listserv.traffic@xxxxxxxxx wrote:
Hello Don,
Monday, June 5, 2006, 8:45:37 PM, you wrote:
Ed Greshko wrote:
Don Russell wrote:
I added some information to my named configuration so sendmail could
resolve the reverse look up of the private LAN addresses.... or at least
get an error quickly instead of timing out
In order for this to work, I manually changed /etc/resolv.conf ,
deleting the exisiting nameserver statements, and adding nameserver
127.0.0.1
Works great.... UNTIL the network is restarted and the resolv.conf file
is rewritten.... then the nameserver statements are back to the
addresses from the ISP obtained via DHCP.
So, for an interesting experiment, I reconfigured the dhcp server in my
router (cisco) to not pass the ISP DNS addresses to my server, instead
use 127.0.0.1
Frankly, I wasn't expecting the server to be able to resolve any other
addresses.... but it does....
Why? Seems silly to be asking why something DOES work.... but I don't
understand how it can be resolving names like google.com, ibm.com etc
etc, when it was not told which dns servers to use, other than "ask
yourself"....
What am I missing? ;-)
In your named.conf do you have something like:
zone "." {
type hint;
file "named.root";
};
If so, you have told your DNS server what it needs to do.
Yes, I just looked at that... the file has a different name (named.ca),
but it seems to describe all the root servers....
I gather that means my FC5 box is now using the root servers directly to
resolve addresses instead of "lower", possibly caching, servers.
hmmm, that doesn't sound good... :-( But I'm pretty new to dns details....
IMO, it's a very GOOD thing. Esp. if your ISP is for crap. In that
case, if their DNS server aren't responding, you'll never even know
since your DNS server will resolve things properly.
The downside? Possibly slower resolves, since they are unlikely to be
as heavily cached as the ISP. Also, you have to make sure the DNS
server is configured right. If it isn't, then everything breaks.
But those downsides are pretty smallish IMO.
Different ball of wax if you're actually making that DNS server "auth"
for a DNS zone available on the net though. (You want
better/faster/more reliable connections for that.)
I'm using the "out of the box" named config files, I only added
authoritative stuff for 10.in-addr.arpa so sendmail and other services
that like to do reverse lookups would work better. (My LAN is in the
10/8 address space behind a NAT router)
Without that, sendmail has a long delay before replying to a client
connection.
Maybe this is a good thing.... maybe I can make my FC5 a DNS server for
my whole LAN (there's only a few PCs ... it's a home network)
hmmm, the dns server seems to cache results.... (2 digs to the same
name... first one 32mSec, 2nd one was 3mSec) so maybe this is great for
personal use.... that way the cache will fill up with addresses *I* go
to instead of the sites all the ISP customers go to.
I just tried to use the FC5 box as a DNS from one of the PCs, but it
timed out... I'm guessing the iptables rules aren't allowing that traffic.
