Next, we need to set up some basic rules, please make sure to set up rules for the. This will install iptables-persistent and any dependencies. sudo apt-get update sudo apt install iptables-persistent -y. In short, I am banging my head in the wall and I’m starting to think to put my old Linksys router as a DialUp modem. There are lots of solutions you could use as your firewall, most are built on top of Linux iptables. Thankfully the LAN interface does not disconnect the ssh session, and I’m able to revert.

And at last, whenever I load an ipset, even with just a single IP the RPi losts connection - no ping in or out, no forward. That would be a problem if I try to do something remotely. Soon I realized that everytime I -reload the rules, I get an error “Error: Argument 1 does not allow None as a value”, the connection drops and no interfaces seems to be assigned to any zone until reboot.

Yes, now I know the MTU was the root of it and I have to clamp the MSS with:įirewall-cmd -permanent -direct -add-passthrough ipv4 -t mangle -I FORWARD -p tcp -syn -j TCPMSS -clamp-mss-to-pmtu. At first it took me and their tech support two days to figure out why some sites load and some not. Everyone was happy and the sun was shining.Īnd then, in their divine and endless wisdom, they decided to migrate their clients to PPPoE. I have not used it recently but this script makes that exceptionally easy.Until recently our ISP leased all their IP’s based on client MAC. However, to answer your question you can see if the port is open and what process is listening with the following command: sudo netstat -lptuĪdditionally you can test your basic configuration using telnet as described in this post.ĭepending on why you want an email server you may be better off just setting it up to forward all nonlocal mail through your Gmail account. The default configuration file should have automatically opened the port and be listening. I would suggest you implement SSL for your ingoing and outgoing mail which means that you will no longer be using port 25. Properly securing a mail server involves considerably more than a firewall though.Īs for port 25 It may be blocked by your ISP. However, if you intend on running a mail server you should install and configure a firewall first, as your server will be a prime target for spammers etc.

Also the default install will normally open and listen on the required ports. You likely don't have issues with iptables, unless you installed and configured it as it is not running on a default Raspbian install.

Raspberry pi firewall