 10.3.0.12 / 10.4.0.50 / 10.13.0.50 -> successful ! ==============================================================
SWITCH S1
! ============================================================== !--- 4.4.9 Packet Tracer - Troubleshoot Inter-VLAN Routing - Physical Mode !--- FIX SCRIPT FOR SWITCH S1 !--- Usage: log in to S1 on the console (password "cisco"), type "enable" (password "class"), then paste this whole file at the S1# prompt. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- Troubleshooting lab: only the corrective commands from the Discrepancy Table. ! ============================================================== configure terminal ! -------------------------------------------------------------- !--- Discrepancy #2: F0/5 (to R1) is an access port in VLAN 3. ! -------------------------------------------------------------- !--- Reset the port to defaults (lab hint), then build a static trunk with native VLAN 8; VLAN 7 is excluded. default interface fastethernet 0/5 interface fastethernet 0/5 switchport mode trunk switchport trunk native vlan 8 switchport trunk allowed vlan 3,4,8,13 exit ! -------------------------------------------------------------- !--- Discrepancy #3: F0/1 (to S2) has no native VLAN and an incomplete allowed list. ! -------------------------------------------------------------- !--- Native VLAN 8 clears the CDP native VLAN mismatch with S2; VLAN 3 (management) and VLAN 13 (PC-B) are added, VLAN 7 stays excluded. interface fastethernet 0/1 switchport trunk native vlan 8 switchport trunk allowed vlan 3,4,8,13 exit ! -------------------------------------------------------------- !--- Discrepancy #5: VLAN 13 does not exist in the S1 VLAN database (confirmed with show vlan brief). ! -------------------------------------------------------------- !--- PC-B traffic (VLAN 13) must transit S1 to reach R1, so the VLAN must exist here. vlan 13 name Maintenance exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces trunk -> Fa0/1 and Fa0/5 on, trunking, native VLAN 8, VLANs 3,4,8,13 !--- show vlan brief -> VLAN 13 Maintenance present !--- ping 10.3.0.12 / 10.4.0.50 / 10.13.0.50 -> successful ! ==============================================================
SWITCH S2
! ============================================================== !--- 4.4.9 Packet Tracer - Troubleshoot Inter-VLAN Routing - Physical Mode !--- FIX SCRIPT FOR SWITCH S2 !--- Usage: log in to S2 on the console (password "cisco"), type "enable" (password "class"), then paste this whole file at the S2# prompt. Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- Troubleshooting lab: only the corrective commands from the Discrepancy Table. ! ============================================================== configure terminal ! -------------------------------------------------------------- !--- Discrepancy #4: F0/1 (to S1) is missing VLAN 3 and VLAN 13. ! -------------------------------------------------------------- !--- Match the corrected S1 side (adds VLAN 3 management and VLAN 13 PC-B); native VLAN 8 is already set on this port. interface fastethernet 0/1 switchport trunk allowed vlan 3,4,8,13 exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces trunk -> Fa0/1 on, trunking, native VLAN 8, VLANs 3,4,8,13 !--- ping 10.3.0.1 / 10.4.0.50 / 10.13.0.50 -> successful ! ==============================================================
