If you're able to ping devices within the same VLAN but not across different VLANs, and the devices are successfully obtaining IP addresses via DHCP, the issue likely lies in the inter-VLAN routing or the access control lists (ACLs) on your network devices. Here are some steps to troubleshoot:
Check Inter-VLAN Routing: Ensure that your Layer 3 switch is correctly configured for inter-VLAN routing. This usually involves setting up Virtual LAN interfaces (SVIs) for each VLAN and enabling routing.
Inspect VLAN Configuration: Verify that the VLANs are correctly defined and that the ports are assigned to the appropriate VLANs.
Review Access Control Lists (ACLs): Check if there are any ACLs that might be blocking traffic between VLANs. Sometimes, ACLs are set up to restrict traffic for security reasons, and they might be too restrictive.
Examine Subnetting and Gateway Settings: Ensure that the subnetting is correctly done and that the devices have the correct default gateway settings. The gateway should typically be the IP address of the Layer 3 switch’s VLAN interface.
Firewall/Security Settings: If there are firewalls or other security appliances in the network, check their configurations to ensure they are not blocking the ICMP packets used for pinging.
Physical Connectivity and Duplex Mismatch: Confirm that there are no physical connectivity issues or duplex mismatches on the network interfaces.
Software and Firmware Updates: Ensure that the network devices are running the latest software and firmware versions, as bugs in older versions might cause such issues.
If after these checks the issue persists, it might be helpful to capture and analyze network traffic on the switch or use network troubleshooting tools to further diagnose the problem.
