DNS Issue?

unclouded · October 16, 2008, 7:31am

Hello all -

I recently switched my setup to use internal 10.0.0.x IPs for the
backend webserver connections. For 18-19 hours, it was fine, but now
I’m seeing issues. Each requests takes a LONG time to return. If I
switch back to the publicly accessible IPs, things work fine.

Any thoughts? Perhaps it’s trying to some sort of dns lookup and
failing?

Thanks!

unclouded · October 16, 2008, 8:23am

Hmmm, it appears we have general problems with using our 10.0.0.x
addresses. For example, doing something like:
ssh 10.0.0.2
takes a LONG time to return.

If I do something like
123.123.123 (my public IP),
things return promptly.

Perhaps this is a general networking question less than
nginx-specific, but thought I’d check if anyone has any good
suggestions! Thanks!

unclouded · October 16, 2008, 8:29am

On Wed, Oct 15, 2008 at 11:16 PM, Neil S. [email protected] wrote:

nginx-specific, but thought I’d check if anyone has any good
suggestions! Thanks!

Let me guess your sshd is doing reverse DNS lookups and you have no
internal DNS serving your 10.x.x.x network.

Cheers
Kon

unclouded · October 16, 2008, 8:43am

Hi Niel,

Have you traced the backend connection with tshark or ngrep to see what
traffic is flowing between nginx and your backend machines ?

Cheers

Dave

On Wed, 15 Oct 2008 22:24:52 -0700, Neil S. [email protected] wrote:

Hello all -

I recently switched my setup to use internal 10.0.0.x IPs for the
backend webserver connections. For 18-19 hours, it was fine, but now
I’m seeing issues. Each requests takes a LONG time to return. If I
switch back to the publicly accessible IPs, things work fine.

Any thoughts? Perhaps it’s trying to some sort of dns lookup and
failing?

unclouded · October 16, 2008, 11:11am

Try adding an entry for it in /etc/hosts

unclouded · October 16, 2008, 11:22am

I just added the following in the /etc/hosts file for each of my
servers:

10.0.0.2 mydomain.com
10.0.0.3 mydomain.com
10.0.0.4 mydomain.com
10.0.0.5 mydomain.com
10.0.0.6 mydomain.com
10.0.0.7 mydomain.com
10.0.0.8 mydomain.com
(repeated for each IP I have assigned)

A bit tedious, but seems to have solved the issue. Any downsides to
this?

Thanks!

unclouded · October 16, 2008, 12:45pm

Basically, Kon was on point. Set up an internal DNS.

Since you have atleast 8 servers, and I guess probably more, you really need to think about using a local DNS, or you will have to modify the hosts file on each one of those when&if you make changes.

Lp

Neil S. wrote:

I just added the following in the /etc/hosts file for each of my servers:

10.0.0.2 mydomain.com
10.0.0.3 mydomain.com
10.0.0.4 mydomain.com
10.0.0.5 mydomain.com
10.0.0.6 mydomain.com
10.0.0.7 mydomain.com
10.0.0.8 mydomain.com
(repeated for each IP I have assigned)

A bit tedious, but seems to have solved the issue. Any downsides to
this?

Thanks!

On Thu, Oct 16, 2008 at 2:04 AM, CryptWizard <[email protected]>
wrote:

Try adding an entry for it in /etc/hosts
On Thu, Oct 16, 2008 at 7:13 PM, Neil S. <[email protected]> wrote:

I think this IS the issue, Kon. For example, I do:
traceroute -n 10.0.0.2
Returns immediately

I do
traceroute 10.0.0.2
Takes quite some time.

Thoughts on how to resolve this? Perhaps my settings in ifcfg-eth1
aren’t complete?

On Wed, Oct 15, 2008 at 11:23 PM, Kon W. <[email protected]> wrote:

On Wed, Oct 15, 2008 at 11:16 PM, Neil S. <[email protected]> wrote:

Hmmm, it appears we have general problems with

using our 10.0.0.x

addresses.  For example, doing something like:

ssh 10.0.0.2

takes a LONG time to return.
If I do something like

123.123.123 (my public IP),

things return promptly.
Perhaps this is a general networking question less than

nginx-specific, but thought I’d check if anyone has any good

suggestions!  Thanks!

Let me guess your sshd is doing reverse DNS lookups

and you have no

internal DNS serving your 10.x.x.x network.
Cheers

Kon
    </pre>
  </blockquote>
</blockquote>
<pre wrap="">
</pre>

unclouded · October 16, 2008, 7:48pm

I’m still not sure “what” is doing the lookup - nginx? Apache on the
backend? (I have HostnameLookup off there.)

unclouded · October 16, 2008, 10:32am

I think this IS the issue, Kon. For example, I do:
traceroute -n 10.0.0.2
Returns immediately

I do
traceroute 10.0.0.2
Takes quite some time.

Thoughts on how to resolve this? Perhaps my settings in ifcfg-eth1
aren’t complete?