🚀 go-pugleaf

In message <BRrxlpGi$M97EwcK@jimsmith.demon.co.uk>, Jim Smith 
<jim@jimsmith.demon.co.uk> writes
>I have a W2K server with a cable modem and an ISDN card. I have a 
>number of other machines on an Ethernet network (W2K Professional and 
>Linux) which use the W2K server as a gateway.
>
>The cable modem appears to W2K as an Ethernet port and gets its IP 
>configuration, including default gateway and DNS servers via DHCP from 
>the cable provider.    I have set up network address translation on the 
>W2K machine and set the default gateway on the other machines to the 
>W2K machine.

To be honest, I'd use the Linux box to do the NAT rather than W2K Server 
- but that's your choice. I think you're going to get finer control 
using the Linux box, and I think you may need that control here, though, 
to be fair, I have never set up a Linux box as a router.


>This all worked perfectly until the other day when I tried to set up a 
>demand-dial interface on ISDN so I could collect mail and news from my 
>ISP (Demon) using dial-up (you have to dial-up to demon to use their 
>mail and news).

No - you don't. You can collect mail from Demon using POP3 from any ISP, 
though you will have to set your POP3 password at 
<https://www.password.uk.demon.net> first.

Demon's news server is nothing special, though, to be fair, neither is 
ntl:'s. Also ntl:'s SMTP smart host has been playing up recently - see 
ntl.support.broadband.cm passim. I avoid the lot and use machines at 
gradwell.com - but that's an option that costs money.


I'm bemused as to how you set up a dial on demand interface to Demon in 
the situation when you want the majority of your ISP traffic to go over 
ntl: - unless, of course, W2K Server has some feature that I've 
forgotten about. I know the networking features in W2K Server are more 
capable than W2K Professional - I only regularly use Professional.


>This seemed to work initially but then started to fail intermittently. 
>I took out the demand dial interface, but the problems persisted.

It sounds like you've got a default gateway problem. Assuming you want 
the bulk of your network traffic to go via the cable modem you do want 
the default gateway set by DHCP on the cable modem (I don't understand 
the other poster's advice here).


The problem is how do you install the routes to Demon's network. From 
memory, you can either have "Use default gateway on remote network" 
(connection properties, Networking tab, TCP/IP, Properties button, 
Advanced... button, General tab) checked or not. I'm pretty sure W2K 
Server is similar to the W2K Professional machine that I'm looking at.

If that button is checked, then a default route will be installed to the 
default gateway at Demon, and this is done in such a way that it has 
higher priority (lower metric) than the default gateway on any of your 
LAN cards (including the USB connected cable modem).

If that button is not checked, then the connection will basically not be 
used - from memory, you get a route to whatever subnet is defined by the 
IP address and netmask returned by the PPP negotiation. You'll need to 
install further routes so that traffic to Demon's machines to get any 
useful traffic over the dial up link. Unless W2K Server has extra 
features over W2K Professional that I've forgotten about, the only way I 
can think of this is static routes pointing at the interface number of 
the dial-up adapter - though I'd expect this will foul up the dial on 
demand. It's for this reason I was thinking of using the Linux box - you 
should have the route commands in a shell script for use when the ISDN 
connection is brought up.


>The situation now is that external connectivity from any of my 
>workstations is up and down like a yo-yo.  The situation can change 
>from second to second but as far as I can tell, by turning round and 
>doing the same thing on the gateway machine, the problem is internal 
>rather than external (although of course by the time I turn round the 
>situation may have changed).

Are you absolutely sure that the dial on demand has been disabled? If 
your default gateway keeps getting changed, that could cause this 
symptom. Further, I'm not sure how well the NAT functions in W2K Server 
cope with being used in this kind of scenario, because I've never used 
them like this.

I use hardware routers - a Netgear RO318 on the cable modem and a 3Com 
OfficeConnect Remote 511s on the ISDN side. However, I've now got 
everything I need operating over the cable modem and the ISDN router is 
sat in the junk box. Certainly a box like the 3Com on your LAN should 
solve at least the ISDN side of the problem - not least because it can 
advertise the routes it has available via ISDN using RIP, and that works 
fine with W2K's RIP listener.


>I have a number of ideas about possible causes, but am at a loss on how 
>to investigate further. I need some guidance on tools and techniques to 
>try to pin it down.

I'd guess a combination of "route print" on the gateway machine coupled 
with judicious use of ping or tracert to various external machines will 
show what's happening on the gateway machine. Once you understand the 
behaviour there, you can then start wondering about what's happening to 
the other machines on the LAN.


>One potential problem is either the reliability of, or routing to, my 
>providers DNS servers.  Is there a set of alternative DNS servers I can 
>use to help distinguish? Can I use demon DNS servers when not dialled 
>up to demon?

You can, though I'm bemused as to why you think DNS servers are part of 
the problem. ntl:'s DNS servers have been a bit troublesome - but I 
can't see how this would explain the problems you're talking about. 
Failure to resolve names to IP addresses - yes - that's a DNS problem 
for sure.


>How can I pin down the routing problem to internal or external?
>
>If it is internal how can I diagnose the cause in the W2K server?

As you can tell, my expertise with RRAS (the NAT functions) and dial on 
demand in W2K Server is almost nil, and I know it's different to W2K 
Professional - but I hope there's some pointers here.



David
-- 
David Wood
david@wood2.org.uk