Connecting a router question.

Can I connect a Modem/router to a wireless router (Linksys WRT54G)? I am
finding it hard to get hold of a stand alone ADSL modem with an ethernet
port.

Russ

On Fri, 1 Oct 2004 18:11:46 +0000 (UTC), "Mooncat" <(E-Mail Removed)>
wrote:

>Can I connect a Modem/router to a wireless router (Linksys WRT54G)? I am
>finding it hard to get hold of a stand alone ADSL modem with an ethernet
>port.
Never in this world there are plenty of them about Dynamode,Thompson
Speed touch to name two and there are lots more besides which I cannot
bring to mind at the moment . I am using a Speed touch internal
selling for just over eight quid at Scan Computers and it is perfect
the external is about £ 30.00 .

"Mooncat" <(E-Mail Removed)> wrote in message news:<cjk6l2$n5b$(E-Mail Removed)>...
> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?

Yes, but this is really a bit of a kludge. Any machines connected to
the wired ports of the modem-router will be on a different subnet from
wirelessly-connected machines, and will be unable to file- &
print-share with them.

> I am
> finding it hard to get hold of a stand alone ADSL modem with an ethernet
> port.

<http://www.broadbandbuyer.co.uk/Shop/ShopSearch.asp?CategoryID=34>

You really don't want to go this route.

Unless you're doing something clever like installing a different
version of Linux on the Linksys, get an all-in-one wireless ADSL
modem-router & flog the Linksys on fleeBay. There's a lot of
competition amongst manufactures of wireless ADSL routers at the
moment, and your Linksys will appeal to the "bargain hunters" on eBay.

Get one of these instead:
<http://www.broadbandbuyer.co.uk/Shop/ShopDetail.asp?ProductID=1094>
The PCMCIA card is free, or practically so, at the moment, and if you
don't want or need it you can always sell that on, too, to further
offset the costs. I wouldn't be surprised if this turned out cheaper
than your initial suggestions, and MUCH neater.

Stroller.

On 01 Oct 2004 in uk.telecom.broadband, (E-Mail Removed) wrote:

>On Fri, 1 Oct 2004 "Mooncat" <(E-Mail Removed)> wrote:
>>hard to get hold of a stand alone ADSL modem with an ethernet port.

The D-Link DSL 300T ethernet modem possibly fits the bill...

>Never in this world there are plenty of them about ...
>I am using a Speed touch internal ...

Does your Speedtouch internal have an ethernet port (needed by Mooncat) ?

In MsgID<(E-Mail Removed) > within
uk.telecom.broadband, 'Stroller' wrote:

>"Mooncat" <(E-Mail Removed)> wrote in message news:<cjk6l2$n5b$(E-Mail Removed)>...
>> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?
>
>Yes, but this is really a bit of a kludge.


>Any machines connected to
>the wired ports of the modem-router will be on a different subnet from
>wirelessly-connected machines, and will be unable to file- &
>print-share with them.

I thought that was the whole purpose of a router?
To relay packets between (sub)networks?


--
Dave Johnson - (E-Mail Removed)

On 1 Oct 2004 18:25:09 -0700, (E-Mail Removed) (Stroller) wrote:

>"Mooncat" <(E-Mail Removed)> wrote in message news:<cjk6l2$n5b$(E-Mail Removed)>...
>> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?
>
>Yes, but this is really a bit of a kludge. Any machines connected to
>the wired ports of the modem-router will be on a different subnet from
>wirelessly-connected machines, and will be unable to file- &
>print-share with them.
>

Why?

Surely that will only be true if you set it up that way. There is no
reason why they have to be set up to use different subnets.



>> I am
>> finding it hard to get hold of a stand alone ADSL modem with an ethernet
>> port.
>
><http://www.broadbandbuyer.co.uk/Shop/ShopSearch.asp?CategoryID=34>
>
>You really don't want to go this route.

Why not?

If he was starting from scratch, I'd agree.

But from where he is, that saves him roughly 50%, although as you say,
that could be offset by selling his existing router.

But on the other hand, he already has things set up to work with his
existing router, and adding the modem would be trivial, for the sake
of one extra box, cable, and power lead.


--
Alex Heney, Global Villager
The brain you have reached is out of order at this time.

To reply by email, my address is alexATheneyDOTplusDOTcom

Dave J <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>. ..
> In MsgID<(E-Mail Removed) > within
> uk.telecom.broadband, 'Stroller' wrote:
>
> >"Mooncat" <(E-Mail Removed)> wrote in message news:<cjk6l2$n5b$(E-Mail Removed)>...
> >> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?
> >
>
> >Any machines connected to
> >the wired ports of the modem-router will be on a different subnet from
> >wirelessly-connected machines, and will be unable to file- &
> >print-share with them.
>
> I thought that was the whole purpose of a router?
> To relay packets between (sub)networks?

Yes, but domestic routers typically do only one-way NAT t private
address space. Thus they allow packets from machines behind the router
to get out, and to receive replies, but drop all unsolicited requests
from outside the NAT.

However, as Mr Heney observes, the OP could most likely configure the
Linksys as a bridge, and avoid this problem. I don't know what I was
thinking, that I forgot this & apologise for the confusion.

Stroller.

In MsgID<(E-Mail Removed) m> within
uk.telecom.broadband, 'Stroller' wrote:

>Dave J <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>. ..
>> In MsgID<(E-Mail Removed) > within
>> uk.telecom.broadband, 'Stroller' wrote:
>>
>> >"Mooncat" <(E-Mail Removed)> wrote in message news:<cjk6l2$n5b$(E-Mail Removed)>...
>> >> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?
>> >
>>
>> >Any machines connected to
>> >the wired ports of the modem-router will be on a different subnet from
>> >wirelessly-connected machines, and will be unable to file- &
>> >print-share with them.
>>
>> I thought that was the whole purpose of a router?
>> To relay packets between (sub)networks?
>
>Yes, but domestic routers typically do only one-way NAT t private
>address space. Thus they allow packets from machines behind the router
>to get out, and to receive replies, but drop all unsolicited requests
>from outside the NAT.

Drop all unsolicited requests from outside the NATed IP block?

Sorry for silly questions, I'm still learning.

I'm still not quite sure on your meanings.

From where I'm sitting, it looks like the problem is one or more of
these things,

a) the modem router won't route (at all) between its wired ports[1].

b) you cannot set a subnet on the modem-router's wired port's IPs.
- So you couldn't connect a port to (say) a hub.

c) you cannot change the wireless router's subnet to match the
modem-router's.

d) The wireless router expects to NAT everything on the way out of a
special wired 'modem' port.

[1] If this is the case then IMHO it is not a router. Multi port modem
would be a better descriptor.

Thanks if you (or anyone else) explains. I am reasonably knowledgable
about 'real' routers/switches/networks but these toy things are liable
to flumox me into wasting some money if I don't suss them out first.

--
Dave Johnson - (E-Mail Removed)

In message <(E-Mail Removed)>, Dave J
<(E-Mail Removed)> writes
>In MsgID<(E-Mail Removed) m> within
>uk.telecom.broadband, 'Stroller' wrote:
>
>>Dave J <(E-Mail Removed)> wrote in message
>>news:<(E-Mail Removed) >...
>>> In MsgID<(E-Mail Removed) > within
>>> uk.telecom.broadband, 'Stroller' wrote:
>>>
>>> >"Mooncat" <(E-Mail Removed)> wrote in message
>>> >news:<cjk6l2$n5b$(E-Mail Removed)>...
>>> >> Can I connect a Modem/router to a wireless router (Linksys WRT54G)?
>>> >
>>>
>>> >Any machines connected to
>>> >the wired ports of the modem-router will be on a different subnet from
>>> >wirelessly-connected machines, and will be unable to file- &
>>> >print-share with them.
>>>
>>> I thought that was the whole purpose of a router?
>>> To relay packets between (sub)networks?

There's some crossed purposes going on here.

What is being talked here about is the one way I wouldn't connect the
two boxes together - connect the wired network devices to the ADSL
router and connect the WAN port of the wireless Ethernet router to the
ADSL router. That leaves the devices on the wireless double NATted and
on a different subnet to those wired devices.


Either connect one of the LAN ports of the wireless router to the ADSL
router and use it just as a wireless base station, or use the ADSL
router either in something like a half-bridge configuration (if you have
a single IP address) or no-NAT mode (if you have a routed IP block) and
connect everything to the wireless router.


>>Yes, but domestic routers typically do only one-way NAT t private
>>address space. Thus they allow packets from machines behind the router
>>to get out, and to receive replies, but drop all unsolicited requests
>>from outside the NAT.
>
>Drop all unsolicited requests from outside the NATed IP block?
>
>Sorry for silly questions, I'm still learning.

It wasn't put very well IMHO - does it make sense now?


>I'm still not quite sure on your meanings.
>
>From where I'm sitting, it looks like the problem is one or more of
>these things,
>
>a) the modem router won't route (at all) between its wired ports[1].
>
>b) you cannot set a subnet on the modem-router's wired port's IPs.
> - So you couldn't connect a port to (say) a hub.
>
>c) you cannot change the wireless router's subnet to match the
> modem-router's.
>
>d) The wireless router expects to NAT everything on the way out of a
> special wired 'modem' port.
>
>[1] If this is the case then IMHO it is not a router. Multi port modem
>would be a better descriptor.
>
>Thanks if you (or anyone else) explains. I am reasonably knowledgable
>about 'real' routers/switches/networks but these toy things are liable
>to flumox me into wasting some money if I don't suss them out first.

I've got a couple of bits of kit in the rack behind me one of which
doesn't really qualify for the toy description - but here's an example.


The ADSL router is a cheap ZyXEL Prestige 650H-E1 - there's no point
spending a lot of money on a decent ADSL router for my application.

I have a /29 with Zen - call it a.b.c.88 / 29 for argument.

Zen use the highest usable IP address for the router - so, in my case,
that's a.b.c.94 (a.b.c.95 is the broadcast address).


The Prestige is configured to have a LAN IP address of a.b.c.94, subnet
mask 255.255.255.248, and NAT is off, as is the firewall (no sensible
way of configuring it).

The Prestige is connected to the WAN 1 port of a ZyXEL ZyWALL 35, which
is a fairly decent multi-NAT router, firewall, bandwidth management,
dial backup (with a modem) and IPsec box, which supports multiple LAN
and DMZ subnets (two separate broadcast domains and sets of firewall
rules).


In fact, to make my life easier, the Prestige and ZyWALL are not
directly connected together - the connection goes through my managed
switch on a separate VLAN to the LAN, so that I can get at it from my
main workstation which supports tagged operation on multiple VLANs.

If you don't want the dual WAN features of the ZyWALL 35 and can get
away with fewer IPsec tunnels, the ZyWALL 5 is available for a little
over 200 pounds plus VAT - and IMHO is rather more powerful than even
the most expensive ADSL router (Cisco aside, most likely).

The Prestige 650H-E1 is only 35 pounds from broadbandbuyer.co.uk -
though it is capable of multi-NAT operation with a fairly decent
firewall just by itself; it also has a four port switch built in.


The ZyWALL is set up with an IP address of a.b.c.93, subnet mask
255.255.255.248, gateway address a.b.c.94 - and runs multi-NAT on the
other addresses in the block, also its firewall is on.



For single IP address accounts, this approach doesn't work. The easiest
thing to do is to buy a router with all the facilities you need built in
including the ADSL modem.

The alternative is to use a device that will pass through the IP
address. The PPP Half Bridge mode of Conexant based gear will do this
(though with the penalty of a very short DHCP lease) - Westell routers
have various techniques you can use (look up "Single Static IP" in the
Westell 6100 manual available from www.westell.com).

Ignore American references to PPPoE operation, where you can run the
ADSL kit as a bridge and terminate the PPPoE session on another piece of
equipment. PPPoA (as I think all UK ADSL ISPs use, with the exception of
some AOL connections) has to terminate on the DSL kit.


The manuals for all the ZyXEL kit can be got in PDF format from
ftp://ftp.zyxel.com




David
--
David Wood
(E-Mail Removed)

In MsgID<(E-Mail Removed)> within uk.telecom.broadband,
'David Wood' wrote:

[..]

>>>> I thought that was the whole purpose of a router?
>>>> To relay packets between (sub)networks?
>
>There's some crossed purposes going on here.

Yes, thank you for the further explanation, though I'm probably still
as confused.

I've taken my time replying as you set me looking things up, and
grepping some new stuff along with some of the things I'd already
heard about. Doesn't mean I've anything like got it right of course,
but you've helped a bit in provoking the reading.

>
>What is being talked here about is the one way I wouldn't connect the
>two boxes together - connect the wired network devices to the ADSL
>router and connect the WAN port of the wireless Ethernet router to the
>ADSL router. That leaves the devices on the wireless double NATted and
>on a different subnet to those wired devices.

The way I'd have *expected* it to work would have been for the
wireless router to route between the wireless devices, with the ADSL
router as its default route, and for the ADSL router to have NAT set
up only on its outgoing port, with that as /its/ default route, plus
routes for the wireless subnets. Hopefully it would then route between
the wireless devices and the wired ones with no need for NAT except
for unknown (external) destinations.

This leads me to think I still don't really understand the problem.

>Either connect one of the LAN ports of the wireless router to the ADSL
>router and use it just as a wireless base station,

>or use the ADSL
>router either in something like a half-bridge configuration (if you have
>a single IP address) or no-NAT mode (if you have a routed IP block) and
>connect everything to the wireless router.

[..]

>>Sorry for silly questions, I'm still learning.
>
>It wasn't put very well IMHO - does it make sense now?

More than it did, my fault for dropping in to the middle of a
discussion I think.

[..]

>The Prestige is configured to have a LAN IP address of a.b.c.94, subnet
>mask 255.255.255.248, and NAT is off, as is the firewall (no sensible
>way of configuring it).

So, it won't route at the same time as doing NAT only on the one
outgoing interface then?

This is horrible, I'm realising just how little I know..
BTW, that's in spite of getting constant middle 90s in the subtests
and EOS exams up to 3/4 of the way through a CCNA course (ie now)

>
>The Prestige is connected to the WAN 1 port of a ZyXEL ZyWALL 35, which
>is a fairly decent multi-NAT router, firewall, bandwidth management,
>dial backup (with a modem) and IPsec box, which supports multiple LAN
>and DMZ subnets (two separate broadcast domains and sets of firewall
>rules).

Fair enough, by my standards that is *not* a toy..

[..]
>
>If you don't want the dual WAN features of the ZyWALL 35 and can get
>away with fewer IPsec tunnels, the ZyWALL 5 is available for a little
>over 200 pounds plus VAT - and IMHO is rather more powerful than even
>the most expensive ADSL router (Cisco aside, most likely).

Sounds a good recomendation to me, esp as it's happy with VPN.

>
>The Prestige 650H-E1 is only 35 pounds from broadbandbuyer.co.uk -
>though it is capable of multi-NAT operation with a fairly decent
>firewall just by itself; it also has a four port switch built in.
>
>
>The ZyWALL is set up with an IP address of a.b.c.93, subnet mask
>255.255.255.248, gateway address a.b.c.94 - and runs multi-NAT on the
>other addresses in the block, also its firewall is on.

Ah, multi-nat means nat to/from several subnetworks? Perhaps even
to/from several external IPs?

>For single IP address accounts, this approach doesn't work. The easiest
>thing to do is to buy a router with all the facilities you need built in
>including the ADSL modem.
>
>The alternative is to use a device that will pass through the IP
>address.

Setting routers to bridge mode is something we've only glanced upon so
far, it seems to mean pretty much what it says, as in behave like a
switch and blindly relay packets. Only kink being that I didn't know
until reading up now about it handling the PPP. That (I should think)
makes it rather useful.

>The PPP Half Bridge mode of Conexant based gear will do this
>(though with the penalty of a very short DHCP lease) - Westell routers
>have various techniques you can use (look up "Single Static IP" in the
>Westell 6100 manual available from www.westell.com).

Haven't visited yet, just had a first look, seems like another reading
session.

>
>Ignore American references to PPPoE operation, where you can run the
>ADSL kit as a bridge and terminate the PPPoE session on another piece of
>equipment.

>PPPoA (as I think all UK ADSL ISPs use, with the exception of
>some AOL connections) has to terminate on the DSL kit.

<puzzled>

AFAICT PPP of all versions is just a sequence of bytes, why can't
PPPoA be relayed to a host which then deals with the LCP/NCP stuff?
(Not that I can see much reason for wanting to, mind you)

Thanks, and sorry for trying to use you as a teacher..

Dave J.
--
Dave Johnson - (E-Mail Removed)