DNS servers change (auto) and become invalid

**nicholas22** · 03-18-2007, 10:02 PM

Hello Knoppix people,

I installed Knoppix today and I encounter the following problem:

I setup networking correctly but when I restart the DNS entries I inputted are gone.

So, every time I restart I have to put the DNS server addresses in the Networking panel.
(I need to be on a static IP)

The other entries are fine: IP, gateway, subnet.

Furthermore, after about 3 hours of uptime, the same problem occurs even if I do not restart...
It reverts to some IP address (its actually 172.16.176.x but I would like it to stay put on 192.168.1.1)

Any help would be much appreciated.

Initially I am thinking of amending the /etc/resolv.conf file permissions so that Knoppix does not change it but would like your opinion first.

Thanks

**Harry Kuhman** · 03-18-2007, 11:13 PM

Originally Posted by nicholas22

It reverts to some IP address (its actually 172.16.176.x but I would like it to stay put on 192.168.1.1)

The common 192.168.xxx.xxx range and the range 172.16.0.0 - 172.31.255.255 are both ranges reserved for private IP addresses. But why your system would jump between them is a mystery that we don't yet have the information to know. Please see answer #3.

Originally Posted by nicholas22

I installed Knoppix today ....

This could well be a big part of your problem.

**nicholas22** · 03-18-2007, 11:52 PM

My NIC is an Yukon Marvell 88E8001 GbLAN

Router: Linksys BEFSR81 on 192.168.1.1

I'm on Cable (not a static public IP, but has not changed for the last 3 years I live here)

I set up the following:
IP: 192.168.1.254
Subnet: 255.255.255.0
Gateway: 192.168.1.1

I originally setup as DNS servers my ISP name servers but since I keep losing them I just input 192.168.1.1 now and my router sorts DNS out.

A listing of when I am properly setup:

eth1 Link encap:Ethernet HWaddr 00:11:2F

2:86:1E
inet addr:192.168.1.254 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::211:2fff:fed2:861e/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4281 errors:0 dropped:0 overruns:0 frame:0
TX packets:4705 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2959566 (2.8 MiB) TX bytes:904500 (883.3 KiB)
Interrupt:18

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:68 errors:0 dropped:0 overruns:0 frame:0
TX packets:68 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:6594 (6.4 KiB) TX bytes:6594 (6.4 KiB)

vmnet1 Link encap:Ethernet HWaddr 00:50:56:C0:00:01
inet addr:172.16.176.128 Bcast:172.16.176.255 Mask:255.255.255.0
inet6 addr: fe80::250:56ff:fec0:1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:113 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

vmnet8 Link encap:Ethernet HWaddr 00:50:56:C0:00:08
inet addr:192.168.129.128 Bcast:192.168.129.255 Mask:255.255.255.0
inet6 addr: fe80::250:56ff:fec0:8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:11 errors:0 dropped:0 overruns:0 frame:0
TX packets:114 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)

The vmnet interfaces were added by VMWare player

I will restart now and post an ifconfig output of when I'm on the wrong DNS again...

**nicholas22** · 03-19-2007, 12:00 AM

Well the output from ifconfig is the same as it does not mention dns.

The DNS was changed again to 172.16.176.1.

I pinged it and ns-looked it up, both before and after; no replies no dns info.

So again the 1 million dollar question is why does it keep changing it to that?

Your help is much appreciated

Thanks again

**nicholas22** · 03-19-2007, 12:11 AM

When I installed to HDD I chose Debian-style, so I don't think this is related to the Knoppix-like version reverting back

(saw this in another thread)

**Harry Kuhman** · 03-19-2007, 01:24 AM

The most common way to setup a network when using a Linksys router is not to make any settings at all, just do DHCP to the router and let it make the assignments. One down side to this is that it may be hard to lock particular local IP addresses to particular computers, and this makes port forwarding for servers a pain. But if that's not an issue I would certainly try to go with DHCP.

I'm mystified as to where the 172.16 addresses are coming from. This is a private unroutable range, so it can't have anything to do with your ISP's real DNS servers. I'm not even clear if it's coming from your router or from something else. I don't really expect that it is coming from the router, but I would do the following: Enter the router setup and see what DNS servers it says it is using; confirm they are real routable addresses. Consider using them instead of the router's 192.168.x.1 address. Check if there is a newer version of firmware for that router. If not, at least reset the router and see if that helps. Or if you have an alternate router that you could try, use it temporarly and determine if the router is a factor at all.

I'm not really concerned about the type of Knoppix install you did. I've seen enough reports of strange problems after any type of Knoppix install (except perhaps the "poor man's install"), and particularly networking problems, that I have come to believe it's always a questionable idea. I have never had a problem like this into any of my routers with real Debian installs.

**nicholas22** · 03-19-2007, 01:57 AM

Yes unfortunately I need to forward some ports (Azureus and others) to this machine.

But I tried that anyway and I can't activate the interface when I use DHCP...
The error message: Check that the network settings are correct and the machine connected to it.
But DHCP worked on the Knoppix LiveDVD 5.1.1 which I used! (was used to install to disk)

There are about 5 windows machines on DHCP on this network so I don't think there is a problem with the DHCP settings of the router.

The same thing happens when I use the DNS servers provided by my ISP. They disappear on a reboot or arbitrarily after some hours.

I've never seen such behaviour on this network and have been using a static IP on WinXP for more than 2 years so I'm pretty certain its something in my new setup or configuration. I have kept my WinXP partition and this doesn't seem to happen. DHCP works as well there.

Any ideas?

Do you think that changing the /etc/resolv.conf file permission to non-writeable is ok to try as a workaround?

Many thanks