Router Configuration - port forwarding

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View
Hi all,

My home setup is somewhat silly, but it is the way it is since we're
sharing a cable connection between houses and don't want to buy new

We have the cable modem feeding into a netgear wgt624 router. This
connects one computer and then sends out a line which feeds into our
linksys BEFSX41 router.

This linksys router then connects two computers.

The setup works fine, and quickly for internet browsing, downloading,
and uploading.

The problem I'm having is with connecting a VOIP box to this second
router to make calls. I can make calls but I lose them after about 30
seconds, pretty consistently.

My VOIP company suggested this:

If you have a router before the adapter, please make sure you have
69;5060-5063; 10,000-20,000UDP forwarded in your router configuration
the IP address of your device. You can also put the phone adapter in
DMZ (demilitarized zone) of your router.

I would understand how to do this if the chain was modem->router->VOIP
box, but since it's actually modem->router->router->VOIP box, I'm a bit

Right now, both routers are using DHCP and all IP addresses are
generated automatically.

My question is, assuming the first router will stay as DHCP, how do I
configure the whole thing?

Should I be activating the port forwarding in the first or second

Will I need a static IP for the second router or just for the computers
and VOIP box connected to it?

What about DNS, subnet and gateway?

I have DNS numbers, just not sure what to do with them exactly.

Many thanks to anyone who gets this and can give me a hand. I hope this
is the right place to post this. If there's a better spot, I'd
appreciate some redirection.

Thanks very much,

Re: Router Configuration - port forwarding wrote:
Quoted text here. Click to load it

There is a diagram of double port forwarding here:

I've seen a picture of one VOIP device, that seemed to be
set up to be first in the chain (a WAN and a LAN connector
on it). It would thus get the ports it wanted, and pass
the rest of the traffic to the home router. What I don't
know about such a config, is if the VOIP device is secure
enough to be exposed to the Internet like that. Does your
VOIP only have the one Ethernet connector on it, implying
it is a leaf for the lowest level in your network ? All
that port forwarding makes me dizzy.


Re: Router Configuration - port forwarding

On 17 Oct 2006 11:50:37 -0700, wrote:

Quoted text here. Click to load it

First, do you need the second router, to route at all?
Is it necessary to segregate your lan from your neighbors?
Perhaps so, or perhaps there are advantages to both being in
the same lan- I don't know your neighbor or needs.

If the shared lan is acceptible, simply use the switch in
your router, not connecting to the WAN port on your router,
and then port-forwarding is handled by only the router
actually routing.

Quoted text here. Click to load it

Set the port forwarding on the first router to point to the
second router's WAN IP address.  In the second (your)
router, set it's port forwarding to the IP address of the
VOIP box or the computer it's connected to if it is a host
controlled device.

If you do away with routing via the 2nd router as I
mentioned above, set the first router to forward those ports
to the IP of the VOIP box or host (computer) system.

Quoted text here. Click to load it

I recommend a static WAN IP address for your (2nd) router.
You can set that in your router, or sometimes, in the first
router you can assign the fixed IP address to the MAC
address of the WAN port on your, 2nd router.

Quoted text here. Click to load it

You cannot have it randomly assigning a different IP address
via DHCP, unless you are willing to change the forwarding IP
address in the first router every time that first router
assigned a different IP address to the WAN port on the
second router.

Quoted text here. Click to load it

Yes both of them, see above.

Quoted text here. Click to load it

I had assumed the VOIP box had a static address, or at least
that could be permanently fixed.  If it can't, then you do
on the second router as I'd described on the first, have it
always hand out the same IP address for the VOIP box - OR -
the host system that VOIP box is attached to if the host
system is the holder of the IP address.

Quoted text here. Click to load it

If you manually configure the settings, you will have to
specify these.  If you set the router(s) to always hand out
the same IP address to a certain MAC address (on the first
router, reserve an IP address for the WAN port on the second
router, and on the second router, reserve an IP address for
the host system the VOIP box is connected to, or the VOIP
box itself.  Thus, if the routers can set static IP
addresses via MAC addresses, it is slightly easier and
quicker.  Some routers will even show a list of MAC
addresses connected to it's LAN (which for the first router,
will also include the MAC address of the WAN port on the 2nd
router, in a list so you can simply choose it instead of
having to consult the (usually a lable) on the device to get
that MAC address).

Quoted text here. Click to load it

The DNS numbers are always the same on every router.  You
could let the 2nd router get the from the first, or program
them in yourself.  Whatever they are, the purpose of the
router is to route to them, they merely need to be the
correct numbers as supplied by the ISP for their service,
whether you get them from the ISP's DHCP service, or type
them in on any or all equipment in you and/or your
neighbor's equipment.

Site Timeline