[LogicallySkewed]

First, here is my current setup:

ISP Modem
Has no routing capabilities
Gets non-static IP address from ISP

Router 1 (no VPN)
Router: Linksys EA9200
Firmware: Linksys (DD-WRT not compatible)
WAN port connected via cable to ISP Modem
Local IP: 192.168.1.1
Subnet Mask: 255.255.255.0
DHCP enabled, IP range: 192.168.1.100 to 192.168.1.149
NAT,
IPv6: Disabled
Static Routes: None currently set up

Router 2 (VPN)
Router: Linksys WRT3200ACM
Firmware: DD-WRT
WAN port connected via cable to LAN port of Router 1
VPN: NordVPN set up through OpenVPN
VPN Passthrough: Enabled
WAN IP: 192.168.1.148
Local IP: 192.168.2.1
Subnet Mask: 255.255.255.0
DHCP enabled, IP range: 192.168.2.100 to 192.168.2.149
Operating Mode: Gateway
IPv6: Disabled
Static Routes: None currently set up

I can connect to the Internet when connected to either router. I can also connect to devices on Router 1 when I am connected to that router and the same for Router 2, but I cannot connect to devices on Router 1 when I am connected to Router 2 and vice versa. Further, I can connect to devices on Router 1 when I am outside my network but not to devices on Router 2. I've searched for a solution but haven't found anything that has worked. I've also talked to tech support at NordVPN and they inform me that port forwarding isn't supported by their VPN. I figure there has to be a way to get this to work though. What do I need in order to connect to devices on each router when connected to the other? What do I need to connect to the same devices when outside of my network?

Thank you very much in advance! Any help would be greatly appreciated.

[LogicallySkewed]

I tried that previously and it didn't work . Router mode on the VPN router seems to kill my connection to the Internet when I am connected to that router.

[Per Yngve Berg]

Why don't you swap router 1 and 2?

On router 1: Enter static route to 192.168.2.0/24 gateway 192.168.1.148

Note: I would have used a static IP 192.168.1.2 for the WAN on router 2.

[egc]

First of all it is good practice to also state your build number, some builds can have problems ( )

You can not do anything on your ISP modem does that mean it is in bridge mode?
In that case the WAN ip of router 1 should have a public IP, is this the case?

In this kind of setup you should be able to reach router 1 (and its clients) from clients on router 2 even if it is using a VPN.
If not then show output of:

[LogicallySkewed]

Thank you, egc! I was using a kill switch and turned it off. After following the instructions, I've managed to get connectivity to the devices between each router. I haven't looked through everything yet to see about getting remote access when I am not in my network, but will let you know.

The kill switch I was using was recommended by my VPN provider:

WAN_IF=`nvram get wan_iface`
iptables -I FORWARD -i br0 -o $WAN_IF -j REJECT --reject-with icmp-host-prohibited
iptables -I FORWARD -i br0 -p tcp -o $WAN_IF -j REJECT --reject-with tcp-reset
iptables -I FORWARD -i br0 -p udp -o $WAN_IF -j REJECT --reject-with udp-reset

Is there a different way I can do a kill switch that won't break my connection between each router?

[Per Yngve Berg]

WAN_IF=`nvram get wan_iface`
iptables -I FORWARD -i br0 -o $WAN_IF -j REJECT --reject-with icmp-host-prohibited
iptables -I FORWARD -i br0 -p tcp -o $WAN_IF -j REJECT --reject-with tcp-reset
iptables -I FORWARD -i br0 -p udp -o $WAN_IF -j REJECT --reject-with udp-reset
iptables -I FORWARD -o $WAN_IF -d 192.168.0.0/16 -j ACCEPT


Added a accept for the local LAN.

[egc]