Hello .I have isp router with pppoe and subnet 192.168.1.0/24 gw 192.168.1.1 .on this isp router i have 1 pc with ip 192.168.1.110 .on ether 3 of isp router i have a mikrotik with dhcp client and with subnet 172.168.1.0/24 gw 172.168.1.1 and on ether 2 of mikrotik i have a dvr with ip 172.168.1.200.i cant see this ip from my computer because of subnet . how can i donthat please?

Add a route on the ISP router that sends traffic destined for 172.168.1.0/24 to ether3. You may need to enable proxy-arp on the Mikrotik interface connected to ISP router port 3.

You could potentially also add a static route on your PC for 172.168.1.0/24 pointing at the public interface of the Mikrotik router. It doesn't scale well, but it can work.

It would be better for your Mikrotik to have a static IP or DHCP reserved IP from the DHCP server, but you may or may not be able to easily do that.

First of all don't use 172.168.1.0/24 because is an Public Subnet not a private one, use 172.16.1.0/24