RHEL / CentOS nmcli madness II

While writing, last weeks post became pretty awesome and should be a great, solid basis for your understanding of nmcli and network configuration in general. This week I’ll be getting more into the RHCE part of nmcli: teaming network interfaces for high availability, backup and failover and aggregation. Let’s get started.

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RHEL / CentOS nmcli madness I

RHCSA is in the bag. I took the RHEL 8 exam and passed with a whopping 283 of 300 points. Next up is RHCE 7 (version 8 is completely Ansible related which will come at a later time), which for me is a whole different ballgame. So what about this nmcli madness? Continuing my RHEL…

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BIND primary and secondary DNS server

Last weeks BIND post cost me more time than I could’ve imagined. You can have a forwarding or caching server running in a matter of minutes, but fiddling with listening addresses and ACLs took me a bit more time. In retrospect, it was not hard, but I stumbled upon a couple of problems like the…

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BIND forwarding and caching DNS server

For my recent exam I had to study how to setup a BIND caching DNS server. Since this was too easy, I decided to make it a full featured primary and secondary DNS server, but that’s for the next post. I mentioned the BIND setup with a colleague of mine and he, somewhat jokingly, asked…

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SMTP – Checks

Ouch, I thought with the last post to conclude the SMTP series, but I forgot one element: how to check these services, if they are operating like they should. The anti-spam triangle, how I myself decided to call it, consists of DMARC, SPF and DKIM,as I’ve covered in the previous post. Now a few simple…

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SMTP – DKIM DirectAdmin with Exim 4

So we had these awesome DirectAdmin posts, although I do not like DirectAdmin one little bit, which got me started with the SMTP posts, this being the last one about DKIM. After getting this cool mechanism configured on Postfix with and without Rspamd, this time we’ll be configuring it on a DirectAdmin enabled server with…

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SMTP – DKIM with Postfix

The first email server I’ve configured with DKIM was a Postfix server with Rspamd, hence the previous post about this. But soon I also needed this cool mechanism configured on a server with postfix only and no Rspamd involved.It needs some more work I guess, but following this guide will get you there. I’ll make…

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SMTP – DKIM Postfix with Rspamd

After a few easy ones (DMARC and SPF), we now have the last one in our anti-spam triangle, DKIM, which is more complicated to setup. This mechanism is probably also the most reliable and hack proof solution, since you need to configure your email server, your DNS records and combine the two to make it…

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SMTP – SPF

After DMARC, the next in the spam fighting triangle (DKIM being the third) is SPF. A SPF record (Sender Policy Framework) was originally to help the fight against SPAM but quickly became obsolete. Nevertheless we still need it for most providers like Gmail and Outlook.com. So, although its kind of useless, we still need to…

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SMTP – DMARC

Following up on the first SMTP post, this next one is probably easiest: the DMARC record. Getting it active on your domain can take a few seconds and maybe a more complicated setup a few minutes. As simple as this mechanism is to set up, it’s always has been pretty solid against the abuse of…

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SMTP – Backscatter check

I will dedicate the next couple of posts on a few on these mechanisms and checks. The first is to check for Backscatter. Backscatter is when a NDR (Non Delivery Report) or bounce message contain the full body of a mail / spam message. After the recent DirectAdmin posts there was a lot to do…

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Nextcloud 12 migration guide

Following one of the better decisions a couple of days ago, it was time today to re-install my webserver that runs Nextcloud. I made some errors setting it up, now almost a year ago. A couple of things could be fixed, a couple of things I’d rather not and just build it from the ground…

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New Zimbra 8.7.11 server migration guide

In the past I haven’t been so kind about the Zimbra Open Source Suite. Installing it in my own, configuring it, getting all my data to it and using it daily wasn’t a breeze. I found it especially difficult to keep it stable while ensuring security. I’ve also been somewhat active at the forums and…

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IPv6 on CentOS 6 and CentOS 7.4 VPS

For almost 20 years I’m working in IT and I hear “we’re running our of IPv4 addresses” and “IP version 6 is coming”. Although this is the truth, there are still not a lot of situations I come across that I need an IPv6 address. And then there was this situation where I very recently…

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Addendum OSI model / PDUs

I would  like to make a small addendum to my previous post about the OSI model and PDUs. What was named quickly in the Network+ videos was what protocols actually function on which layers, which I found interesting. So let me enrich you with a few examples! To clarify a little bit, after mentioning the…

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