-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Lee Parmeter Sent: Tuesday, May 17, 2005 11:48 AM To: centos@centos.org Subject: [CentOS] named server
I started the named server on CentOS and it seems to resolve DNS request OK, but it does not seem to retain the info for very long. From what I can tell using "dig", a domain's ip address is retained for less than 12 hours. So in the morning, it takes 4+ seconds to resolve again the first time. Is there an adjustment somewhere for this or is the caching named support not enabled by default?
Bind will use the Time To Live as configured by the owner of the domain name. There are other proxy DNS applications that allow you to override those values but I do not believe you can do so with bind.
Also, I thought it would be faster if I set named to use my ISP's named server as the first choice. Where do I set this up, in root.hints?
http://64.233.187.104/search?q=cache:OFlpPzQRRcUJ:www.rhce2b.com/clublin ux/RHCE-19.shtml+bind+forwarders&hl=en
19.3 Caching Only Name Servers
1. Not authoritative for any zone.
2. Uses DNS root servers or another name server known as a forwarder to resolve DNS queries.
3. To create a Forwarding Name Server, put the following line in the "options" section of the /etc/named.conf file:
forwarders { 192.168.1.20; }; # replace with your upstream nameserver
4. If you want BIND to only use it's forwarders to resolve hosts and not the root name servers, put the following line in the "options" section of the /etc/named.conf file:
forward only;
The "forwarders" option specifies which DNS or DNS servers queries should be forwarded to for resolution.
Anyone who knows more about "named" please feel free to comment!
Google knows a lot. =)
-- Marc
On 5/18/05, Marc Powell marc@ena.com wrote:
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Lee Parmeter Sent: Tuesday, May 17, 2005 11:48 AM To: centos@centos.org Subject: [CentOS] named server
I started the named server on CentOS and it seems to resolve DNS request OK, but it does not seem to retain the info for very long. From what I can tell using "dig", a domain's ip address is retained for less than 12 hours. So in the morning, it takes 4+ seconds to resolve again the first time. Is there an adjustment somewhere for this or is the caching named support not enabled by default?
Bind will use the Time To Live as configured by the owner of the domain name. There are other proxy DNS applications that allow you to override those values but I do not believe you can do so with bind.
Also, I thought it would be faster if I set named to use my ISP's named server as the first choice. Where do I set this up, in root.hints?
http://64.233.187.104/search?q=cache:OFlpPzQRRcUJ:www.rhce2b.com/clublin ux/RHCE-19.shtml+bind+forwarders&hl=en
19.3 Caching Only Name Servers
Not authoritative for any zone.
Uses DNS root servers or another name server known as a forwarder
to resolve DNS queries.
- To create a Forwarding Name Server, put the following line in the
"options" section of the /etc/named.conf file:
forwarders { 192.168.1.20; }; # replace with your upstream nameserver
- If you want BIND to only use it's forwarders to resolve hosts and
not the root name servers, put the following line in the "options" section of the /etc/named.conf file:
forward only;
The "forwarders" option specifies which DNS or DNS servers queriesshould be forwarded to for resolution.
What is the difference between use forward only+forwarders and directly set the nameserver inside resolv.conf ?
Anyone who knows more about "named" please feel free to comment!
Google knows a lot. =)
-- Marc _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On May 18, 2005, at 8:50 AM, Ceg Ryan wrote:
What is the difference between use forward only+forwarders and directly set the nameserver inside resolv.conf ?
resolv.conf is used by the system's name resolution service. BIND doesn't care about the contents of resolv.conf, as it has its own mechanism for resolving names (given that that is its primary function).
here are several scenarios that may illustrate the difference.
scenario 1 - you have set up a forwarding-only nameserver:
other machines can connect to your machine and ask it to resolve names for them. it will send those queries out to its forwarder, and when the responses come back, it will relay those responses to the machines that queried it. (incidentally, this machine's resolv.conf should be set up so that it queries itself for name resolution.)
scenario 2 - you have configured an external nameserver in resolv.conf, and you're not running BIND:
your machine will not respond to name service queries; however, it will still be able to resolve names itself.
scenario 3 - you have set up a forwarding-only nameserver (or any other instance of BIND), and you've also configured an external nameserver in resolv.conf:
this scenario is somewhat of a landmine. if other machines are depending on your machine for name resolution, but your machine uses the system's name resolution service to resolve names, then the following conversation can occur when BIND breaks:
User: Hey, I can't resolve www.google.com! Your nameserver isn't responding! You : Hmm, I just typed "host www.google.com", and it worked fine for me.
in a nutshell: resolv.conf and BIND have very little connection. if your nameserver is using a name resolution service other than itself, it can be easy to overlook DNS problems. if you're running a nameserver, its resolv.conf should point to itself (unless you have some special circumstance that requires otherwise).
does this make sense?
-steve
--- If this were played upon a stage now, I could condemn it as an improbable fiction. - Fabian, Twelfth Night, III,v
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Ceg Ryan -
Marc Powell -
Steve Huff