Multi-Site Access to Cable Modems with the same ip address

[AllUpSide]

I have two sites connected via a tunnel and both sites have cable modems connecting the site to the internet. Both cable modems have a factory set ip address of 192.168.100.1. See the following diagram.

The edge router at each site has a cable modem interface setup, see here for instructions, to allow users at each site to access that site's cable modem interface. So user 10.10.1.100 can access Site A's cable modem at 192.168.100.1 by accessing 192.168.100.1 and user 10.10.2.100 can access Site B's cable modem at 192.168.100.1 by accessing 192.168.100.1.

How can I change this setup so users at both sites can access both cable modems?

Currently, users on 10.10.1.0/24 subnet can access devices on the 10.10.2.0/24 subnet and vice versa. Is there a way to access Site A's cable modem at a Site A subnet address, say 10.10.1.111 and Site B's cable modem at a Site B subnet address, say 10.10.2.111?

Thank you.

[lleachii]

@AllUpSide

How can I change this setup so users at both sites can access both cable modems?

Make a Port Forward (redirect) rule for Site A hosts to reach the 192.168.100.1 addresses at the Site B, and vice versa.

(Same method can be used on the OpenWrt itself if all routers were still using the default LAN IP.)

[AndrewZ]

Make each local modem accessible through port forwarding on the local router, then forget about duplicate modem addresses.
The rule could be similar to what I posted in Mikrotik Router device switch ports - #8 by AndrewZ

[AllUpSide]

Sorry, I’m not familiar with reirects.

Each site router has an interface like this:

So users at each site access their cable modem with the same address 192.168.100.1.

How do I create a redirect if the destination ip address is the same for both modems?

[lleachii]

@AllUpSide

How do I create a redirect if the destination ip address is the same for both modems?

• You'd use an IP on the networks devices that are not the same (e.g., 10.10.1.1 and 10.10.2.1)
• Alternatively, assign an additional IP to use for the Port Forward

@AllUpSide

say 10.10.1.111 and Site B's cable modem at a Site B subnet address, say 10.10.2.111?

Or create the redirects based on these - this works too.

[AllUpSide]

I tried this and it addressed my issue. Please note that it didn’t appear to work at first, but one of rebooting the router, clearing the browser cache, or deleting the original modem interface resolved this. The cable modem status page is now available at: http://myrouter.ipaddress:3333

/etc/config/firewall entry:

config redirect
        option dest 'wan'
        option target 'DNAT'
        list proto 'tcp'
        option src 'lan'
        option src_dport '3333'
        option dest_ip '192.168.100.1'
        option dest_port '80'
        option name 'Modem access'
        option family 'ipv4'

Luci view:

[AllUpSide]

Thank you for your help and follow-up; I now have a new network skill.