Accessing a DSL Modem Through a PPPoE Interface
Most modems have a web interface available, but once an interface is configured as PPPoE, you can no longer access this interface. There is a way of accessing it and it is quite simple.
Creating the Virtual IP
In order to do this you need to know the interface name which is connected to the PPPoE interface. If you don't know it, do a:
grep ETH /etc/sysconfig/network-scripts/ifcfg-ppp*
In my case it is enp2s0.
You also need to know the Modem's IP address and subnet, and preferably its DHCP range if it is running a DHCP server. Mine is 192.168.2.1/24 and 192.168.2.10-192.168.2.210. From this choose a LAN IP in the same subnet but outside the DHCP range and not the modem IP address and not the last address in the subnet (typically a .255 address). I have chosen 192.168.2.2. Now you need to add an IP address to your interface:
ifconfig enp2s0:0 192.168.2.2 netmask 255.255.255.0
Note the :0 on the end of the interface name
To make it permanent, you can add it to /etc/rc.d/rc.local and make the file executable (instructions are in the file).
You also need to add a firewall rule:
iptables -t nat -I POSTROUTING -o enp2s0 -d 192.168.2.0/24 -j MASQUERADE
To make it permanent, add it to teh CUstom Firewall, but like:
$IPTABLES -t nat -I POSTROUTING -o enp2s0 -d 192.168.2.0/24 -j MASQUERADE