Don Russell wrote:
On 4/4/2006 4:29 AM, Paul Howarth wrote:
Don Russell wrote:
I'm using FC5 and have the "nightly yum update" turned on.
My FC5 box runs a mail server.
Yesterday, there were no problems.
Today, I can't send mail from PCs on the network... the Thunderbird
client
says "Connected to 10...." and eventuaally times out.
From external machines I can telnet to port 25 and it takes anywhere
from
40-80 seconds to get a reply from the server.
If I'm on the same machine as the server, the connection is immediate.
That tells me it is not smtp that's slow, but something relating to
external connections.
I have not changed any configurations... but with the nightly updates,
what could account for introducing such a delay?
I'm thinking somethin like it's trying to a reverse dns look up to
check
the address connecting, and that's taking a long time?
Any ideas/suggestions?
Check that your nsswitch.conf has an appropriate hosts entry.
hmmm, I don't know what's "appropriate". :-(
The nsswitch.conf file looks pretty generic... the "hosts" line says:
hosts: files dns
That looks OK.
Guessing, I changed that to
hosts: files dns [NOTFOUND=return]
then "service network restart"
but that had no effect...
hmmm, do I need to have my PCs listed in /etc/hosts ?
No. Sendmail needs to look up MX records, which it can't get from a
hosts file anyway.
If so, that means something changed because this was all working fine the
other day... could a "nightly yum" have wiped out my /etc/hosts file?
Which new packages were installed on the night in question? (check
/var/log/yum.log)
Check that /etc/resolv.conf points to nameservers that are working.
Try using "dig" to check them out, e.g.
$ dig @first.name.server -x 212.56.100.58
See how long the lookups take.
I tried several times with the two dns addresses in /etc/resolv.conf and
the longest query time was 180mSec, the shortest was 25mSec.
However, I also tried dig @dns-server - x 10.10.10.13
(the 10. address is my PC that tries to connect to my mail server at
10.10.10.250)
That timed out after 15 seconds.... expected, but far short of the delay I
see when I "telnet 10.10.10.250 25" from 10.10.10.13
Doesn't really sound like a DNS issue then.
Paul.
