Question

DNS Server lost after NAC Upgrade to 6.1.X


Userlevel 3
After I upgraded a few NAC Appliances from 5.X to 6.1.X or from 6.1.X to latest 6.1.182 I had sometimes the problem that NAC lost its DNS Server information in the /etc/resolvresolv.conf.

After dnetconfig (without changing something) all worked fine again.

Does anybody know a reason for that? It doen't happen on every appliance.

Best Regards
Michael

10 replies

Userlevel 2
No, I did not have any problems with it. I upgraded 6 NAC Gatways at one customer from 6.0 to 6.1 and it works fine. Last week I updated from 4.3 to 6.1 with 2 NAC GW's and it works also fine.
Userlevel 6
I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.
Userlevel 6
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

I got around to filing 01124098 on this.
Userlevel 3
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

Great - but I just don't get what you mean 😉
Userlevel 6
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

Well, do your appliances have two network interfaces configured, with a gateway in both? Are they the Ubuntu versions?
Userlevel 3
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

yes
Userlevel 6
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

OK, so we have the same setup. Ubuntu ifupdown doesn't like it if two interfaces have a gateway. dnetconfig (and well /etc/init.d/staticroutes) does something different that does work, by using Linux routing tables from the look of it. This makes ifupdown not complete on boot, so DNS (which it configures) isn't configured either.
Userlevel 3
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

Ok, great investigation! But I still don't get (sorry!) what you mean with "I got around to filing 01124098 on this"
Userlevel 7
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

I believe he's referring to the GTAC case he has opened 🙂
Userlevel 6
James A wrote:

I see this sometimes on my NAC servers with two NICs. It happens because /etc/network/interfaces has gateway lines for each interface, which causes a hang while the network is being configured, and so the DNS configuration is never set in /etc/resolv.conf. My guess is sometimes dnetconfig has a race condition with this which is why it only works sometimes. I've been meaning to file a bug on this but haven't got around to it.

Drew, that's exactly it. Would have replied earlier but I couldn't get the Extreme login to the community to work on my mobile.

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