[wellylug] ADSL modem and Linux router/firewall without double NAT

Daniel Reurich daniel at centurion.net.nz
Thu Jan 7 19:27:51 NZDT 2010

Just to document this for those who wish to try it.

To enable the half Bridge mode on the dynalink rta1320E when using a
telecom based PPPoA adsl service.

1) connect up the modem as per usual, and log in to the web interface at

2) Select "Advanced" at the top of the page.
3) Select "Internet" in the menu on the left side of the page.
4) Select edit for the first (and probably only) PVC connection, and
select next x2 to get to the relevant page, 
5)Untick the "Enable NAT" box
6)Tick the "PPP IP extension" box,
7)Select next,
8)Fill in your username and password details if not already done.
9) Select finish and the modem will reboot.
10) Once the modem has rebooted, the connection should come up and
assign the real connection IP address, dns etc via dhcp. 

Note: To access the modem you will need to add 192.168.1.X (where X is 2
or higher) to your routers external interface via an alias.
(eg eth0:0

And then all routing, nat, QoS etc is handled by your pc based router.


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