By default the CRS come in Router mode, if the CRS is with SwitchOS then you can see in the System menu -> RouterBoard in the settings button, if you can boot the device in RouterOS mode.

Changing a MikroTik CRS (Cloud Router Switch) device to function as a router instead of a switch can be useful in situations where you need advanced routing capabilities, such as inter-VLAN routing, dynamic routing, or implementing security policies. more complex firewalls.

CRS devices are designed to function primarily as Layer 2 switches, but also support Layer 3 routing functionality thanks to the powerful RouterOS they run. Here I guide you on how you can make this change:

1. Access your MikroTik CRS

First, you need to access your device. You can do this through WinBox, WebFig, or SSH. WinBox is a graphical management tool for MikroTik devices and is the easiest to use for those who prefer a graphical interface.

2. Change the Operation Mode

To change the CRS to function as a router, you must adjust its settings to disable the switch-chip (for models that have it), allowing the device's CPU to handle routing. This is usually done by disabling the master-port or switch functions on the interfaces and configuring routing through the CPU.

In WinBox:

• Go to Bridge → Ports.
• Removes existing ports from any bridge or switch configuration that are assigned. This is done by selecting the ports and clicking “Remove”.
• Then go to Interfaces and make sure each interface is configured individually, not assigned as part of a switch group.

3. Configure Routing

Now that your device is ready to act more like a router, you can start configuring routing according to your needs. This includes configuring IP addresses, static or dynamic routes, firewall policies, NAT, and any other necessary routing features.

• Configure IP Addresses: go to IP → Addresses and add IP addresses to the interfaces you need.
• Configure Static Routes: If necessary, go to IP → Routes and add the static routes.
• Enable Inter-VLAN Routing: If you are using VLANs, configure the VLAN interfaces to Interfaces → VLAN and assigns appropriate IP addresses.

4. Additional Settings

• Firewall and NAT: Don't forget to configure firewall rules in IP → Firewall to protect your network. If you're sharing an Internet connection, you'll probably also need to configure NAT in the NAT of the firewall.
• DHCP Server: If you need your device to automatically assign IP addresses to your clients, set up a DHCP server on IP → DHCP Server.

5. Test and Verify

After making these changes, it is crucial to verify that everything is working as intended. Perform ping tests, verify routes, and ensure traffic is flowing correctly through the device.

Changing a CRS to function as a router can have performance implications, especially on models that are optimized for high-speed switching operations using a dedicated switch-chip.

When routing through the CPU, performance may be affected depending on the volume of traffic and the specific routing tasks being executed. It is important to keep this in mind when planning to use a CRS as a router.