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Sep
3
awarded  Yearling
Apr
5
comment Can't communicate with SMTP server from particular machine
The "short cut" is to add the IP of your "bad server" in /etc/hosts on the mail server. But you might want to look into it a little deeper. If the mail server is unable to do DNS lookups, every host will get this delay. If it's just an issue with your "bad server" not having a DNS reverse mapping, I dont see why that would cause such a delay.
Apr
5
comment Can't communicate with SMTP server from particular machine
Although with TCP wrappers, it does drop/close the connection, so that may not be it... it could be doing a DNS reverse lookup as the previous commenter suggested. Try waiting for 60 seconds or more
Apr
5
comment Can't communicate with SMTP server from particular machine
On the mail server. Might as well check /etc/hosts.allow at the same time.
Apr
5
comment Can't communicate with SMTP server from particular machine
No, actually, that's the "normal" behaviour when something is blocked by TCP wrappers. It will allow the initial connection, but after that it drops. Try it with something like ssh and you'll see that exact behaviour.
Apr
5
answered Can't communicate with SMTP server from particular machine
Dec
14
comment Restrict SSH access to whitelist IP - what is stopping someone pretending to be from my IP?
See my comment below, but you're missing a fundamental notion of routing. Each router along the path will try to route the packet to the real destination, and not to the attacker. In the "bad old days" of the Internet, things like source routing were possible (the source could specify the return path) but that's practically impossible these days.
Dec
14
comment Restrict SSH access to whitelist IP - what is stopping someone pretending to be from my IP?
There's no luck involved, and no "catching the handshake". Each router along the path either knows a route to the remote IP (x.x.x.x) or it doesn't (and uses its default route). I don't know what you mean by getting "physically close enough to the server". If there is one router between them and the target and they control that router, great, they win. If there are two, they need to control both. If there are ten... you get the picture. If you don't see how this is possible, I recommend you read up a bit on IP fundamentals.
Dec
14
answered Restrict SSH access to whitelist IP - what is stopping someone pretending to be from my IP?
Nov
12
awarded  Nice Answer
Sep
3
awarded  Yearling
Dec
19
revised How to debug sporadic outbound connection timeouts?
edited body
Dec
19
revised How to debug sporadic outbound connection timeouts?
deleted 212 characters in body
Dec
19
revised How to debug sporadic outbound connection timeouts?
deleted 212 characters in body
Dec
19
answered How to debug sporadic outbound connection timeouts?
Dec
5
answered Why running named(bind) in chroot is so important for security? Or maybe it is not ?
Sep
3
awarded  Yearling
Jul
3
comment How can i find out why my web server is refusing traffic from my web proxy?
I don't think there's enough information here to say conclusively, but I'd start by looking closely at the proxy server. Is there anything in the logs? What is the current configuration? What is it allowing, and from/to which addresses? Also, you said "Recently, the web server has started refusing traffic"... what changed recently? Is there a firewall running on the proxy host itself?
Jun
21
awarded  Editor
Jun
21
revised After installing Mysql 5.6 the server can't start
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