DSL modem in non-bridge mode and router in DMZ?

[sarotara]

We recently experienced a DSL modem failure and decided to replace both the previous DSL modem we've had as well as the router with a D-Link DSL-520B DSL modem and an Asus RT-AC66U wireless router. We have AT&T as the ISP and had no problems with setting up the DSL modem as a layer 2 bridge and then using the router's PPPoE authentication mode to connect to the outside. The problem with this kind of a setup however, is that the management interface for the DSL modem becomes inaccessible. In bridging mode there are also problems with logging via 514/udp (syslog), something that I was interested in setting up.


I then decided to set up the connection with the DSL modem in PPPoE mode with a 192.168.0.1 IP address on the LAN interface and forwarding all packets to the DMZ host (the router) at 192.168.2.1 (Advanced Setup -> NAT -> DMZ Host). I then went ahead and set the router's WAN port to 192.168.2.1 and it's LAN port to 192.168.1.1. I set the mode on the router to be a static IP address and provided the router with a gateway of 192.168.0.1. The router has DHCP enabled and distributes IP addresses to any hosts connecting to it. The setup looks something like

Internet <---> (DSL Modem WAN (IP assigned by ATT) ::: DSL-Modem LAN (192.168.0.1)) <---> (Router WAN: 192.168.2.1 ::: Router LAN: 192.168.1.1) <---> LAN


The problem with this setup is that while the router says that it is connected to the Internet, it is not possible to connect from any device on the LAN to any external IP address. I'm curious about what silly thing I'm doing here.

 

[Fardringle]

The Asus router's WAN IP address needs to be in the same range as the Modem's LAN IP address. Set the Asus WAN IP address to 192.168.0.2 and its default gateway to 192.168.0.1, and the DNS server(s) to whatever your ISP supplied (or to Google's public servers if you prefer), then forward all incoming traffic on the modem to 192.168.0.2.

 

[sarotara]

Alright, thanks. I'll give it a shot tomorrow and update the thread with the results.

 

[John Connor]

Shouldn't bridging mode solve this? I know the IP addresses are out of range however.

 

[ch33zw1z]

the WAN IP needs to be in the 192.168.0.x range.

I suggest going this route: http://www.ezlan.net/router_AP.html

Make the router an AP, and everything in the 192.168.0.x range.

 

[sarotara]

Fardringle's suggestion resolved the problem:

DSL Modem
- Mode: PPPoE
- DSL WAN: <assigned by ATT>
- DSL LAN: 192.168.2.1
- DSL Modem forwards all traffic to DMZ Host: 192.168.2.254

Router
- Mode: Static IP
- WAN IP: 192.168.2.254
- Default Gateway: 192.168.2.1
- LAN IP: 192.168.1.1

 

[sarotara]

By the way, I really appreciate everyone's help. With respect to John Connor's comment about putting the DSL modem in bridging mode. Yes, I could do that, however the problem is one where if I do this, I am unable to access the management interface for the DSL modem.

 

[kevnich2]

By the way, I really appreciate everyone's help. With respect to John Connor's comment about putting the DSL modem in bridging mode. Yes, I could do that, however the problem is one where if I do this, I am unable to access the management interface for the DSL modem.

Yes but if it's in bridge mode...why do you need to access the web interface? Bridging just puts it in strict layer 2 mode where's there's no filtering, firewall or anything. My experience with any kind of modem is always to bridge it and let the router do it's job.