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Not long ago I wrote an article on how to configure an IPsec VPN using Mikrotik and Linux devices. For today, I will replace the Linux device with a Cisco. I did test the entire construct in GNS3 integrated with Mikrotik.

The topology looks like this:

The red line represent the IPsec VPN tunnel.
Please note the used IP addresses. In this way the below configuration will be easier to understand.

Mikrotik Configuration

1. Firewal rules

By default, the Mikrotik comes with the INPUT channel that drop the connection incoming on ether1-gateway (which is the WAN interface). You need to be sure that at least the IPsec packets are able to be accepted inbound on the WAN interface, so the below rules needs to be placed before the rule dropping packets (the Firewal rules are checked top-down)

On INPUT channel allow the following on the interface facing Internet
– Port 500/UDP
– Port 4500/UDP
– Proto 50
– Proto 51
It may be that you don’t need all these ports, but you can close them later. You can check logs if you want to troubleshoot.

On NAT channel, SRCNAT you need have the rule involving interesting traffic (local LAN subnets for example) before NAT masquerade.
You need to add a rule with ACCEPT source LOCAL_LAN (192.168.88.0/24 in this example) destination REMOTE_LAN (192.168.0.0/24 in this example).

On Console the configuration looks like this:

CLI