[CentOS] nameserver issue

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.
-- 
---- Fred Smith -- fredex at fcshome.stoneham.ma.us -----------------------------
               But God demonstrates his own love for us in this: 
                         While we were still sinners, 
                              Christ died for us.
------------------------------- Romans 5:8 (niv) ------------------------------