Re: 2wire 'router behind router' error

Voytek,

Answers in line below.

Regards, Martin

[email protected]


On Fri, May 29, 2009 at 12:09 PM, Voytek Eymont <[email protected]> wrote:

> few month ago I connected to BigPond ADSL2+;
>
> the LAN has 2wire ADSL on 192.168.1.254
> Linksys 3102 (.3) and Linksys 2100 (.2) on fixed IP bridged;
> one XP on fixed IP;
> one intermittent XP on DHCP;
>
> this morning any URL (except Bigpond) diverted to:
>
> http://gateway.2wire.net/xslt?PAGE=HURL08
>
> which is the ADSL modem/router and it said [1] "Router Behind Router
> Detected Error"
>
> the 'gateway.2wire.net' resolves to 192.168.1.254
>
> Q: how does the gateway.2wire.net resolves to 192.168.1.254?
> is that in 2wire router DNS?
>

This can be done a number of ways. Most home routers implement a basic
caching DNS. All this DNS process needs to do to implement the above is to
basically create a dynamic A (address) record for gateway.2wire.net that
points to the router's own LAN address. (This will be the case if the DHCP
server on the router also sets your workstation' DNS to point to itself) The
other way it might do this  is to implement basically a transparent DNS
proxy that intercepts any DNS queries for a gateway.2wire.net and return an
answer (possibly lying that it actually came from a real DNS). This would be
done if you don't use the ADSL router as a DNS, but just configure your
machines to resolve to your ISP or other DNS. (Some enterprise-class boxes
,Packeteer and Netscaler I know of,  implement this "feature" to aid
configuration without having to manually configure IP addresses for the
initial setup).


>
> it seems quite nifty, when there is no conectivity, it diverts to router;
>
> how would I set such with an arbitrary router, to divert to it on failure ?


This would be implementation dependant on the 2wire router software

>
>
> Q: what could have caused this 'router behind router' error, intermittent
> glitch ? it's 'gone away' now


Presumably it has received a packet from your LAN with a source address that
is not in the 192.168.1.0 network (and as you have indicated below, it is
probably your bluetooth interface). The only logically conclusion that the
ADSL router can make is that there is something on your network acting as a
router. The problem for your 2wire router is that unless you tell it where
that network is then it has no "next hop" to send it to. Most routers (even
home routers) allow you to setup a static route to allow this. The ADSL
router would then need to NAT this as well when it needs to send packets to
the Internet. It seems that 2Wire is trying to be "smart" about doing this,
but not having seen this box, I can't really comment on what it actually is
doing.


>
>
> the XP machine has a bluetooth dongle on 192.168.0.1, and, routing enabled
> on LAN NIC for the bluettoth, is that a likely culprit ? (but IPs are
> manually assigned)


Yes that would be it.

>
>
>
> [1]
> Router Behind Router Detected
> Error
> The Connection Monitor has detected a third party router connected to the
> 2Wire Gateway.
>
> If you want to connect additional computers or devices to your network:
>
> Click the Resolve button below to enable the Connection Manager to correct
> the problem. There may be a delay of up to one minute while the Connection
> Manager resolves the problem.
>
> Click the Disable button below if you want to continue using your Router
> behind Router.
> WARNING: Many applications may not work in this case.
>
> For detailed information regarding this issue, please click on the link
> below:
>
>
> Router Behind Router Detection
> The Connection Manager has detected a third party router connected to your
> 2Wire Gateway. This creates a condition where two routers each attempt to
> manage devices behind a NAT. This can create instability in your network
> and affect performance.
>
> The Connection Manager can assign your third party router to DMZ Plus
> Mode. This will allow both the 2Wire Gateway and third party router to
> share the same public IP. Follow the instructions on the previous page to
> assign your third party router to the DMZ.
>
> If you need to share devices within a network, the recommended solution is
> to attach a switch or hub to your 2Wire Gateway, and connect devices from
> your network to the switch. In this configuration, the NAT capabilities of
> your 2Wire Gateway will assign private IP addresses to the connected
> devices, and allow those devices access to the internet via the public IP
> issued by BigPond.
>
>
>
> --
> Voytek
>
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