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## **Tutorial: Bridging the D-Link DSL-6850U for OpenWrt (Bezeq Infrastructure)**
### **1. Modem Configuration: Creating the Bridge**
In the modem's web interface (typically `10.0.0.138`), you must define the correct Layer 2 transport.
* **Interface:** Choose **PTM** (Packet Transfer Mode). Avoid ATM, as it is for legacy ADSL speeds (below 15Mbps).
* **Service Type:** Select **Bridge**.
* **VLAN Settings:** Set **VLAN ID** to **-1** and **Priority** to **-1**. This creates an "Untagged" service.
* **Logic:** By using `-1`, the modem acts as a transparent media converter, allowing your OpenWrt router to handle the raw data.
### **2. The Problem: LuCI Management Interface Conflict**
If you attempt to add a Management Interface (to access the modem's GUI) using the OpenWrt web interface (LuCI), it often breaks the connection.
* **The Symptom:** Internet drops immediately, and logs show `PADO Timeout` or `Unknown error (USER_REQUEST)`.
* **The Cause:** LuCI's backend often creates a software bridge or changes the `wan` device state in a way that blocks PPPoE discovery packets from reaching the modem.
### **3. The Solution: CLI Configuration**
To gain access to the modem while keeping the internet alive, "side-load" the management interface via SSH. This method allows the physical `wan` port to carry two logical streams: the PPPoE tunnel and a Static IP.
Run these commands in order:
```bash
# 1. Define the Management Interface on the physical 'wan' port
uci set network.modem_mgmt=interface
uci set network.modem_mgmt.proto='static'
uci set network.modem_mgmt.device='wan'
uci set network.modem_mgmt.ipaddr='10.0.0.1'
uci set network.modem_mgmt.netmask='255.255.255.0'
# 2. Prevent the interface from overriding your internet route
uci set network.modem_mgmt.delegate='0'
uci set network.modem_mgmt.metric='40'
# 3. Commit changes and link to the WAN firewall zone
uci commit network
uci add_list firewall.@zone[1].network='modem_mgmt'
uci commit firewall
# 4. Reload services
/etc/init.d/network reload
/etc/init.d/firewall restart
```
**Verification:** You should now be able to browse to `http://10.0.0.138` while your OpenWrt `wan` interface remains connected to the ISP.
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