Internet is not accessible from LAN Switch

[VAbr AVib]

In one of our remote office we have a small LAN with a 3750PoE core and a 3560 client switch. Suddenly the core switch got hanged, the network came back after we did a hard restart of the core switch. After this breakdown, the machines conncted to the core switch is unable to connect to internet addresses, surprisingly all the machines connected to the client switch can still access internet. The core switch has only one default route which is pointing to the firewall. All the LAN addresses are reachable locally as well as through the VPN.

Since the internet works from the client switch and also the VPN is working perfectly fine, therefore we cannot doubt the firewall.

Please let me know if this is an issue with the switch IOS or any configuration.

[Richard Burts · Accepted solution]

It is a very unusual situation for devices connected throgh the client switch to have Internet access while devices connected through the core do not have Internet access. Is it the case that the devices connected through the client switch are in a vlan different from the vlan the core devices are in?

Posting the output of show interface status for the core switch might be a good place to start. It would also be helpful if you post a copy of the config from the core switch (masking out sensitive information such as passwords and public addresses).

HTH

Rick

[VAbr AVib]

You are right Rick, it is an unusual scenario.

Anyway finally we found it was the DNS that was causing the issue.

Thanks a lot for your assistance.

[Richard Burts]

Thank you for posting back to the forum to let us know that you have identified the problem. I am a bit surprised that the problem was with DNS and am glad that you have successfully identified it. And thank you for using the rating system to mark this question as answered.

HTH

Rick