modem/router gateway setting

modem/router gateway setting

Post by Andrew Wic » Thu, 13 Apr 2006 17:50:23

Setting up broadband last night, I was somewhat perplexed to find that
the gateway address on the RiscPC (OS4.02, EtherH16) had to be set to
the modem/router's LAN address (as per pv's guide), while on a WinXP
laptop (IBM T40) it had to be set (and later DCHP'd itself once I'd
worked out what was needed using static addresses) to the
modem/router's WAN address. Until XP was set to the WAN gateway, I
couldn't even ping the modem/router's LAN address (and yes, the subnet
mask was correct!-).

Just curious if there's a sensible explanation for the difference.

Am also finding the RiscPC keeps dropping the connection. I'll be
installing Adjust this weekend, so hopefully that will improve things
(a chance to reseat all the add-ons, if nothing else!).


modem/router gateway setting

Post by Alan Adam » Thu, 13 Apr 2006 18:55:19

In message < XXXX@XXXXX.COM >

As always the first thing to look at on XP is the firewall, although
it only blocks incoming activity, so I can't see how it would affect

This is a curious setup - you have an XP box whose IP address is set
to the LAN, but the default gateway is set to an address in a
different network. That shouldn't work! The reason is that in order to
access the default router it has to know how to send a packet to it,
and it can only send to its own LAN network. To send to anything else
it sends to the default router.

So to send to the default router, it first has to send to the default
router, to do which it has to send to the default router, etc...

Can you post the output of ipconfig /all at the command prompt of the
XP box?

The connection to the internet is maintained by the router. This
suggests that the RPC has a problem accessing systems on the LAN. Can
you confirm that by pinging the router and the XP box.

ping on the RPC will send pings continuously, for testing. Using -s
1024 as well will send large packets, which are good for stressing a


ping -s 1024 <address>

To do the same on the XP box use

ping -t -s 1024 <address>

Alan Adams, from Northamptonshire


modem/router gateway setting

Post by Andrew Wic » Thu, 13 Apr 2006 21:30:26

Thanks for the suggestions, which I'll try when I get home (posting
this from work!).

I did not have the XP box and RiscPC online at the same time (just a
crossover cable [1]from router to one or the other), but I have a hub I
can add to the mix and try LAN-side pinging.

[1] at least, it should be a crossover as that's what the manual says
you need for direct connection, but the wiring looks "straight" and
what I thought was a crossover cable doesn't work. More reasons to use
the hub!


modem/router gateway setting

Post by druc » Fri, 14 Apr 2006 02:23:10

That certainly isn't how its supposed to be done. The gateway must be an
address on the local network, so the machine knows how to route to other
networks - as the RPC is setup. You never normally use the WAN address when
using a router.

Well what do Microsoft know about networking. I suuggest if you want to
investigate, try an ms group and see what they have to say for themselves.


The ARM Club Free Software -
The 32bit Conversions Page -

modem/router gateway setting

Post by Andrew Wic » Fri, 14 Apr 2006 03:15:53

In a physical sense [1] it is on the local network - the router is a
little grey box on one end of a cable, the PC on the other, you can't
get much more local than that. Yet it failed to ping the "local"
address of the little grey box until I'd told it the public address of
said box. So I was perplexed.
Perplexed, yes. Bothered enough to investigate XP rather than sort out
the RPC's connection-dropping? Hardly!

[1] which I appreciate is not necessarily the sense that matters!


modem/router gateway setting

Post by Alan Adam » Fri, 14 Apr 2006 06:09:01

n message < XXXX@XXXXX.COM >
"Andrew Wickham" < XXXX@XXXXX.COM > wrote:

Your mention earlier of a cross-over cable bothers me a little. I
wonder whether there is some confusion over exactly what hardware is
in use.

A crossover cable is normally only required when connecting two of the
same type of equipment, i.e. two PCs or two hubs. (Most hubs
autosense, so you don't actually need a crossover cable here either.)

There are two types of box used for Broadband, usually called Moden
or Router.

The modem is the bit that connects to the WAN (telephone line) and
handles all the analog stuff. Cheap/simple connections often supply a
modem which typically has a USB connection, and might with luck also
have an Etnernet connection. The connected PC (only one at a time)
handles the logging in etc, so you will see this configuration being
done on the PC.

A broadband router is actually a modem combined with a router, and
often also a switch. The modem connects to the analog bits. The router
connects to the modem and handles logging in to your ISP's network.
The switch if present connects to the router and provides multiple
ports instead of just the one. Here you set up your account details on
the modem/router/switch box.

I *think* from earlier discussion that you have a router. The normal
configuration, for each PC (where the term PC includes RPC etc) is
that the PC has the same netmask as the router. It has a similar IP
address (differing only in the part of the address where the netmask
is 0). It has the router's IP address as both default gateway
(required) and Name Server (DNS server). The name server can
alternatively be set to go directly to the ISP's servers, if they will
tell you the address of those.

Now if your XP box can, and requires to, have the router's WAN address
as its default gateway, it suggests one of the following:

a: You have a modem, not a router
b: You have set up the IP addrsss of the PC in the WAN network of the
router, not the LAN network. (Hence the request for the output of
ipconfig /all)
c: The router has its LAN and WAN addreses in the same network

In all of these cases advice for fixing the RPC intermittent
connection will depend on how the PC is connected - not because the PC
is causing the problem, but it tells us more about your setup. The PC
symptoms point to a serious problem. The RPC problems may well be
linked to the same problem.

Things that might be wrong could include having the same IP address on
the RPC and the router, having an address which differs in the network
part as well as the host part (where the netmask is non-zero), having
the Name Servers set up incorrectly, in which case addresses will
work, names probably will not.

You said you will be getting Adjust. With that installed you can set
up DHCP, which means you will get the settings your router thinks are
right. Whether they are right will then depend on whether the router
is setup correctly.

Using DHCP be very careful of your hosts file - if possible it should
be empty, as the name-to-address mapping it represents can, and
probably will, change over time. Whether you can get things working
without a hosts file depends on whether the router's DHCP is correctly
linked to its DNS, and whether the sharing software you use can use
Windows name resolution. If not, then you will likely find you can
browse ex

modem/router gateway setting

Post by Andrew Wic » Fri, 14 Apr 2006 17:13:53

Alan Adams wrote:

Thanks for the continued interest. The WAN/LAN gateway oddity has gone
away, and the remaining problem may just be a RiscPC at the limits -
SA233, 258MB RAM+VRAM, SCSI podule, 486/100 PCCard, Etherlan600 NIC.
I'll be taking it to bits completely to fit Adjust ROMs, so will see
how it goes after a part-rebuild.
The manual says use a straight cable when linking the modem/router to a
hub and a crossover when linking to a single PC. On Tuesday I was
doing the latter, yesterday I tried the former.

My hub has a switch on one of the eight RJ45 sockets. Until the switch
is in the right place depending on the type of cable, the the light on
that line stays off.

Mine calls itself a modem/router. The config software includes routing
[snip re modem]

Indeed - with one USB and one RJ45 socket. I think you can use both
simultaneously, which IIUYC means there is a switch in there as well as
a modem and router!

The XP last night behaved as you would expect (ignoring my earlier
post), giving itself a 192.168.1.x address and using as the
gateway and DNS addresses. I could reach the internet but "ping" failed - but I think this may be due to the firewall, as
you suggested yesterday.
[snip re local addresses - I'm sure these are OK]

Ah - I'm using the ISP's DNS IPs in the RPC (as per Paul Vigay's
instructions), but the PC sets itself to use the modem/router's LAN
address as the primary DNS (and has no secondary). As you note above,
either (or all?) should work - I'll try the router as primary and the
ISP addresses as secondary/tertiary.

The dropped connections come when browsing - from cold, I could ping
with 4096 byte packets quite happily. *ehinfo reports "error
framelen=0" - RMLoad-ing EtherH16 gets things going again. There is
another thread this week reporting some similar symptoms.
I've already got Adjust (ordered in the Feb/March sale :-) but not the
time to fit it :-( until the long weekend.



modem/router gateway setting

Post by Brian Carr » Fri, 14 Apr 2006 18:31:14

In article
< XXXX@XXXXX.COM >, Andrew



I have just had a recurrence of a similar problem on a friend's
network which comprises a PC (WindowsXP), RiscPC (RISC OS 4.39)
and sometimes my PC laptop, all connected to a 4-port
modem/router, thence to Demon broad band.

Problems arose when I tried to get LanMan98 working. Ping OK
everything to every-other-thing /except/ RiscPC -> PC. There
were two blocks on the PC:

'Ping' (ICMP) was disabled in Security_centre ->
Windows_firewall -> Advanced -> ICMP_settings . "Allow incoming
echo requests" has to be ticked.

McAffee Anti-virus was blocking packets sent from the RiscPC.
The latter has to be set up as a trusted source. I have Norton
AV at home which has something similar.

After they were both changed I was able to set up LM98 without
further difficulty.



Brian Carroll, Ripon, North Yorkshire, UK bric at f2s dot com

modem/router gateway setting

Post by Chris Mann » Mon, 17 Apr 2006 18:52:07

> The modem is the bit that connects to the WAN (telephone line) and

I'm tempted by the new broadband offer from Carphone Warehouse, having
had no experience of any networking previously (my Windows box and RPC
communicate only via floppy discs), and they tell me that their modem
connects to "the PC" via USB.

I assume that what I'll need next is something akin to the "Linksys
Wireless-G Broadband Router" which I've found in the Maplin catalogue.
It's described as an "All-in-one Internet-sharing Router, 4-port switch,
and Wireless-G access point", which should suffice for PC and PDA
(wireless), RPC and printer (cable). I presume (it's far from clear)
that the router will attach to the modem via USB?

No doubt you'll all rush to tell me that I've got it all wrong.


modem/router gateway setting

Post by Andrew Wic » Wed, 19 Apr 2006 17:22:55

eh_read" error is symptomatic of a marginal EtherH card. I've now got
a small obey file in $ to RMLoad EtherH16.
Now fitted and running DHCP happily. Still get the framelen error, but
think that's down to the card (though one poster did suggest it went
away when using a different HD!

Thanks again for your interest.


modem/router gateway setting

Post by fornewsgro » Fri, 21 Apr 2006 06:51:30

In message <4E186923F9% XXXX@XXXXX.COM >

Very unlikely, the above type of router is normally used with a cable
modem and ethernet connection, look for a combined adsl router modem
instead of their modem, there may be some routers that will use a usb
modem, can't say I seen any.

John Sandford West Herts UK

Hemel Hempstead RISC OS User Group email info @

modem/router gateway setting

Post by Steven Pam » Fri, 21 Apr 2006 16:04:10

In article <4E186923F9% XXXX@XXXXX.COM >,

The unit you seem to be describing simply connects to the broadband line,
provides four cable ports for things like a print server, a PC, and Iyonix
and a revered old SARPC. Meanwhile the wireless devices (two laptops)
connect from anywhere in the house or nearby.

USB modem? (spit!)

People using USB modems have taken the simple (and less secure) route and
*must* have firewalls running on their PC's or they are in major trouble
virus/trojan wise.

To be honest you have to be a bit dim to leave things that unprotected.

modem/router gateway setting

Post by Tim Hil » Fri, 21 Apr 2006 17:47:21

In article <4E186923F9% XXXX@XXXXX.COM >,

Be prepared to wait. What with BT being inundated with only being able to
MAX less than 100 subscribers per day per exchange, latest estimates are
that new CarPhone customers will be waiting 'til 2007. Apparently
CarPhone's own business plan admits this, though publicly they have said
November 2006.

* Sick of BT? Leave them and reduce your phone bill by up to half.
* Want a spam-proof Usenet address? Visit
or email me: postmaster at invalid dot org dot uk
* ( XXXX@XXXXX.COM is deleted - please use my valid address above)

... "Women may fall when there's no strength in men" Rom & Jul, Act ii, Sc.3

modem/router gateway setting

Post by Chris Evan » Sat, 22 Apr 2006 00:40:50

In article < XXXX@XXXXX.COM >, Steven Pampling

Unfortunatly for them I'm sure there are many users out there who will leave
themselves unprotected, not because they are dim but because they don't
know better, many people in areas they are not expert in, do as is suggested
to them by their supplier, I think it is the supplier who is being

Chris Evans

CJE Micro's / 4D 'RISC OS Specialists'
Telephone: 01903 523222 Fax: 01903 523679
78 Brighton Road, Worthing, West Sussex, BN11 2EN
The most beautiful thing anyone can wear, is a smile!