I was called in to rectify a networking problem for a customer. I did so, 
but I'd be interested to know if there is any other way in which it could 
have been fixed.

The setup (when I was called in) was as follows:

- BT HomeHub router connected to ADSL and connected wirelessly to an XP PC; 
router and PC were in different rooms
- a second BT HomeHub connected by Ethernet to the PC and also by Ethernet 
to a printer; this router had no ADSL connection and was presumably being 
used purely for its hub
- both the wireless and Ethernet ports of the PC had IP addresses in the 
same subnet: the wireless one was set by DHCP from the first HomeHub; the 
Ethernet one was set statically at the PC.
- both routers had the same IP address, so the gateway address that the ADSL 
router handed out was the same as the address of the second router.
- a printer driver was configured to print to a TCP port (specified by IP 
address)
- the printer did not have a USB port, so the only way for the PC to 
communicate with it was by Ethernet

With the Ethernet cable plugged in, the PC (not surprisingly) was unable to 
access the internet - presumably because it had two network ports with 
addresses in the same subnet, one of which had access to the internet and 
the other which didn't. Therefore it was undefined which port the PC's TCP 
would try to use to access the internet. Also the PC might try to use the 
non-ADSL router as the gateway (remember both routers had the same address!)

The customer had got into the habit of unplugging the Ethernet cable when he 
wanted to access the internet and plugging in the cable when he wanted to 
print. This was not exactly a good way of working and it was driving him 
mad.

Having mused about the parentage and competence of the guy that installed 
this intriguing setup (who was the support engineer who installed the 
printer), I resolved the problem by moving the ADSL-connected router so the 
printer and the PC could be both be plugged into it. The wireless adaptor in 
the PC and the second (non-ADSL-connected) router became obselete.

This now worked because the PC had a single means of accessing both the 
internet and the LAN-connected printer, rather than internet on one PC 
network port and printer on another.

The only downside was that the customer will need to install a phone 
extension to connect his router to ADSL - but he was planning to do that 
anyway.

So that solved the problem, but is there a better/different solution which 
would have worked without needing the phone line to be moved?

On Tue, 27 Jan 2009 01:32:22 -0000
"Mortimer"  wrote:

> So that solved the problem, but is there a better/different solution
> which would have worked without needing the phone line to be moved? 
> 
> 
Why not just plug the printer into the PC?

"Rob Morley"  wrote in message 
news:20090127061843.1be1c5e9@bluemoon...
> On Tue, 27 Jan 2009 01:32:22 -0000
> "Mortimer"  wrote:
>
>> So that solved the problem, but is there a better/different solution
>> which would have worked without needing the phone line to be moved?
>>
>>
> Why not just plug the printer into the PC?

Leaving aside the second (non-ADSL-connected) router acting as a hub to 
avoid using a crossover cable, that is how the configuration was when I was 
called in.

Remember that the printer *only* had a LAN connection and did not have a USB 
port.

Mortimer wrote:
> I was called in to rectify a networking problem for a customer. I did so, 
> but I'd be interested to know if there is any other way in which it could 
> have been fixed.
> 
> The setup (when I was called in) was as follows:
> 
> - BT HomeHub router connected to ADSL and connected wirelessly to an XP PC; 
> router and PC were in different rooms
> - a second BT HomeHub connected by Ethernet to the PC and also by Ethernet 
> to a printer; this router had no ADSL connection and was presumably being 
> used purely for its hub
> - both the wireless and Ethernet ports of the PC had IP addresses in the 
> same subnet: the wireless one was set by DHCP from the first HomeHub; the 
> Ethernet one was set statically at the PC.
> - both routers had the same IP address, so the gateway address that the ADSL 
> router handed out was the same as the address of the second router.
> - a printer driver was configured to print to a TCP port (specified by IP 
> address)
> - the printer did not have a USB port, so the only way for the PC to 
> communicate with it was by Ethernet
> 
> With the Ethernet cable plugged in, the PC (not surprisingly) was unable to 
> access the internet - presumably because it had two network ports with 
> addresses in the same subnet, one of which had access to the internet and 
> the other which didn't. Therefore it was undefined which port the PC's TCP 
> would try to use to access the internet. Also the PC might try to use the 
> non-ADSL router as the gateway (remember both routers had the same address!)
> 
> The customer had got into the habit of unplugging the Ethernet cable when he 
> wanted to access the internet and plugging in the cable when he wanted to 
> print. This was not exactly a good way of working and it was driving him 
> mad.
> 
> Having mused about the parentage and competence of the guy that installed 
> this intriguing setup (who was the support engineer who installed the 
> printer), I resolved the problem by moving the ADSL-connected router so the 
> printer and the PC could be both be plugged into it. The wireless adaptor in 
> the PC and the second (non-ADSL-connected) router became obselete.
> 
> This now worked because the PC had a single means of accessing both the 
> internet and the LAN-connected printer, rather than internet on one PC 
> network port and printer on another.
> 
> The only downside was that the customer will need to install a phone 
> extension to connect his router to ADSL - but he was planning to do that 
> anyway.
> 
> So that solved the problem, but is there a better/different solution which 
> would have worked without needing the phone line to be moved? 
> 
> 

1. change the PC ethernet IP address and the printer IP address to
another subnet (the router is not used, so doesn't need to change and
the in-built switch will handle multiple subnets anyway).

2. change the second router to a different sub net and use DHCP without
a gateway address.

3. changing the routing in XP might work, but with the same subnet, you
would expect problems.

-- 
PeeGee

"Nothing should be able to load itself onto a computer without the
knowledge or consent of the computer user. Software should also be able
to be removed from a computer easily."
Peter Cullen, Microsoft Chief Privacy Strategist (Computing 18 Aug 05)

On Tue, 27 Jan 2009 08:03:07 -0000
"Mortimer"  wrote:

> "Rob Morley"  wrote in message 
> news:20090127061843.1be1c5e9@bluemoon...
> > On Tue, 27 Jan 2009 01:32:22 -0000
> > "Mortimer"  wrote:
> >
> >> So that solved the problem, but is there a better/different
> >> solution which would have worked without needing the phone line to
> >> be moved?
> >>
> >>
> > Why not just plug the printer into the PC?
> 
> Leaving aside the second (non-ADSL-connected) router acting as a hub
> to avoid using a crossover cable, that is how the configuration was
> when I was called in.

Unless the LAN card is ancient it will probably have auto MDI/MDI-X, so
no need for a crossover cable.  Even if it doesn't, using a crossover
cable is way neater than using a router as a hub just to use
straight-through cables.
> 
> Remember that the printer *only* had a LAN connection and did not
> have a USB port. 
> 
And the PC has an ethernet port ...

"PeeGee"  wrote in message 
news:glml9o$pqc$1@news.motzarella.org...
> 1. change the PC ethernet IP address and the printer IP address to
> another subnet (the router is not used, so doesn't need to change and
> the in-built switch will handle multiple subnets anyway).
>
> 2. change the second router to a different sub net and use DHCP without
> a gateway address.

I wondered about putting the PC's Ethernet port and printer on a different 
subnet to the real router's subnet as used by the wireless port. Would I 
also have to change the second router's own IP address (probably to an 
address in the same subnet as the devices that are connected to it) so that 
when the PC tried to access the gateway address that the real router quoted, 
only one router would reply?

"Rob Morley"  wrote in message 
news:20090127110816.06e3fd33@bluemoon...
> On Tue, 27 Jan 2009 08:03:07 -0000
> "Mortimer"  wrote:
>
>> "Rob Morley"  wrote in message
>> news:20090127061843.1be1c5e9@bluemoon...
>> > On Tue, 27 Jan 2009 01:32:22 -0000
>> > "Mortimer"  wrote:
>> >
>> >> So that solved the problem, but is there a better/different
>> >> solution which would have worked without needing the phone line to
>> >> be moved?
>> >>
>> >>
>> > Why not just plug the printer into the PC?
>>
>> Leaving aside the second (non-ADSL-connected) router acting as a hub
>> to avoid using a crossover cable, that is how the configuration was
>> when I was called in.
>
> Unless the LAN card is ancient it will probably have auto MDI/MDI-X, so
> no need for a crossover cable.  Even if it doesn't, using a crossover
> cable is way neater than using a router as a hub just to use
> straight-through cables.
>>
>> Remember that the printer *only* had a LAN connection and did not
>> have a USB port.
>>
> And the PC has an ethernet port ...

Yes, what I was meaning was: you were suggesting something that was the same 
as the original setup, with the exception of replacing the router by 
straight-through or crossover cable, and I wasn't sure how this would help 
the problem. I know that many modern Ethernet cards are auto-sensing (though 
I have seen a few exceptions!) and that a router is overkill in this case 
unless it is being used for its DHCP server.

Mortimer  wrote:
> The only downside was that the customer will need to install a phone
> extension to connect his router to ADSL - but he was planning to do
> that anyway.

> So that solved the problem, but is there a better/different solution
> which would have worked without needing the phone line to be moved?

Assuming a single PC. Put ADSL router and PC (wireless) on the same
network; PC with DHCP address if you like. Create a separate subnet for
the PC's NIC and printer, connected with a crossover cable.

	ADSL Router 192.168.0.254/24
	PC (wireless, DHCP) 192.168.0.*/24; gateway & DNS @ 192.168.0.254

	PC (wired) 192.168.1.1/24
	Printer (wired) 192.168.1.241/24

These last-octet values are my preference - it doesn't really matter if
they get swapped around as long as the intent remains the same.

But since your customer has decided they need to install a phone extension
anyway it seems to me that you could more simply just put everything
onto the same subnet and reduce the complexity.

Chris

Mortimer writes:

> [blah blah two DSL routers being used blah blah]

A PC can have two network interfaces on the same subnet - it's not a
problem unless they have the same IP, and as long as they are never
bridged. The only thing you might see on some OSes is event log messages
saying that an ARP reply was received on an interface different to the
one it was transmitted on.

The easy solution would be to just make sure both DSL routers have a
different LAN IP (IP address conflicts are bad, mmkay), and disabling
DHCP on the non-DSL-connected non-routing-router.

The bit in your post which completely baffled me is...
"- both routers had the same IP address, so the gateway address that the
ADSL router handed out was the same as the address of the second
router." - both had the same IP, but the gateway IP handed out by
[whichever device sent out DHCP replies first?] *specifically* belonged
to the second router?? Eh?

Unless I misread your post, there's really no reason for anything to be
on a different subnet. The only thing to make sure you avoid is a
routing loop, easily identified by all the flickering LEDs.

In addition, from a DSL stability standpoint it's best to have the
router as close to the master socket as possible, with as little
extension cabling as possible anywhere else.

Also: post hoc ergo propter hoc.

E&OE

Mortimer wrote:
> "PeeGee"  wrote in message 
> news:glml9o$pqc$1@news.motzarella.org...
>> 1. change the PC ethernet IP address and the printer IP address to
>> another subnet (the router is not used, so doesn't need to change and
>> the in-built switch will handle multiple subnets anyway).
>>
>> 2. change the second router to a different sub net and use DHCP without
>> a gateway address.
> 
> I wondered about putting the PC's Ethernet port and printer on a different 
> subnet to the real router's subnet as used by the wireless port. Would I 
> also have to change the second router's own IP address (probably to an 
> address in the same subnet as the devices that are connected to it) so that 
> when the PC tried to access the gateway address that the real router quoted, 
> only one router would reply? 
> 
> 

If you change the subnet for the PC/printer network, the second router
address doesn't matter, but changing it as well will give added "peace
of mind" and allow you to access it from the PC (if it's on a different
subnet address, it won't be (easily) accessible) :-) It will also allow
you to use DHCP (with no gateway entry) if you wish to at any time.

-- 
PeeGee

"Nothing should be able to load itself onto a computer without the
knowledge or consent of the computer user. Software should also be able
to be removed from a computer easily."
Peter Cullen, Microsoft Chief Privacy Strategist (Computing 18 Aug 05)

"Mortimer"  wrote in message 
news:0LGdnaJXye-t-ePUnZ2dnUVZ8rOdnZ2d@posted.plusnet...
>I was called in to rectify a networking problem for a customer. I did so, 
>but I'd be interested to know if there is any other way in which it could 
>have been fixed.
>
> The only downside was that the customer will need to install a phone 
> extension to connect his router to ADSL - but he was planning to do that 
> anyway.
>
> So that solved the problem, but is there a better/different solution which 
> would have worked without needing the phone line to be moved?
>
So you didn't fix it as he wanted, you caused additional expense by taking 
the
easy way out.
Next time get someone who knows what they are doing.  What's the name of
your company so people can avoid you!

"Mortimer"  wrote in message 
news:f9OdnWnNPMcDcePUnZ2dnUVZ8sXinZ2d@posted.plusnet...
> "PeeGee"  wrote in message 
> news:glml9o$pqc$1@news.motzarella.org...
>> 1. change the PC ethernet IP address and the printer IP address to
>> another subnet (the router is not used, so doesn't need to change and
>> the in-built switch will handle multiple subnets anyway).
>>
>> 2. change the second router to a different sub net and use DHCP without
>> a gateway address.
>
> I wondered about putting the PC's Ethernet port and printer on a different 
> subnet to the real router's subnet as used by the wireless port. Would I 
> also have to change the second router's own IP address (probably to an 
> address in the same subnet as the devices that are connected to it) so 
> that when the PC tried to access the gateway address that the real router 
> quoted, only one router would reply?
>
>
So you HAVE NOT solved the problem! You have probably charged
a "customer" to do something and want the answer from people that
know a bit more about computers to pass it off as your own work.
Terrible!
I hate cowboys and you're making yourself sound like one.

On Tue, 27 Jan 2009 12:27:38 -0000
"Mortimer"  wrote:

> Yes, what I was meaning was: you were suggesting something that was
> the same as the original setup, with the exception of replacing the
> router by straight-through or crossover cable, and I wasn't sure how
> this would help the problem.

You said both routers were using the same IP address - remove one
(that's not needed anyway) and you fix that.  Then just set the printer
to use a different network and configure the ethernet NIC appropriately.