NAT – IT Blog

Port forwarding in iptables on NAT server

Once I needed to forward a port to a VPN server that had a gray IP address and was behind NAT.

Configuring BGP on Juniper MX – traffic balancing

I will give an example of setting up eBGP on Juniper MX204 with several uplinks and balancing traffic between them.

Juniper MX. How to send client traffic to a NAT server

Let’s say there is no default route on Juniper MX, or it is not suitable, or client traffic needs to be sent to different NAT servers, in this article I will describe how to do this.

Installing and configuring xt_NAT

I will give an example of installing and configuring xt_NAT on Ubuntu Server 14.04 with kernel version 4.4.0-142. xt_NAT may not work on newer kernel versions. According to the developer, it should work on Linux Kernel 3.18 and 4.1. To make it work on newer versions of the kernel, you can find patches.

Blocking SPAM behind a NAT server

In this article I will give an example of detecting and blocking the sending of spam messages behind a NAT server.

Changing gc_thresh on Linux

In this article I will give an example of changing gc_thresh on Linux, this parameter usually needs to be increased on highly loaded access servers.

NAT Modules for VPN, FTP, SIP

Let’s say SNAT or masquerading is configured on a Linux server, for example, as I described in article Ubuntu IP Masquerading (NAT). But if many NAT clients connect to external PPTP, FTP, SIP servers for NAT, then they will have connection problems.

Port forwarding on Mikrotik routers

To forward a port on the Mikrotik router, you need to open the “IP” – “Firewall” menu, select the “NAT” tab and add a new rule by clicking “Add new” or “+”.

Configure Hairpin NAT on RouterOS (Mikrotik)

In this article I will give an example of setting Hairpin NAT on RouterOS (Mikrotik).

I happen to have a server or a DVR in the local network, the ports to which are forwarded in the firewall, but you can connect only from other networks, and from the local network it is obtained only by the local IP address, but not external, on the WAN interface of the router.

Difference between MASQUERADE and SNAT

In this article I will briefly describe the difference between MASQUERADE and SNAT.

MASQUERADE. Less fast routing than SNAT with mass requests, since for each new connection an IP address on the external network interface (WAN) is determined. Great for home use routers and when changing the IP address on the WAN interface.
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