Routeros L4 Vs L5 ✦ Trusted Source

A small hosting provider peers with two upstream ISPs via BGP, accepting a full routing table (900,000+ IPv4 routes). They use a CCR2004. An L5 license is the minimum here, not because of bandwidth, but because L4’s routing table memory allocation is limited to 512,000 routes. L5 expands this to 2,000,000 routes. With L4, the router would crash or freeze during BGP convergence. The Upgrade Path: The $95 Question Upgrading a device from L4 to L5 currently costs $95 (MSRP). For a $60 home router, this is uneconomical; you simply buy a higher-tier device. But for a $500 CCR, the upgrade is a strategic investment. However, one must ask: Are you buying a license or a feature? Many users mistakenly believe that upgrading from L4 to L5 on an old RB951Gi will make it faster. It will not. The hardware limitations (slow CPU, 128 MB RAM) will cap performance long before the license becomes the bottleneck. Upgrading the license only unlocks logical capacity; it does not improve processing power. Conclusion: The License as a Design Philosophy RouterOS L4 and L5 are not simply two versions of the same software; they represent two distinct philosophies of networking. L4 is the license of the edge—the gateway, the home router, the small office firewall. It says, “You are a leaf node, connecting a few networks to the rest of the world.” L5 is the license of the distribution and core—the aggregator, the tower router, the BGP peer. It says, “You are a hub, responsible for synthesizing many connections into a coherent fabric.”

A rural WISP has 150 customers on a single tower. They use one 5 GHz backhaul to a core router, three 5 GHz sectors (90 customers), and one 2.4 GHz sector (60 customers). This requires 5 wireless interfaces, exceeding L4’s limit of 3. Furthermore, they use OSPF to route customer subnets back to the core. L5 is mandatory. Attempting this with L4 would result in the software refusing to enable the fourth radio interface. routeros l4 vs l5

So why would anyone buy L5 for a physical machine? Because of session table limits. An L4 router, regardless of CPU, has a compiled-in maximum of 200,000 concurrent NAT/firewall connections. An L5 router allows up to 1,000,000 connections. In a modern network with P2P traffic, WebRTC, and DDoS attacks, 200,000 connections are surprisingly easy to exhaust. Once the connection tracking table is full, the router begins dropping new valid traffic. L5 provides the headroom for high-density environments. To synthesize the analysis, consider three distinct scenarios: A small hosting provider peers with two upstream

Choosing between them requires brutal honesty about your network’s scale and growth trajectory. If you have three wireless interfaces, fewer than 200 remote users, and a simple routing topology, L4 will serve you faithfully for a decade. But the moment you add a fourth radio, deploy VPLS, or peer with a second upstream BGP provider, you will slam into the invisible walls of L4. Those walls are not bugs; they are deliberate market segmentation. Understanding where those walls lie—and whether your network will ever approach them—is the mark of a mature network engineer. In the MikroTik world, the license is not a suggestion. It is the constitution of your router’s reality. Choose wisely, not for the bandwidth you have today, but for the routing table you will need tomorrow. L5 expands this to 2,000,000 routes

L5, by contrast, is the entry point for “service provider” capabilities. It is the license required for a router to act as an MPLS Label Edge Router (LER) or Label Switch Router (LSR) in a production environment. While L4 permits MPLS, it lacks the necessary control plane memory allocation for complex L3VPNs. An L5 license enables the router to participate in VPLS (Virtual Private LAN Service) and MPLS TE (Traffic Engineering). For a WISP or a metro Ethernet provider, L4 is suitable for a customer premise equipment (CPE) device. L5 is the minimum requirement for a distribution or core node. MikroTik’s wireless stack (the legacy one, not the new WiFiWave) is heavily license-dependent. An L4 router can run three wireless interfaces. This is ideal for a home router: one 2.4 GHz interface for legacy clients, one 5 GHz interface for modern clients, and one interface dedicated to a wireless bridge. However, a WISP tower cannot survive on three interfaces. A tower requires one 5 GHz backhaul, two 2.4 GHz sector antennas, and two 5 GHz sector antennas—that’s five interfaces, requiring L5.

A user has gigabit fiber, 50 IoT devices, 5 family members, and runs a VPN server for remote access. They will never exceed 200 PPPoE clients or 3 wireless interfaces. An L4 license (often bundled with the hAP ac³ or RB450Gx4) is perfect. Upgrading to L5 would provide zero tangible benefit, as the session table will never exceed 20,000 connections.