Hi all!
This question is, at best, somewhat peripheral to Centos, but I'm hoping to be forgiven, and that someone here can give me a clue.
I've just brought up a nameserver on my household LAN, bind9 on a Raspberry Pi.
The connection with Centos is this: my main desktop is C7, and its hardwired network is also manual, not dhcp. I've edited the ipv4 config (in NM) and changed the DNS settings from 192.168.2.1 (the router) to 192.168.2.2 (the RPi). I've also manually tweaked /etc/resolv.conf to contain 192.168.2.2 instead of 192.168.2.1.
works fine. until I fire up a vpn. having done that, looking in /etc/resolv.conf (while the vpn is connected) it has reverted to 192.168.2.1.
after shutting down the vpn, 192.168.2.1 remains in resolv.conf
what am I overlooking here?
now the not-so-Centos-related question: I've changed the dhcp settings in my router so it should deliver 192.168.2.2 to the dhcp clients instead of 192.168.2.1. And it does, sorta. all the systems that use DHCP, now are configured with two DNS server addresses, 192.168.2.2, and 192.168.2.1. And I have no clue why 192.168.2.1 is still showing. Both windows and Linux systems are showing this behavior.
Clues appreciated!
and thanks in advance.
--On Thursday, April 20, 2017 12:34 AM -0400 Fred Smith fredex@fcshome.stoneham.ma.us wrote:
works fine. until I fire up a vpn. having done that, looking in /etc/resolv.conf (while the vpn is connected) it has reverted to 192.168.2.1.
after shutting down the vpn, 192.168.2.1 remains in resolv.conf
Which VPN? It's not uncommon for VPN software to change the resolver setting to point to your VPN peer's DNS, so that all traffic goes through the VPN, including your DNS traffic.
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On Thu, Apr 20, 2017 at 12:32:41AM -0700, Kenneth Porter wrote:
--On Thursday, April 20, 2017 12:34 AM -0400 Fred Smith fredex@fcshome.stoneham.ma.us wrote:
works fine. until I fire up a vpn. having done that, looking in /etc/resolv.conf (while the vpn is connected) it has reverted to 192.168.2.1.
after shutting down the vpn, 192.168.2.1 remains in resolv.conf
Which VPN? It's not uncommon for VPN software to change the resolver setting to point to your VPN peer's DNS, so that all traffic goes through the VPN, including your DNS traffic.
I use OpenConnect VPN for this pareticular task.
and yes I know the vpn changes it, then should put it back when one disconnects.
problem is, where is it getting the old address from? It isn't in the resolv.conf before the vpn is started, and it is not in the NM setups, anywhere, and it isn't in any of the files in /etc/sysconfig/network*, so where is it coming from? And that particular system is NOT using DHCP. Beats me!
Fred
--On Thursday, April 20, 2017 9:10 AM -0400 Fred Smith fredex@fcshome.stoneham.ma.us wrote:
problem is, where is it getting the old address from? It isn't in the resolv.conf before the vpn is started, and it is not in the NM setups, anywhere, and it isn't in any of the files in /etc/sysconfig/network*, so where is it coming from? And that particular system is NOT using DHCP. Beats me!
Good question. Could systemd be involved? I found this bug:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1624317
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On Fri, Apr 21, 2017 at 08:34:29AM -0700, Kenneth Porter wrote:
--On Thursday, April 20, 2017 9:10 AM -0400 Fred Smith fredex@fcshome.stoneham.ma.us wrote:
problem is, where is it getting the old address from? It isn't in the resolv.conf before the vpn is started, and it is not in the NM setups, anywhere, and it isn't in any of the files in /etc/sysconfig/network*, so where is it coming from? And that particular system is NOT using DHCP. Beats me!
Good question. Could systemd be involved? I found this bug:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1624317
I'll take a look at that, thanks.
I also have more info...
My router is stupid. apparently it sends to the dhcp clients the nameserver address you enter into the dhcp configs, but it appends its own LAN address to it so the clients get both:
https://www.snbforums.com/threads/dns-problems-with-dhcp.23132/#post-319233 that is a discussion of a similar router from the same mfg as mine, and it behaves the same way.
You can see this directly if you have a windows system, run "ipconfig /renew" then "ipconfig /all" and you'll see both addresses listed as DNS.
Now, does that have anything to do with my Centos box which is manually configured? I can't see how, but it makes me wonder.
-
Fred Smith -
Kenneth Porter