12 Aug
2014
12 Aug
'14
8:17 a.m.
Turns out you have to specify the interface address for sendmail to
respond to, 127.0.0.1 is default so that is why that always worked. I
never ran into that one before,
That explains this weirdness.. Two boxes on my local LAN with no
iptables software firewalls or hardware firewalls between them, and
selinux off on both:
[root@kb9mwr ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:21:85:9C:60:42
inet addr:192.168.1.100 Bcast:192.168.255.255 Mask:255.255.0.0
inet6 addr: fe80::221:85ff:fe9c:6042/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5421757 errors:0 dropped:0 overruns:0 frame:0
TX packets:4042659 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1012253009 (965.3 MiB) TX bytes:2506193160 (2.3 GiB)
Interrupt:58 Base address:0xe000
[root@kb9mwr ~]# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 kb9mwr.host.org ESMTP Sendmail 8.13.8/8.13.8; Mon, 11 Aug 2014
19:59:42 -0500
^]
telnet>
root@pbx:~ $ telnet 192.168.1.100 25
Trying 192.168.1.100...
telnet: connect to address 192.168.1.100: Connection refused
telnet: Unable to connect to remote host: Connection refused
I was well aware that most ISP's block that port but was really
stumped as to why to PC's on the same network could not talk to each
other on that port yet could on all other ports.
You learn something new every day.
12 Aug
12 Aug
8:24 a.m.
New subject: SMTP port 25
This is pretty standard out of the box setup if you need a local MX on a
server. You bind the server to the localhost (127.0.0.1). This way it
will not respond to other devices on the net.
In more detail, if you have an application that expects to use SMTP to
send mail, you point it to an MX bound to 127.0.0.1. It will receive
the mail and queue it up to be either delivered on the local box or to
send it to another server. This way you have an SMTP server that isn't
exploited as a relay.
Tim
On 8/11/14, 6:17 PM, kb9mwr(a)gmail.com wrote:
(Please trim inclusions from previous messages)
_______________________________________________
Turns out you have to specify the interface address for sendmail to
respond to, 127.0.0.1 is default so that is why that always worked. I
never ran into that one before,
That explains this weirdness.. Two boxes on my local LAN with no
iptables software firewalls or hardware firewalls between them, and
selinux off on both:
[root@kb9mwr ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:21:85:9C:60:42
inet addr:192.168.1.100 Bcast:192.168.255.255 Mask:255.255.0.0
inet6 addr: fe80::221:85ff:fe9c:6042/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5421757 errors:0 dropped:0 overruns:0 frame:0
TX packets:4042659 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1012253009 (965.3 MiB) TX bytes:2506193160 (2.3 GiB)
Interrupt:58 Base address:0xe000
[root@kb9mwr ~]# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 kb9mwr.host.org ESMTP Sendmail 8.13.8/8.13.8; Mon, 11 Aug 2014
19:59:42 -0500
^]
telnet>
root@pbx:~ $ telnet 192.168.1.100 25
Trying 192.168.1.100...
telnet: connect to address 192.168.1.100: Connection refused
telnet: Unable to connect to remote host: Connection refused
I was well aware that most ISP's block that port but was really
stumped as to why to PC's on the same network could not talk to each
other on that port yet could on all other ports.
You learn something new every day.
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Tim Pozar