Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

My home network connects to my ISP through an ADSL modem/router in bridged mode. I have the following setup:

|
ADSL modem/router, bridged mode
|
| x.x.x.x public IP on WAN interface
Router with DHCP server
|192.168.0.1
|
LAN and WLAN

several devices with dynamic IPs 192.168.0.100 - 192.168.0.200

In this setup I can't access the web interface of the modem/router, since it has no IP. If I assign it a static IP 192.168.0.5, it's not reachable. If I assign it a static IP 192.168.1.5 with netmask 255.255.0.0, it's not reachable either. I suspect the router wraps all packets to foreign IPs and sends it over the modem/router-bridge without ARP'ing the network at the WAN interface of the router.

Now I make a connection between the Router LAN interface and the Router/Modem LAN interface, between point X1 and X2. This occasionally works, but sometimes it happens that the router gets an IP of its own DHCP server, the network ends up in infinite recursion of packets,... All understandable in this setup, BUT I can access the modem/router web interface.

|
ADSL modem/router, bridged mode
|192.168.0.5
|
|----------...X1
|
| x.x.x.x public IP on WAN interface
Router with DHCP server
|192.168.0.1
|
|----------...X2
|
LAN and WLAN

several devices with dynamic IPs 192.168.0.100 - 192.168.0.200

share|improve this question

closed as off topic by Bryan, Magellan, John Gardeniers, Ladadadada, Iain Nov 26 '12 at 14:37

Questions on Server Fault are expected to relate to professional server, networking, or related infrastructure administration within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

2 Answers 2

First of all, the ADSL modem would need a static IP address that is on a different subnet than the internal side of the network, so something in the 192.168.1.x range would work. The netmask should be 255.255.255.0. All of the clients on the inside of your network (192.168.0.x) also need netmasks of 255.255.255.0. I would think that this setup alone should work. From what you have described, we have a setup exactly like this, which works well.

share|improve this answer
    
All client inside my network have a netmask of 255.255.255.0 The ADSL Modem indeed had 255.255.0.0, I changed it to 255.255.255.0 but it still cannot find 192.168.1.5. I sniffed the network on the ADSL Modem side but there are no ARP's for 192.168.1.5 A traceroute shows me: 192.168.0.x 192.168.0.1 192.168.0.1 (twice in list) ISP gateway IP –  user16043 Aug 9 '09 at 11:18

If your modem is recent, it's address is probably 192.168.1.254/255.255.255.0. If you set the ip of the interface connected to the modem to 192.168.1.1/255.255.255.0 you should be able to access the modems web interface.

Some older ADSL modems, such as the GNET BB006x series used an ip of 192.168.7.1/255.255.255.0.

Take note, if you received your modem from your ISP preconfigured, they may have changed the ip address and or password used by the modem.

share|improve this answer