Help please - setting up a ZyXEL ethernet modem with a DD-WRTed WRT54GL

[ChristopherW]

Right, here goes...

I'm trying to set up a ZyXEL P-660-RU ethernet ADSL modem (cracking little unit, only 20 odd quid too) with a Linksys WRT54GL running DD-WRT v24 (latest stable release). I've got it running 'sorta' at the moment - but it's a bodge. I'm trying to set this up as a secondary network (with a different IP range from the main network) as it'll be used for different purposes - eventually I'm going to try and VLAN it to make life simpler for everyone, but I'm trying to figure out my first problems at the moment!

I have a few odd requirements: the modem (which has a web admin interface) shows as 192.168.2.1 if you plug directly into the back of it (and if you use its in-built DHCP server, you can plug a switch into the back of it and bam: fully-featured routing package, the modem handles all the complexities (NAT/uPnP etc). Unfortunately, it needs to have multiple devices hooked up to it, so the WRT54GL was purchased (and I set it up with a local IP of 192.168.2.2).

However the network's structured, both devices need to be able to be accessed via their web interfaces - I'm not ruling out having the modem on a different subnet entirely, like 10.0.0.1 (and setting up a static route on the WRT54GL), and I've already tried, but I can't get it to work I've tried following instructions on the DD-WRT wiki for setting up a route via iptables and ifconfig (adding commands to the firewall and startup on the WRT54GL) but the VLAN config page on the router confuzzles me greatly, and when I did add the static route rule and made it active (as per the wiki instructions) when I tried to access 10.0.0.1, it just showed the DD-WRT admin page

I tried to set up DD-WRT to handle the authentication, but unfortunately while the modem offers routed or bridged modes of operation, DD-WRT doesn't offer PPPoA, only PPPoE (it's an IPstream MaxDSL service we're on here - no ADSL2+ yet!) I tried configuring the modem and router so that DD-WRT would effectively 'connect' the connection, and the modem just handles the dirty work, but it wouldn't connect whatever I tried.

I then tried setting the modem up with a static IP, disabling DHCP, and setting up the router with a static IP on the same subnet and hooking the modem up to the WAN port on the router - no joy. Doesn't seem to be able to route traffic correctly through the WAN port to the Internet, which is frustrating me somewhat!

I gave up in the end, and as I couldn't get the modem to play nice through the WAN port at all I just hooked it up to one of the switch ports on the WRT54GL and bam! - it works. Unfortunately, this isn't how I want it to work, and it's a bit of a bodge I'm currently running the modem with its DHCP server turned on, and the WRT54GL just relaying DHCP to the modem. The modem itself is handling all the dirty work (uPnP, QoS etc) which is not what I wanted to happen, but as I couldn't get bridge mode working it's the only workaround to get the Internet operational.


What would be ideal (and what I'm trying to aim for) is if the modem is on 10.0.0.1, running in bridged mode and hooked up to the WRT54GL via its WAN port, and the WRT54GL is on 192.168.2.1, handling all of the complex stuff like uPnP, QoS, DHCP allocations etc. I have a similar set up at home with my cable modem router, I hook the cable modem up to the WAN port and set my WRT54GL up to obtain an IP via DHCP - the router takes the public IP and does all the routing on my LAN. Why is it so difficult to make an ADSL ethernet modem replicate the same operation?

I'm trying to avoid the double NAT situation if at all possible! However, at the moment, the only way I can make this connection work is in half-bridge (if it's even that), use the modem to handle some of the NAT and DHCP duties (which is what I wanted to avoid), or have a double NAT. Urgh.

The reason for me being so picky is because this connection is from a business DSL provider and has a higher upstream on it, and it will be running SIP phones (notoriously picky about NATs so I may even port forward a range or set up a port range rule depending on how it works out) and have a few machines on (which are doing a lot of uploading to iTunes and our own web site sporadically, hence the need for flexible QoS and TCP Vegas, which DD-WRT can offer)

If anybody can help me with creating routes in DD-WRT, configuring a network so that router and modem can talk to each other while being on different subnets... Even some info for understanding how VLANs function (and a good tutorial or guide on how to learn the ins and outs so you can progress to setting your own up!) then it's all appreciated.

Cheers in advance!

[ChristopherW]

For the benefit of others, I thought I'd update this thread with a solution - the Petri forums proved invaluable, and this thread documents the efforts myself and a couple of other people put in to get a working solution.

Happy to report that the network now works well, runs stably and does everything I need it to with minimum hassle. Another gold star for DD-WRT! You can read all about it here: http://www.petri.co.il/forums/showthread.php?t=24532 - hope it helps others who are trying to achieve similar setups.

Christopher