Networking Problem - Firewall blocking traffic from Ubuntu but allows Windows

Anoop John anoopjohn at
Sat Jun 20 14:49:51 UTC 2009


A group of doctors at a Medical Institution here in Trivandrum
( had decided to move to Ubuntu. Being a Free
Software supporter I had volunteered to set up Ubuntu on their
laptops. I had installed Ubuntu for some of them and some had
installed it on their own but they are now facing a networking problem
which if I don't fix for them might force them to go back to windows.
I had been to the place and tried to troubleshoot the issue twice
without any success so far.

Problem Description:

* When these people try to acess the Wireless network in their office
from Ubuntu, they get connected to the access point but their packets
get stopped at a Symantec firewall that sits at the gateway.


* I can ping the firewall as well as other systems in the network.
* tracepath stops at the firewall.
* The same system when booted off from windows can access the internet
* I tried changing MTU to 1492 and 1400 using NetworkManager but that
didn't help

Network Layout

Wireless connection is via an Accesspoint connected to an L3 switch
(Cisco L3 switch 4507) that forwards all traffic to the
router/firewall (Symantec UTM box 5640) which is connected directly to
the internet. Interestingly the firewall log records that the packets
are being forwarded and not dropped when the connection is from Ubuntu
or Windows.

If you can please direct me as to what is required to solve this issue
I can either go to the institution and try out the directions or Dr.
Biju Soman who is cced here (he works at the institution and is a
passionate Ubuntu supporter) can try out the suggestions and update
the lists with results.

Thank you for your time

Best Regards
Anoop John

"Be the change you wish to see in the world", M. K. Gandhi

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