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RT31P2 - How to get a static IP address on LAN

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Anonymous
August 25, 2005 11:01:12 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

I have the following configuration:

Cable Linksys DLink Wireless
Modem ------ RT31P2 -------- DI-604 -------- Router ------- PCs
NAT & DHCP Router | no NAT
| no DHCP
|
|---- Desktop PC

I'd like to configure the Desktop PC as an FTP server and I have setup
port-forwarding on the RT31P2 and the DI-604 routers. It works except
that the DI-604 sometimes gets another IP address from the RT31P2 and
causes the port-forwarding to no longer work because the IP address
of the downstream router has changed.

The RT31P2 sits in front of the DI-604 because the RT31P2 is for voip
service and it gives voice traffic priority over other traffic (QoS).

The DI-604 has a static DHCP function that allows me to tie the Desktop
PC
to a specific address on the DI-604. The static DHCP keeps the Desktop
IP
address constant.

Is there a way to keep accomplish this?

It would be great if the RT31P2 had static DHCP - perhaps there's
another way
to accomplish the same function.

Can I configure the DI-604 to have a static address and turn off
DHCP/NAT on the
RT31P2? A static WAN address on the DI-604 requires I define also DNS
server addresses
and I'd like to keep getting those automatically.

Any other suggestions?

Chris
cjtwantstoknow
Anonymous
August 25, 2005 12:36:57 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

On 25 Aug 2005 07:01:12 -0700, cjtwantstoknow@yahoo.com wrote:

>I have the following configuration:
>
>Cable Linksys DLink Wireless
>Modem ------ RT31P2 -------- DI-604 -------- Router ------- PCs
> NAT & DHCP Router | no NAT
> | no DHCP
> |
> |---- Desktop PC

This is the first time I've ever seen anyone try to use *THREE*
routers in series. Is there some reason you think you need the extra
two routers? The RT31P2 is an ethernet router with all the features
that the other two routers duplicate (except wireless).

Start by removing the DI-604. It does nothing useful.

Then, reconfigure the Wireless Router (no model number specified) into
an access point. Do not connect anything to the WAN port. Setup the
IP address to be in the same /24 group as the RT31P2 but on a
non-duplicated IP address. Disable the DHCP server. Now, it's just
an access point.

Plug the PC's and Desktop PC into the RT31P2 LAN ports.

>I'd like to configure the Desktop PC as an FTP server and I have setup
>port-forwarding on the RT31P2 and the DI-604 routers. It works except
>that the DI-604 sometimes gets another IP address from the RT31P2 and
>causes the port-forwarding to no longer work because the IP address
>of the downstream router has changed.

Well, if you insist on using the DI-604, dive into the RT31P2 and see
if it has a feature called "static DHCP". If so, configure it to give
the MAC address of the DI-604 router always the same IP address. I
couldn't find anything in the manual at:
ftp://ftp.linksys.com/pdf/rt31p2_ug.pdf
that would indicate that it has this feature. The only alternative is
to assign a static IP address on your desktop PC that's acting as an
FTP server, and port forward the RT31P2 to point to this static IP
address. Please pick an IP address that is NOT inside the DHCP
assigned IP address range of the RT31P2.

>The RT31P2 sits in front of the DI-604 because the RT31P2 is for voip
>service and it gives voice traffic priority over other traffic (QoS).

Yes, the RT31P2 *MAY* be installed in front of an existing router.
However, there's no reason why it must be installed in front of this
router. The recommended setup in the manual does not show the extra
router. The RT31P2 duplicates all the functions of the DI-604 with
the added complexity of dealing with two routers. There's no need to
do that. Just use the RT31P2 and sell the DI-604.

>The DI-604 has a static DHCP function that allows me to tie the Desktop
>PC
>to a specific address on the DI-604. The static DHCP keeps the Desktop
>IP
>address constant.
>
>Is there a way to keep accomplish this?
>
>It would be great if the RT31P2 had static DHCP - perhaps there's
>another way
>to accomplish the same function.
>
>Can I configure the DI-604 to have a static address and turn off
>DHCP/NAT on the
>RT31P2? A static WAN address on the DI-604 requires I define also DNS
>server addresses
>and I'd like to keep getting those automatically.
>
>Any other suggestions?
>
>Chris
>cjtwantstoknow

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558
Anonymous
August 25, 2005 2:36:41 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

Jeff,

Thanks for your advice!

I use the DI-604 because it gives me the ability to assign an IP
address to a MAC address in the static dhcp setup. Since I share the
wireless network with others, it allows me to assign specific IP
addresses that in turn can be specified in the firewalls on my PCs.
This keeps my neighbors out of my PCs and me out of theirs.
I like to keep the desktop and the wireless clients on the same
network/router because then I don't have to deal with port-forwarding
to support Microsoft file sharing.

The RT31P2 doesn't support static dhcp so that's why I don't use it
instead of the DI-604. As far as the wireless device goes, it's there
because it is physically situated away from everything else and using
its LAN ports is not possible. The desktop needs to be wired because
certain applications require a network card and don't work with
wireless cards.

I'll probably end up plugging the desktop (the FTP server) into the
RT31P2 and assign it a fixed IP address.

BTW - The wireless device is a Parkervision WR1500.

Chris

cjtwantstoknow
Related resources
Anonymous
August 25, 2005 3:51:46 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

On 25 Aug 2005 10:36:41 -0700, cjtwantstoknow@yahoo.com wrote:

>I use the DI-604 because it gives me the ability to assign an IP
>address to a MAC address in the static dhcp setup. Since I share the
>wireless network with others, it allows me to assign specific IP
>addresses that in turn can be specified in the firewalls on my PCs.

Well, I guess that's one way of doing it.

>This keeps my neighbors out of my PCs and me out of theirs.
>I like to keep the desktop and the wireless clients on the same
>network/router because then I don't have to deal with port-forwarding
>to support Microsoft file sharing.
>
>The RT31P2 doesn't support static dhcp so that's why I don't use it
>instead of the DI-604. As far as the wireless device goes, it's there
>because it is physically situated away from everything else and using
>its LAN ports is not possible. The desktop needs to be wired because
>certain applications require a network card and don't work with
>wireless cards.
>
>I'll probably end up plugging the desktop (the FTP server) into the
>RT31P2 and assign it a fixed IP address.

Well, that will work, but if you want to preserve your existing setup
and make it easy to get to your desktop PC from other machines, all
you need to do is assign a static IP address to the DI-604 *WAN* port.
I think the RT31P2 is 192.168.15.1. Use something like:
IP 192.168.15.15
GW 192.168.15.1
NM 255.255.255.0
DNS 192.168.15.1
Then, port forward 20 and 21 (ftp) on the RT31P2 to 192.168.15.15 and
again in the DLink DI-604 to the IP address of the ftp server.

>BTW - The wireless device is a Parkervision WR1500.

Thanks.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
AE6KS 831-336-2558
Anonymous
August 25, 2005 6:44:51 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> It would be great if the RT31P2 had static DHCP - perhaps there's
> another way
> to accomplish the same function.

There's no such thing as static DHCP, you can create a reservation but
then there's no point using DHCP in that case for one machine.

Why not just leave the Dlink out completely, it serves no purpose and
just configure a DHCP scope for the required number of PC's and then
give the desktop a static IP address that does not exist in the DHCP
scope?

David.
Anonymous
August 25, 2005 6:44:52 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

yeah replace the 604 with a switch
"David Taylor" <djtaylor@bigfoot.com> wrote in message
news:MPG.1d77e8d05fef79d7989da2@news.cable.ntlworld.com...
>> It would be great if the RT31P2 had static DHCP - perhaps there's
>> another way
>> to accomplish the same function.
>
> There's no such thing as static DHCP, you can create a reservation but
> then there's no point using DHCP in that case for one machine.
>
> Why not just leave the Dlink out completely, it serves no purpose and
> just configure a DHCP scope for the required number of PC's and then
> give the desktop a static IP address that does not exist in the DHCP
> scope?
>
> David.
Anonymous
August 25, 2005 7:09:04 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

David Taylor <djtaylor@bigfoot.com> wrote:
>> It would be great if the RT31P2 had static DHCP - perhaps there's
>> another way
>> to accomplish the same function.
>
> There's no such thing as static DHCP, you can create a reservation but
> then there's no point using DHCP in that case for one machine.

You can absolutely use DHCP to manage static addresses.

> Why not just leave the Dlink out completely, it serves no purpose

Yeah, that was my question too.

miguel
--
Hit The Road! Photos from 36 countries on 5 continents: http://travel.u.nu
Latest photos: Queens Day in Amsterdam; the Grand Canyon; Amman, Jordan
Anonymous
August 25, 2005 7:11:09 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

<cjtwantstoknow@yahoo.com> wrote:
> I use the DI-604 because it gives me the ability to assign an IP
> address to a MAC address in the static dhcp setup. Since I share the
> wireless network with others, it allows me to assign specific IP
> addresses that in turn can be specified in the firewalls on my PCs.
> This keeps my neighbors out of my PCs and me out of theirs.

Only if they're cooperative. It's easy enough for them to clone a MAC once a
"trusted" machine is turned off.

miguel
--
Hit The Road! Photos from 36 countries on 5 continents: http://travel.u.nu
Latest photos: Queens Day in Amsterdam; the Grand Canyon; Amman, Jordan
Anonymous
August 25, 2005 10:11:43 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> I use the DI-604 because it gives me the ability to assign an IP
> address to a MAC address in the static dhcp setup. Since I share the
> wireless network with others, it allows me to assign specific IP

Like several have said, there's no need to use DHCP and then defeat it
by reserving an address to a machine like you are doing. Just assign a
static IP address to the box but use one outside of the DHCP range.

> I like to keep the desktop and the wireless clients on the same
> network/router because then I don't have to deal with port-forwarding
> to support Microsoft file sharing.

That would still be the case.

> The RT31P2 doesn't support static dhcp so that's why I don't use it
> instead of the DI-604. As far as the wireless device goes, it's there

So configure a static IP address, job done.

> its LAN ports is not possible. The desktop needs to be wired because
> certain applications require a network card and don't work with
> wireless cards.

Jeff said use a switch, that'll work just fine.

> I'll probably end up plugging the desktop (the FTP server) into the
> RT31P2 and assign it a fixed IP address.

Best solution.
Anonymous
August 26, 2005 1:24:00 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> You can absolutely use DHCP to manage static addresses.

I am fully aware of reservations! My point here is that the definition
of DHCP is Dynamic and there's no such thing as Static Dynamic any more
than there's hot/cold or up/down at the same time it is not possible to
have opposites like this, a DHCP reservation is a DHCP reservation but
you cannot manage a clients static address, only hand out the same
dynamically assigned reserved address by a DHCPOffer upon the
DHCPRequest or DHCPRenew packets. Yes, i'm being picky! :) 

This is unfortunate blatant abuse of terminology, I'll blame Linksys and
Dlink for this at this time.

It's rather pointless setting up DHCP to manage one machine as a static
address, that's more work than is required.

David.
Anonymous
August 26, 2005 1:24:40 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> Only if they're cooperative. It's easy enough for them to clone a MAC once a
> "trusted" machine is turned off.

or change their IP addresses
Anonymous
August 26, 2005 7:16:23 AM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

Thanks Jeff!

I didn't realize that I can specify the router as the DNS server. I
guess the RT31P2 just forwards the request.

I assigned a static address to the DI-604 (outside dhcp range) and it
works as desired.

I realize that I have more devices than needed. Perhaps I'll eliminate
the DI-604 and assign my machines to fixed IP addresses instead.

Chris
Anonymous
August 26, 2005 2:38:28 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> I didn't realize that I can specify the router as the DNS server. I
> guess the RT31P2 just forwards the request.

Correct.

> I realize that I have more devices than needed. Perhaps I'll eliminate
> the DI-604 and assign my machines to fixed IP addresses instead.

Sell the DI-604 on ebay ;) 
Anonymous
August 26, 2005 2:38:29 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

David Taylor wrote:
>
>> I realize that I have more devices than needed. Perhaps I'll eliminate
>> the DI-604 and assign my machines to fixed IP addresses instead.
>
> Sell the DI-604 on ebay ;) 

Can you get enough to make it worthwhile? They're pretty cheap.
--
derek
Anonymous
August 26, 2005 5:39:24 PM

Archived from groups: comp.dcom.voice-over-ip,comp.dcom.net-management,alt.internet.wireless (More info?)

> Can you get enough to make it worthwhile? They're pretty cheap.

They are cheap but it's redundant right now so might as well make a few
pennies. :) 
!