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Linux networking problem

Last response: in Linux/Free BSD
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May 27, 2011 2:50:49 AM

Hi everyone,
I have Ubuntu 8.04 running virtualmin email server for my small company. I have two 24 port gigabit switches, one of the switch is a "smart switch" (so I can configure it from its web interface, though I havent, it is running out of the box).
The weird problem i'm having is that, if I restart my ubuntu box, it gets IP from router (pfsense) but it cant connect to the internet, nor can it ping anyone else on the network except router. I have to reboot both switches for the ubuntu to connect to the internet , I don't have this problem with any of my windows boxes. BTW, the ubuntu box is plugged into regular switch not in the smart switch.

Can anyone please help?

Thank you
Anonymous
May 27, 2011 10:57:04 AM

This topic has been moved from the section Networking to section Linux/Free BSD by Grumpy9117
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May 27, 2011 3:23:23 PM

whats ifconfig have to say about the connection? if that fails to provide useful information check your logs (on server and client), and specifically the daemon log should provide information on your dhcp service.
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May 28, 2011 5:55:28 AM

I agree with skittle, post the contents of ifconfig for the interface. Is the Ubuntu machine getting a standard dhcp lease as expected from the router (pfsense)?
One thing I like to do when having issues like this is open two terminal windows, in one terminal run
sudo tcpdump -vv -i <interface> | grep <your computers ip address>

then in the other terminal window
sudo dhclient


and watch to see what exactly is going on when your computer is requesting the address. The -vv switch used in the tcpdump command will show you the entire conversation in detail.

But if everything works when you reboot the switch, that might be a different issue all together. Seems odd that only Ubuntu would have a issue. What model/make of switch are you using?
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May 28, 2011 2:08:46 PM

Richie086 said:
I agree with skittle, post the contents of ifconfig for the interface. Is the Ubuntu machine getting a standard dhcp lease as expected from the router (pfsense)?
One thing I like to do when having issues like this is open two terminal windows, in one terminal run
sudo tcpdump -vv -i <interface> | grep <your computers ip address>

then in the other terminal window
sudo dhclient


and watch to see what exactly is going on when your computer is requesting the address. The -vv switch used in the tcpdump command will show you the entire conversation in detail.

But if everything works when you reboot the switch, that might be a different issue all together. Seems odd that only Ubuntu would have a issue. What model/make of switch are you using?


Please see the pictures,
1.

2.

3.

4.
This is how my switches are connected.

I had just downloaded and installed some updates from update manager, and it restarted my networking and now i cant connect to the internet or network, however the machine does have IP. So I opened the terminal and ran the commands you had posted the results are in picture below.

You are right it may not just be the Ubuntu machine, yesterday when i plugged in my HP vista laptop in the switch it had obtained IP but i could not connect to network or internet unless power off and then on the switches.

The switches I have are ZyXEL GS-1124A and SMC GS24C-Smart. I dont know whats going on, it never used to be like this, it was working fine for a year.
Could it be my router thats the problem? It had recently crashed so I had to rebuild it.

Any help will be appreciated

Thank you
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May 28, 2011 4:46:07 PM

So, the tcpdump window did not output anything at all? that seems strange.

And you are now having this same issue on a hp laptop? hmmmm.. Do you have any options configured in pfsense for your dhcp server other than the normal stuff? How recently did you rebuild your router? Did this issue start to happen around the same time you rebuilt the router? Is the PFSense router ALSO your primary gateway? I am assuming it is. Do you have a static or dynamic external ip address? My only exp with dsl was over 10 years ago when I had PacBell as my ISP. It was also the only non-business class ISP account ive seen that used static addresses for everything. They allocated a block of 5 static ips and each machine had its own external ip address! It's crazy to think of how carelessly ISPs were handing out ipv4 address space back then.

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May 28, 2011 5:08:33 PM

Richie086 said:
So, the tcpdump window did not output anything at all? that seems strange.

And you are now having this same issue on a hp laptop? hmmmm.. Do you have any options configured in pfsense for your dhcp server other than the normal stuff? How recently did you rebuild your router? Did this issue start to happen around the same time you rebuilt the router? Is the PFSense router ALSO your primary gateway? I am assuming it is. Do you have a static or dynamic external ip address? My only exp with dsl was over 10 years ago when I had PacBell as my ISP. It was also the only non-business class ISP account ive seen that used static addresses for everything. They allocated a block of 5 static ips and each machine had its own external ip address! It's crazy to think of how carelessly ISPs were handing out ipv4 address space back then.


DHCP is configured with regular stuff, I have a static external IP and I did start to experience the problems around the same time my router crashed and i had to rebuild.
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