I have seen several posts in this group asking if NTL only allow
access from one registered MAC address.

During last weeks storms, the Ethernet port on my Netgear WGR614
router blew (as did the 3COM card in my PC and the 3 ports that were
in use on my 3COM switch). I connected the replacement router to my
cable modem last night and was able to access my NTL broadband line
(and the Internet) immediately.

So, it would appear that access on an NTL broadband line is not fixed
to a registered MAC address.

Pete

Partially correct, but I suspect also partially not. It's over a year since
I ws on NTL so things nmay have changed but ...

For one thing, remember that NTL has taken over various cable systems in the
past, and I believe that there are still legacy diifferences in
configuration.

I live in Berks, and for this area what I was told by an NTL support
engineer (which I certainly wouldn't automatically believe but it fits
exactly with my experiences so I guess he was right :-) is:

Your equipment is connected to NTL via a cable modem, which can be regarded
as negotiating access with NTL on one side of it on behalf of your equipment
on the other. When it connects to NTL, it leases via DHCP an IP address for
your equipment, and *for the duration of that lease* that particular IP is
bound to that particular MAC address of your equipment. ATT I deduced from
my experiences that this binding is stored on the server, not the cable
modem, otherwise it would be lost by just switching off the latter.

In your particular case, presumably so much time had elapsed without your
old equipment being present that its last IP lease had long expired, so you
had no problems connecting different equipment, but others who, say, wish to
start using a router may well find that they cannot just insert the router
in between their PC and their cable modem because its MAC address will be
different. To use the router they will have to do one of:

1) If the cable modem supports it (mine didn't but my boss's apparently
did), get it to release the IP address thus clearing the binding on the
server, then they should be able to connect up the new configuration
immediately, but I was never able to verify this.

2) Switch off the cable modem until the server notices that it has gone
away and releases the IP binding (ISTR 30 mins should do the trick), then
connect up the new configuration.

3) A variant on 2) is noting your old MAC and IP, ringing up Support, and
asking them to clear the binding, but you'll often spend so much time on the
phone that it would have cleared anyway!

4) Connect it all up anyway and just wait (possibly several hours,
overnight should do it) for the lease to expire and be renewed, but why not
do 2) in this case?

5) If the router supports it, get it to mimic the MAC address of the PC,
then they can reconnect immediately.

My favoured option theoretically was 1), but in practice was 2).

"Pete Mainwaring" <peter.mainwaring@virgin.net> wrote in message
news:64d77c87.0408100011.189bb69b@posting.google.c om...

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No you do not have to register the MAC address, just need to reboot the
modem

---------------------------------------
www.chetnet.co.uk/portal
Cable support without the politics
And first class too
---------------------------------------


"Pete Mainwaring" <peter.mainwaring@virgin.net> wrote in message
news:64d77c87.0408100011.189bb69b@posting.google.c om...

On 10 Aug 2004 01:11:35 -0700, peter.mainwaring@virgin.net (Pete
Mainwaring) wrote:

They do.

It is The MAC address that is fixed is that of your cable modem
which does the negotiation with the network first, then talks to the
router independently. So, you can have infinite router changes without
notifiying ntl, but change the modem and you'll need to call their CS.

"Java Jive" <java@evij.com> wrote in message news:<Y7KdnZhsi4ZUAoXcRVn-hQ@nildram.net>...
Yes - that is a good point. My router was "off air" for 4 days in
total, so any ARP binding would probably have been aged out. I guess
the problem occurs if someone just replaces one peice of equipment
with another in a short period of time.

However, my experience does seem to prove that the MAC address issue
is more to do with ARP binding rather than actually registering a MAC
address.

Pete

On 10 Aug 2004 01:11:35 -0700, peter.mainwaring@virgin.net (Pete
Mainwaring) wrote:

you can connect up to 3 different MACs (only one at a time of course).
If you try to connect a 4th, it will get rejected until some timeout
has expired on one of the other three.

This has been the case for at least 2 years !

Mark McIntyre <markmcintyre@spamcop.net> wrote in message news:<0ciih09d48n6cf64seq0d0ioi6bk7dt6b5@4ax.com>. ..
So we have a slight difference of opinion. Mark says that NTL haven't
required a registered MAC address for the last 2 years and Richard
says it is fixed to the MAC address of the cable modem.

If the cable modem does have a MAC address of its own, how does it
work? (This is a genuine question - I'm not trying to be awkward
here). Is it some sort of layer 2 relay? If that is the case, does it
have an IP address of its own too? (that presumably would be hidden
from the customer and would be just for NTL management). Or does it
act like a bridge where it passes user MAC addresses through, but also
sends some sort of BPDU packets (just as a LAN bridge does) to the
other end to handle the MAC address registration?

If the cable modem is effectively a bridge, then I guess you are both
correct. The cable modem is the registered NTL MAC address and that
means that the user can change routers, PC's etc quite happily, but
only up to the limit that NTL allow in the ARP table (or equivalent)
because the user equipment doesn't have to be registered.

Also, if you can connect up to 3 MAC adresses in quick succession to
the cable and they all work, could you connect a switch to the cable
modem and run 3 PCs simultaneously? (Not that I would want to do that
personally, I'll stick to my router, I was just interested from a
theoretical point of view).

Pete

On Tue, 10 Aug 2004 20:11:12 +0100, chris <see@reply.to.field> wrote:

/shrug. When I was a lad... <g>

On 11 Aug 2004 01:28:47 -0700, peter.mainwaring@virgin.net (Pete
Mainwaring) wrote:

When I registered they insisted on taking the MAC address of the modem
otherwise it wouldn't work. It seems this has now changed, but since
I've only ever had one modem, I wouldn't have known

no, you'd need a router since you only get a single IP from ntl.

"chris" <see@reply.to.field> wrote in message
news:MPG.1b8325c6daa69390989f22@news.clara.net...
I think there is some confussion over the MAC address of say a network card
and that of the NTL supplied modem?

You can have several machines and attach them without problems to a set-top
box, but if you then add anther machine or change one of the "registered"
machines NICs in a short space of times you may encounter a problem.

Changing the set-top box or NTL supplied modem would also require
re-registration, unless that modem were already registered.

Regards - Keef
--
Dartford Kent UK
Email hk11WRAPPER@jcdigita.com
(To reply, remove the WRAPPER)
Web: http://homepage.ntlworld.com/k.hallock/fsale.html

In article <64d77c87.0408110028.67c2c923@posting.google.com>,
Pete Mainwaring <peter.mainwaring@virgin.net> wrote:
There any many different variations.

Yes, the cable modem is what's termed an "associative bridge". It bridges
networks using different transport media transparently ("bridge") by
transmitting all packets it sees from the very first MAC address it sees
on its Ethernet interface down the HFC interface ("associative").

If you unplug PC1 and plug in PC2, the modem won't bridge its packets
because it isn't the MAC it saw first - you have to then reboot. In some
areas ntl have set the modems to be able to learn two MAC addresses, in
which case you can do this with two devices, but not three.

Yes, the cable modem has its own MAC and IP address. Most have two - a
LAN-side address eg 192.168.100.1 for the Ambits, and an HFC-side one;
mine's 10.247.xx.xx (used to be in the 172.25.76.xx range).

The way it works is that the DHCP server that serves your PC or router's
request for an IP address checks the MAC address of the modem (the
Universal Broadband Route = uBR passes this through). If your MAC address
is not registered, it hands you an IP address that can only route to the
autoreg.autoregister.net server where you can register; if your MAC
address is registered, then you get an IP address that ntl: will route.

Yes, as described above.

No - because the modem is not a router each device on the switch needs its
own public IP address, and ntl gives out only one IP address per
subscriber.

Zane.

abuse@wilson.st () wrote in message news:<f81pu1-j93.ln1@news.wilson.st>...
Very informative answers. Thanks Richard and Zane. That pretty much
explains everything anyone would need to know about how it all works.

Pete

(PS - Sorry if this post appears twice - I got an error when I tried
to post the message first time)

No; which is useful, as you can use your broadband on different computers if
you don't have a home network.

However, the modem is 'bound' to the current one you're using for the
duration of your usage of it (nice grammar Davey-boi....) - basically you
can use another NIC with the modem and it'll work, very nice of NTL to allow
that, as i've had to change what computer the broadband's on, save's calling
up all the time.

"Pete Mainwaring" <peter.mainwaring@virgin.net> wrote in message
news:64d77c87.0408100011.189bb69b@posting.google.c om...