Packet Tracer – Troubleshooting Inter-VLAN Routing
Addressing Table
| Device | Interface | IP Address | Subnet Mask | Default Gateway | VLAN |
| R1 | G0/1.10 | 172.17.10.1 | 255.255.255.0 | N/A | VLAN 10 |
| G0/1.30 | 172.17.30.1 | 255.255.255.0 | N/A | VLAN 30 | |
| PC1 | NIC | 172.17.10.10 | 255.255.255.0 | 172.17.10.1 | VLAN 10 |
| PC3 | NIC | 172.17.30.10 | 255.255.255.0 | 172.17.30.1 | VLAN 30 |
Objectives
Part 1: Locate Network Problems
Part 2: Implement the Solution
Part 3: Verify Network Connectivity
Scenario
In this activity, you will troubleshoot connectivity problems caused by improper configurations related to VLANs and inter-VLAN routing.
Part 1: Locate the Network Problems
Examine the network and locate the source of any connectivity issues.
- Test connectivity and use the necessary showcommands on to verify configurations.
- List all of the problems and possible solutions in the Documentation Table.
Documentation Table
| Problems | Solutions |
Part 2: Implement the Solutions
Make changes according to your recommended solutions.
Part 3: Verify Network Connectivity
Verify the PCs can ping other PCs and R1. If not, continue to troubleshoot until the pings are successful.
Suggested Scoring Rubric
Packet Tracer scores 60 points. Completing the Documentation Table is worth 40 points.
The issues common to legacy inter-VLAN routing and router-on-a-stick inter-VLAN routing are also manifested in the context of Layer 3 switching. To troubleshoot Layer 3 switching issues, the following items should be checked for accuracy:
- VLANs – VLANs must be defined across all the switches. VLANs must be enabled on the trunk ports. Ports must be in the right VLANs.
- SVIs – SVI must have the correct IP address or subnet mask. SVI must be up. SVI must match with the VLAN number.
- Routing – Routing must be enabled. Each interface or network should be added to the routing protocol.
- Hosts – Hosts must have the correct IP address or subnet mask. Hosts must have a default gateway associated with an SVI or routed port.
Interface Issues:
When enabling inter-VLAN routing on a router, one of the most common configuration errors is to connect the physical router interface to the wrong switch port. This places the router interface in the incorrect VLAN and prevents it from reaching the other devices within the same subnet.
As shown in the figure, router R1 interface G0/0 is connected to switch S1 port F0/9. Switch port F0/9 is configured for the default VLAN, not VLAN 10. This prevents PC1 from being able to communicate with the router interface. Therefore, it is unable to route to VLAN 30.
To correct this problem, physically connect the router R1 interface G0/0 to switch S1 port F0/4. This puts the router interface in the correct VLAN and allows inter-VLAN routing. Alternately, change the VLAN assignment of switch port F0/9 to VLAN 10. This also allows PC1 to communicate with router R1 interface G0/0.
