Bypass Router to connect to modem

Question

The network has 2 subnets:

         i) 192.168.1.x 
         ii) 192.168.100.x 

The telecom optical modem sits at 192.168.1.1

A cisco router and windows server are present on the network. DHCP and DNS (192.168.100.200)services are provided by these.

I dnt want to change any config on either of these. I have DVR which i would like to put online and need ports forwarded.

I am trying to connect the DVR directly to the ethernet port on the modem.

I have tried with my laptop. Unless i use the the internal dns(192.168.100.200) i cannot get access to internet. this however means my laptop ip address also needs to be in same subnet. But now i cannot access the modem from this IP.

Any suggestions on how I may setup ?

The model is : Huawei HG8245H Router is Cisco 1941-K9

Answer 1

Assuming that the Huawei ONT is the only WAN gateway.

You'll need a router to connect both subnets. If you can't/don't want to change either the ONT's or the Cisco's config/address you'll need another router.

You could use the Windows server with routing activated and an address from each subnet on the NIC. However, with a router in between, the ONT would require a route back to the 192.168.100.0/24 subnet.

You could also reduce the subnet mask to /16 so everything becomes local but then again, you'd need to do that on both the Cisco and the Huawei as well...

Zero config change could only be done with source NATting from 192.168.100.0/24 to 192.168.1.0/24 and that would be really ugly.