Network troubleshooting: Difference between revisions

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m (Mip moved page Network to Network troubleshooting: There are already a network page. This one is only about troubleshooting.)

Revision as of 05:59, 8 June 2016

Troubleshooting network issues

  • Ping DNS server
8.8.8.8       Google DNS server
195.238.2.21  Belgacom DNS server
  • Ping gateway (see netroute)

Can't connect to SMTP server

I can connect to smtp server locally:

nc localhost 25
220 www.immie.org ESMTP Exim 4.84_2 Mon, 06 Jun 2016 20:28:47 +0200

But when using the IP address, it does not work:

nc immie.org 25
immie.org [91.134.134.85] 25 (smtp) : Connection refused

The firewall is configured to accept connections though:

iptables -L|grep smtp
ACCEPT     tcp  --  anywhere             anywhere             tcp multiport dports smtp,submission

In fact, we have a DNS issue:

nc -v -v immie.org 25
DNS fwd/rev mismatch: immie.org != vps282013.ovh.net
immie.org [91.134.134.85] 25 (smtp) : Connection refused
sent 0, rcvd 0