Red HatThis forum is for the discussion of Red Hat Linux.
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Introduction to Linux - A Hands on Guide
This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter.
For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.
Click Here to receive this Complete Guide absolutely free.
Good to be back doing a linux task again. It's been a long time!
So here's my question:
I have two machines:
A.domain.com: (Old mail server): Red Hat 9 (Linux 2.4.20-30.9)
B.domain.com: (New mail server): RHEL Client 5 (2.6.18-164.2.1.el5)
(Both machines are in the same subnet and on the same switch).
I wanted to test the new mail server by sending an E-mail message
to it from the old one, but the maillog says
Jan 15 14:42:39 A sendmail: o0FJgXg9002731: to=<user@B.domain.com>,
ctladdr=<user@C.com> (1036/100), delay=00:00:00, xdelay=00:00:00, mailer=esmtp,
pri=30532, relay=B.domain.com. [x.x.x.x], dsn=4.0.0, stat=Deferred: B.domain.com.:
No route to host
I can ping from A.domain.com to B.domain.com and from B.domain.com to A.domain.com
I can traceroute -p 25 from A.domain.com to B.domain.com and from B.domain.com to A.domain.com
I can *telnet* on port 25 from B.domain.com to A.domain.com
BUT when I telnet on port 25 from A.domain.com to B.domain.com
I get "telnet: connect to address x.x.x.x: No route to host"
The resolved IP x.x.x.x is correct by the way. So I see no reason why
it should fail to telnet on port 25 to A.domain.com.
First test is with pinging, second with telnet to port 25.
Next are with loking at the log of B.domain.com mailserver, to see why it is denying connections. Security measures like it denies if DNS record for domain and connecting IP are not the same? Or B server can not get reverse DNS record for IP of the A server?
Regarding your suggestion, "First test is with pinging, second with telnet to port 25",
please see my original post.
/var/log/maillog log in B.domain.com shows no entries when A.domain.com tries to
connect to send it the E-mail.
If I do:
telnet x.x.x.x 25
telnet: connect to address x.x.x.x: Connection refused
telnet: Unable to connect to remote host: Connection refused
But if I do:
telnet localhost 25
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 B.domain.com ESMTP Sendmail 8.13.8/8.13.8; Mon, 18 Jan 2010 14:21:56 -0500
The Firewall is disabled right now, so what could prevent
B.domain.com from telnetting to itself on port 25 ?
I found the problem. I needed to let sendmail listen to traffic
from other IPs other than localhost on port 25. So in sendmail.cf
O DaemonPortOptions=Port=smtp,Addr=127.0.0.1, Name=MTA
O DaemonPortOptions=Port=smtp,Addr=x.x.x.x, Name=MTA