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Ubuntu Network Proxy isn't working correctly


I have an Ubuntu 11.04 machine that i am having problems connecting to the internet with.  Our network uses a proxy server and i have added a system wide proxy, with Authentication, into Ubuntu but i still can't access the internet.

Firefox is configured to use the system proxy but can't access the internet.  If i type an address in manually it says "Level 15 access required"

If i change firefox to input the proxy address manually, and then connect to the net it asks for my proxy credentials and lets me on the internet fine.

Am i missing something?  This is the second Ubuntu machine i have made and the first one worked fine with a system wide Network Proxy, just not this one.

I've attached screenshots for you to look at

LinuxLinux Security

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8/22/2022 - Mon

Is your 2nd Ubuntu machine on the same subnet as the 1st one?  Some proxy servers actually filter source IPs.  If you're not on the trusted IP list, it needs password to let the traffic through.  If your IPs from the machines are private (non route-able), please post them so we can check.

I'm suspecting that other applications on the machine can't access Internet either, not just Firefox?

The second Ubuntu is on the same subnet as the first one.

It originally was configured with a static IP address of and its now been configured as

When it was on it didn't require a proxy as that address is confgured to bypass the proxy.  However on the new address it does need a proxy and its from that point onwards i can't access the internet.

The 1st Ubuntu machine was always on an IP address that required a proxy, and when I put the network proxy in teh settings it worked fine

Any ideas?
I started with Experts Exchange in 2004 and it's been a mainstay of my professional computing life since. It helped me launch a career as a programmer / Oracle data analyst
William Peck

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