Laforet

I am fed up with my Netgear DG834Gv4 all-in-one router. The built-in switch crashes too often and is now a major annoyance to reboot the router twice a day. I read on OCN some time ago that if you dial from another router and uses your ADSL router only as a modem it helps. But my ISP uses PPPoA, is it possible to pass the traffic through to another router?

__________________
FYI:
1. No LLC or volt-mod for 24/7.
2. Windows 7 is Vista in disguise, you are better off with the latter before Windows 7 SP1 comes out.
3. For 45nm silicon, 1.45V in Vcore is not unsafe, however 1.3V in Vtt already is.
4. LGA1366 for SLI/CF.
5. Performance Enhance to Standard for memory issues on Gigabyte boards.

pippolo

The main question is what of the 2 devices (the modem and the new router) will manage the NAT job.
My old Netgear DG834PN (like a lot of other brands of router) have the well known problem about the NAT table. When you use a lot of connections (using the p2p, ad example) the NAT table fills up and when full, the router starts to loose connections and the speed goes down.
It was necessary to reboot the router every day (mine was a NAT problem, not a switch problem).

The solution was to buy a good router to do the NAT job and leave only the modem task to the old Netgear.
But my ISP permits only PPPoA and if you connect a modemless router to an ADSL modem (connected in 'full-bridge') you need PPPoE between the two devices (is the new Router that has to manage the NAT and have to know the external IP address, so it's necessary that all the ISP authentication protocol is done by the router).

The only solution was to use the so-called 'half bridge' configuration.
Pratically, the modem manages the ISP authentication protocol and does only a basic NAT (1:1). It gives to the router the external infos (IP, DNS) using a DHCP protocol and the router does all the rest (NAT, Firewall, routing, etc.).

The main problem is that there are a lot of incompatibilities between modem and routers regarding the 'half-bridge' protocol, and it's very difficult to find a router capable to talk correctly with the ethernet modems.

Here you can find some discussions about half-bridge.

I resolved the problem buying a cheap ADSL ethernet modem (Netgear DM111P) configured in half bridge and using a Mikrotik RB433AH semi-professional router.

A friend of mine configured his router in order to use it with the same router. He configured the router in this way:

- the new router does all the firewall job and also the NAT between the internal network (ad example 192.168.0.x) and a single external address like ad example 192.168.1.1 (the address of the external router port)
- the default gateway is 192.168.1.2 (the gateway of the router... the PC gateway will be the internal port router address)

the old router is configured in this way:
- internal address as 192.168.1.2
- Firewall disabled
- DMZ enabled and default DMZ address specified (it's possible specify a default address to send every packet not already destined to other addresses). The default address is 192.168.1.1
- ADSL login settings managed by the modem
- NAT enabled (but it translates only between the external IP and the single 192.168.1.1)

The only remaining problem is the DNS. If you use the ISP dynamic DNS address, you need a way to pass it from the modem to the router. A solution is a double jump. The modem acts as a DNS server, the router also acts as a DNS server, but sends the requests to the modem. All the PC uses the router as a DNS server.
Another solution is to creates a route on the router from the internal network to the router address. In this way, you can assign the modem address (192.168.1.2) as DNS server on every PC and you don't need any DNS functionality on the router.

Laforet

KUDOS to you, signore. This is the most practical solution I have been given so far. +rep

Mine is indeed a switch problem, I can still connect via its wireless access while the switch lay dead. I suspect if I use it as a modem it will not help because the same amount of packets will have to get through that switch anyway, time for a new modem I still wish they have made a half-decent ADSL2+ internal modem so I can just build a router box....

Oh one last thing, in this scheme where essentially two routers are present, does it mean port forwarding has to be set up on both devices?

__________________
FYI:
1. No LLC or volt-mod for 24/7.
2. Windows 7 is Vista in disguise, you are better off with the latter before Windows 7 SP1 comes out.
3. For 45nm silicon, 1.45V in Vcore is not unsafe, however 1.3V in Vtt already is.
4. LGA1366 for SLI/CF.
5. Performance Enhance to Standard for memory issues on Gigabyte boards.

pippolo

No. The first solution (the solution used by me) require an ethernet ADSL modem configured in 'half-bridge' and a router (without modem). The second requires also the router, but as modem you can use an ADSL router (a router+modem) with the router part unused.

In the second solution, the router that acts as a modem has the firewall disabled because it sends all the unrecognized incoming packets (if you don't define any port forwarding, all the incoming packets are 'unrecognized') to a default IP that is really the IP of the incoming port of the second router (you can define a 'default' IP in the DMZ section of your router).

So, the first has virtually all the ports forwarded to the second. The second has to do all the firewall job.

The first solution (true modem) is better because it hasn't to do the NAT job, but the second solution is cheaper (if you already have an ADSL router).

At first I tried the second solution (a new Mikrotik router as main router and the old Netgear used only as a modem). After I bought a true modem (Netgear DM111P) capable to do the 'half-bridge' trick and switched to the first solution.

About your problem... if you want build a router from a PC it's possible using the first solution. You needs only to buy an ethernet modem and a PC (an old spare PC is ok) with 2 NIC. The 'half-bridge' trick needs only a router capable to gets his external address using DHCP (and manage the DHCP lease) and the ability to cope with a default gateway outside of the netmask of the interface (about this read the 'LINUX STATIC ROUTE FIX' note on the link)