Memory usage very high with recursion enabled

[Chris]

Dear All,

I had an issue on a number of DCs where the DNS service would often crash
(usually every 20 minutes) and the
memory usage is very high (over 400MB sometimes). Anyway even a
reinstallation didn't seem to fix it. I tried
disabling recursion (Advanced tab - not forwarders tab) and suddlenly the
memory usage dropped to a more
normal 4MB. I looked at the help and was a little confused what this option
basically did.

With this option being disabled I can still resolve to other DNS servers in
other domains using the forwarders,
I tried resolving from another domain to this domain and that worked OK. In
essence everything appears to
be working - no error messages no problems with naming resolution. The only
thing I notice is that nslookup
does not work with hosts outside my own DNS, it only works with local DNS
names even if I use the FQDN.

If I do a ping to a FQDN outside of my local DNS then that works. I cleared
out my cache and it still worked.
I also tried removing the addresses of the DNS from my NIC setting just to
see if it was really using DNS. When
I do that and use ping I get unknown host. I put the DNS addresses back in
and it resolves again.

So I seemed to be working OK. I was just interested to see if anyone had any
reasons for the high memory
usage and what I actually lose by disabling recursion under the advanced
tab, at the moment it seems to me I have not
lost very much at all.

Thanks
Chris

 

[Kevin D. Goodknecht Sr. [MVP]]

In

Dear All,

I had an issue on a number of DCs where the DNS service
would often crash (usually every 20 minutes) and the
memory usage is very high (over 400MB sometimes). Anyway
even a reinstallation didn't seem to fix it. I tried
disabling recursion (Advanced tab - not forwarders tab)
and suddlenly the memory usage dropped to a more
normal 4MB. I looked at the help and was a little
confused what this option basically did.

With this option being disabled I can still resolve to
other DNS servers in other domains using the forwarders,
I tried resolving from another domain to this domain and
that worked OK. In essence everything appears to
be working - no error messages no problems with naming
resolution. The only thing I notice is that nslookup
does not work with hosts outside my own DNS, it only
works with local DNS names even if I use the FQDN.

Your DNS server must have been answering from its cache, because disabling
recursion on the advanced tab disables it ability to resolve names it does
not have in its own database.

If I do a ping to a FQDN outside of my local DNS then
that works. I cleared out my cache and it still worked.
I also tried removing the addresses of the DNS from my
NIC setting just to see if it was really using DNS. When
I do that and use ping I get unknown host. I put the DNS
addresses back in and it resolves again.

So I seemed to be working OK. I was just interested to
see if anyone had any reasons for the high memory
usage and what I actually lose by disabling recursion
under the advanced tab, at the moment it seems to me I
have not
lost very much at all.

Check the Root Hints tab, to see if there are any other servers listed other
than the Root Servers.
Also, are the servers forwarding to each other? All servers should forward
outward if you are going to use a forwarder and _must_ _not_ forward to a
server that forwards back to it.

 

[Chris]

After writing this message, I was wondering if I had forwarders sending to
each other. I shall check and report back.

Thanks
Chris

 

[Herb Martin]

Dear All,

I had an issue on a number of DCs where the DNS service would often crash
(usually every 20 minutes) and the
memory usage is very high (over 400MB sometimes). Anyway even a
reinstallation didn't seem to fix it. I tried
disabling recursion (Advanced tab - not forwarders tab) and suddlenly the
memory usage dropped to a more
normal 4MB. I looked at the help and was a little confused what this option
basically did.

Most people don't expience any such problems so
likely it is something peculiar to your systems.

Let's start with which specific service pack and hot
fix level you are using?

 

[Chris]

Fixed it. Some of my servers were forwarding to each other.

Thanks to all
Chris