[nflug] Router Questions

[kobear at sharedbrain.net]

Quoting "David J. Andruczyk" <djandruczyk at yahoo.com>:

>
>
> --- Joe <josephj at main.nc.us> wrote:
>
> > I understand what a router is, but I've never worked with one, so
> > I've
> > got some basic questions.  I don't expect anyone on this list to
> > debug
> > my VoIP (SunRocket) problem.  The questions below are mostly OS and
> > vendor independent.
> >
> > I'm having trouble getting VoIP to work for my partner (I'll be
> > talking
> > to VoIP level 3 support later.)  She has Verizon DSL.  I don't
> > remember
> > the exact speeds, but it's about 800/168 (the slowest/cheapest).  The
> >
> > VoIP says it needs 90/90 to work.
> >
> > Currently, the DSL line comes into the Modem, out to the VoIP box,
> > and
> > then from the VoIP box into the notebook (Win 98se). Nothing has
> > wireless capabilities.
> >
> > When I hook up the DSL without the VoIP box, it works fine.  When I
> > put
> > the VoIP in the middle,  not only does it not work, but the DSL goes
> > away and when I remove the VoIP box, I have to argue with the DSL box
> >
> > for awhile to get it to work again.
>
> Solution.  Install in sequence below:
> DSL line -> DSL modem-> VoIP box - >Laptop
>
> power off all device (INCLUDING the dsl modem)
> power up DSL modem,  wait till all lights on it say it's ready and
> working,   power up Voip box make sure it becomes "ready",  then power
> up laptop, and all should be working correctly now.  Make sure the
> laptop is configured for DHCP. (almost all are).
>
> Reason:  DSL and cable modems detect the MAC address of the device
> directly plugged into them (whether it be a router, computer, appliance
> device, etc), and refuse to accept traffic from any other MAC address
> unless powercycled.    MAC addresses do NOT cross router boundaries
> (read up on the OSI model if you really want to know why). The Voip box
> is essentially a simple router device with added gee-whiz stuff inside
> (the voip crap).
>


Actually, I think he said that he never had the DSL router not be the first
device facing the DSL network.  If that is the case, then the MAC address would
not change.

I think that what is going on here is that you have a IP address
conflict/overlap the two networks.

Let's take a standard out-of-the-box config.  Most routers plant the internal
addresses on the 192.168.1.x network.  If both the DSL router and the VOIP
router are doing this, then you have the following kind of problem:

DSL Line (Public IP's) -->  DSL Modem (192.168.1.0/32 or 192.168.1.1) --> VOIP
Router (192.168.1.0/32 or 192.168.1.1) --> Internal network (192.168.1.0/24).

Notice that both routers think that their address is 192.168.1.1.  When the VOIP
router gets traffic that it does not know what to do with, it is supposed to
hand it off to it's default gateway, which is the DSL modem.  But since it has
the same IP address as the modem, it cannot find a route to it, and therefore a
routing loop is created.

Given this, most verizon routers can be setup in Bridged mode, thereby the VOIP
router can be given the public IP address for its WAN port and the problem is
likely solved.

HTH,

Kyle


>
>
>
> Dave J. Andruczyk
>
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