Having successfully killed my (Centos 7) mail server I have had to build a new one.
Thankfully I had a server build that I was about to start configuring as my new web server.
I appear to have set everything up okay, Exim, SpamAssassin, ClamAv, Dovecot, Postgresql, httpd etc.
Everything appears fine apart from when I try to connect to my web server. Whatever tried to connect suffers from a delay, and either times out or works eventually.
I started off with problems connecting Exim to Postgresql on the web server. I then found that I couldn't connect using psql, or using Perl DBD-Pg. I then found I couldn't SSH or SCP, dispite them both being on the same subnet.
The more I use the new system, better it appears to be, but the delay is still there.
name resolution isn't the problem as I can nslookup both ways without problems, and specifying IP addresses makes no difference. For testing I have disabled the firewall and selinux and that made no difference.
If I try to connect the other way there is no delay, but I cannot access the Postgresql server on my new mail server from the web server.
Anyone got any ideas?
On 05/24/2018 09:10 PM, Gary Stainburn wrote:
name resolution isn't the problem as I can nslookup both ways without problems
Can you provide more detail here regarding what tests you performed? Long delays are usually a timeout on a reverse DNS lookup (that is, a PTR lookup) on the connecting IP address.
Connect to the server, and get the address that the server sees as its peer either from the log or using "ss -o state established -t". Use "time host $ip" to test the reverse lookup. Send the output to the list.
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Gary Stainburn -
Gordon Messmer