Internal Layout D-Link DIR-825

This article describes the internal layout and configuration of the D-Link DIR-825. This particular hardware has two physical network interfaces, eth0 and eth1, whereas most emebedded devices have only one: eth0. It also has two two wireless network interfaces using the IEEE 802.11 protocol, represented by wlan0 and wlan1.

iface	Port
eth0	internal interface connected to Gigabit Switch (default)
eth1	internal interface connected to WAN port (default)
wlan0	radio0
wlan1	radio1
usb	Bluetooth/3G/etc.

Additional information on the rtl8366s switch. Switch 1: rtl8366s(RTL8366S), ports: 6 (cpu @ 5), vlans: 16 (4096 starting with 10.03.1-rc4)

switch port id	Label on the back
port:0	LAN4
port:1	LAN3
port:2	LAN2
port:3	LAN1
port:4	WAN
port:5	internal

The default config provided looks something like below:

config interface loopback
        option ifname   lo
        option proto    static
        option ipaddr   127.0.0.1
        option netmask  255.0.0.0

config interface lan
        option ifname   eth0
        option type     bridge
        option proto    static
        option ipaddr   192.168.1.1
        option netmask  255.255.255.0

config interface wan
        option ifname   eth1
        option proto    dhcp

config switch rtl8366s
        option enable   1
        option reset    1
        option enable_vlan 1

config switch_vlan
        option device   rtl8366s
        option vlan     0
        option ports    "0 1 2 3 5"

Going through the configuration, step by step, provides the following information.

First there's the loopback interface lo.
Second, in this configuration, eth0 is part of the bridged interface lan.
Third, eth1 is configured as the wan interface.
Fourth, is the switch configuration.
The 'config switch rtl8366s' options enable the switch, reset it and enable VLAN capability.
The 'config switch_vlan' options enable VLAN0 and assigns it to the 4 external LAN ports and internal eth0 interface.

Note: The eth1 network interface is assigned to VLAN1 by default, which in turn is assigned to switch port 4 by default. Further, eth1 is also configured to be part of the virtual interface wan. Configuring wan with a static ip address will provide another avenue to access the router using SSH. Finally, either of the wireless interfaces can be configured to enable wifi access as well.