First we need to create dhclient.conf if it doesn't exist or edit it:
#add this line at the top add the IPs as commas they will be the highest priority nameservers and whatever your ISP gives you will be used after these one (good for DNS backup)
prepend domain-name-servers 127.0.0.1,10.10.25.8;
After you restart your network or run dhclient again you should see the contents of /etc/resolv.conf are as you expect.
This is mainly when you are running a local router and local DNS (and usually your own local DNS is quicker and more reliable than your ISP in my experience).