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Cisco Wireless can ping but cannot browse Internet

psychic_zero used Ask the Experts™
Dear Expert,

My organization have purchased Cisco 4400 Series Wireless LAN Controller and  9 unit of Cisco Aironet 1240 AG Series on year 2008. There is no major problem since we're start using this product until last week. We're now facing problem whereby any computer that connected to this wireless device cannot browse to the internet.

We can ping to any web server and also telnet/ssh to the server, but cannot open any website through Internet Browser. We also can ping using URL eg. www.google.com which means the DNS is working fine but still cannot browse it. We don't think it is Firewall problem because
we also cannot browse to our Internal Website which don't have a firewall between them.

Please help us to solve this problem.
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Does your organization use any proxy servers?
Jackie Man IT Manager
Top Expert 2010
Have you tried to power off the  Cisco 4400 Series  Wireless LAN Controller and power on it again after a few minutes?


maximus5328: I don't have proxy server. If using wired connection the computer can browse to Internet.

jackieman: I've tried reboot the Cisco Wireless controller many times but still the same.
How many computers refuse to browse AND can ping to the same URL?


fmarshall: All PC, even if only 1 PC which connected to the wireless refuse to browse the Internet but can ping to the URL.
Jackie Man IT Manager
Top Expert 2010

It can be hardware problem of Cisco Wireless controller.

Can you login the console of Cisco Wireless controller via wired computer?
;;;;Is the Cisco firmware up to date?


jackieman: Yes I can login to the console via wired computer using web admin or telnet.

fmarshall: I'm not sure the firmware is up to date, mine is version But before it's working like charm.
You shoud check on WLC what interface (should be ap-manager) is commited to which VLAN (if any) and be shure what IP address set is delivered to wireless clients.

Next be shure what data clients are getting form DHCP server.

Last check ACL on router (or device which is doing the traffic filtering) regarding this IP address set. Check all ACL's for this IP set . You will deffinetly fidn the line which is bothering you.

If not post listing of configurations for WLC, router, AP's and provide some shema of your Network.



It is due build in IPS installed in the switches. After disable the IPS the wireless network can work as usual.