Accessing 4G LTE modem through VPN tunnel

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bouton
DD-WRT Novice


Joined: 12 Sep 2022
Posts: 3

PostPosted: Mon Sep 12, 2022 18:31    Post subject: Accessing 4G LTE modem through VPN tunnel Reply with quote
Hello!
I am using two DD-WRT routers (Buffalo WZR-600DHP2).
One (192.168.2.0) has optical fibre WAN, second (192.168.3.0) has LTE modem in bridge mode connected to its WAN port. This modem has management on http://192.168.4.1
Both routers are connected with openvpn tunnel. And everything is working well.
I have only one issue, I can't solve.
I can access modem managemet from PC connected to second (192.168.3.0) router via its wifi, because it seems router forward http://192.168.4.1 request to its WAN port and modem answer it.
But I can't connect modem management from first (192.168.2.0) router.
How should I setup routes and perhaps firewall that I will get modem management from first router?
Maybe I should first create a route via tunnel to second router?
(route add -net 192.168.4.0 netmask 255.255.255.0 gw 10.0.0.2)
But what is next step? Perhaps on second router? Shoud I add additional route? Should I setup something on iptables? Or should I use port forwarding (I use port forwarding for watching IP cameras on second router from first router)
Thanks for advice!
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egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12812
Location: Netherlands

PostPosted: Tue Sep 13, 2022 10:10    Post subject: Reply with quote
See if this applies: https://wiki.dd-wrt.com/wiki/index.php/Access_To_Modem_Configuration
_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
bouton
DD-WRT Novice


Joined: 12 Sep 2022
Posts: 3

PostPosted: Tue Sep 13, 2022 12:34    Post subject: Reply with quote
egc wrote:
See if this applies: https://wiki.dd-wrt.com/wiki/index.php/Access_To_Modem_Configuration


Hi egc!

This type of configuration work ok on my site.
My problem is, that I have another DD-WRT router connected to internet and both routers are connected with openvpn tunnel.

I can access modem management from router that has modem connected, but I can't access modem management from another router which is connected to first router via openvpn tunnel.
I don't know how to configure route for this case.
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12812
Location: Netherlands

PostPosted: Tue Sep 13, 2022 12:54    Post subject: Reply with quote
Without knowing which side is the server and which side is the client (assuming you have a server/client setup) it is not possible to answer.

Normally there is traffic from client to server but not the other way around.
If you want traffic from server to client you need a site-to-site setup there is a paragraph in the OpenVPN server setup guide about this

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
bouton
DD-WRT Novice


Joined: 12 Sep 2022
Posts: 3

PostPosted: Tue Sep 13, 2022 13:26    Post subject: Reply with quote
egc wrote:
Without knowing which side is the server and which side is the client (assuming you have a server/client setup) it is not possible to answer.

Normally there is traffic from client to server but not the other way around.
If you want traffic from server to client you need a site-to-site setup there is a paragraph in the OpenVPN server setup guide about this


Router A has 192.168.2.0, Optical modem connection to Internet on router WAN port
Router B has 192.168.3.0, LTE modem in Bridged mode for Internet connection on router WAN port

Roter A and Router B are connected with 10.0.0.0 openvpn Tunnel. Router B initiate Tunnel (dial-up).

From devices connected to router A, I can see devices on router A and router B.
From devices connected to router B, I can see devices on router B and router A.
That all works.

I can access modem management (LTE modem on router B WAN port - 192.168.4.1) from devices on Router B, but I can't acces LTE modem management (connected on Router B) from devices connected to Router A.
That is my problem, I don't know how to solve it.
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12812
Location: Netherlands

PostPosted: Tue Sep 13, 2022 16:18    Post subject: Reply with quote
What build are the routers using?

Which router is the Server (I think it is router A)

On the Server did you set a route and iroute command both to the clients LAN subnet and the modems subnet as described in the paragraph about site-to-site setup?

On the client you have to NAT traffic from servers subnet out via the WAN interface/and or the secondary interface if you have made one according to the wiki

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
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