NAT

Mikrotik routers are rightly valued by system administrators for their incredible flexibility.
A unique feature of this hardware is that a budget home hAP lite and a powerful enterprise router costing thousands of dollars run the same operating system — RouterOS.

That means once you learn to configure one device, you can manage any equipment from the brand.
In this article we’ll go over the fundamental steps to set up a Mikrotik from scratch to a fully working state.

This article is compiled as a “cheat sheet” for SOHO/SMB networks: common issues, their symptoms, causes, quick fixes, and diagnostic checklists. Suitable for both engineers and admins who maintain the MikroTik ↔ Keenetic bundle.

📑 Navigation

• EoIP “freezes” when transferring large files
• Site-to-Site VPN is up, but traffic doesn’t pass
• NAT breaks VPN/EoIP
• MTU/MSS: how to choose correctly
• Policy Routing (RouterOS 7)
• SMB from another subnet doesn’t work
• Quick diagnostics checklist
• Command cheat sheet
• Typical MTUs for tunnels
• NAT/Firewall exceptions matrix
• Common pitfalls
• Visualizations
• Resources and documentation

1) EoIP “freezes” when transferring large files

Symptoms: SMB/FTP hangs, speed fluctuates, RDP drops. Causes: incorrect MTU/MSS, fast-path with IPsec, NAT/Firewall errors.

In the world of networking, there’s often a need to bridge two remote LANs so they behave like a single local network—even when separated by different routers. For MikroTik users, the concept of EoIP (Ethernet over IP) is familiar: it’s a proprietary tunneling protocol that allows creation of a virtual Ethernet interface (Layer 2) over an IP network.

Good news for Keenetic users: since firmware NDMS v2.10, Keenetic routers also support EoIP! This opens up exciting possibilities for advanced network designs.