I have couple questions regarding MAC address changes:
1) When we change the MAC address, it will change the firmware of NIC,
or just temporary change?
My observation is just temporary change.
2) Do you think changing MAC address can secure the machine more? I
mean at least hackers
cannot keep track on the machines that easily? Well, maybe hackers
should use IP address,
but my observation is that when I change the MAC address, IP address
will change as well.
3) I try it myself, when I change the MAC address, it will change the
IP address as well.
IP address is assigned by ISP, maybe ISP assigns the IP address based
on the MAC address
of the machine as well? MAC address identifies the network card, and IP
address identifies
the computer on the internet.
On 10 Oct 2005 07:42:25 -0700, *email_address_deleted* wrote:
>I have couple questions regarding MAC address changes:
>
>1) When we change the MAC address, it will change the firmware of NIC,
>or just temporary change?
>My observation is just temporary change.
>
>2) Do you think changing MAC address can secure the machine more? I
>mean at least hackers
>cannot keep track on the machines that easily? Well, maybe hackers
>should use IP address,
>but my observation is that when I change the MAC address, IP address
>will change as well.
>
>3) I try it myself, when I change the MAC address, it will change the
>IP address as well.
>IP address is assigned by ISP, maybe ISP assigns the IP address based
>on the MAC address
>of the machine as well? MAC address identifies the network card, and IP
>address identifies
>the computer on the internet.
>
>Please advise. thanks!!
IMHE, changing your MAC address is a useless method of providing security, and
can cause worse problems.
# It is a form of Security by Obscurity.
<http://nitecruzr.blogspot.com/2005/05/security-by-obscurity.html>
# The MAC address is the lowest level identity in networking. See OSI model to
understand this
(<http://nitecruzr.blogspot.com/2005/05/security-by-obscurity.html> for
example). You absolutely must have a unique MAC address on all networked
devices. If you go changing this identity element, and cause a conflict, you
could cause yourself and other people grief.
# If you change your MAC address in an attempt to change your IP address on a
public Internet service, you could cause pain for a few people, including
another subscriber, and the ISP. Changing your IP address is another form of
Security by Obscurity.
--
Cheers,
Chuck, MS-MVP [Windows - Networking] http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
> I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.
As far as I know, it's temporary.
>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.
It makes no difference for security. MAC addresses are relevant only on the
local network. They are discarded as soon as your packets pass through a
router.
>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.
The ISP doesn't assign an IP address based on the MAC address. It assigns a
new address to what appears to be a new computer. It won't reassign the
previous one, until the lease expires.
> You absolutely must have a unique MAC address on all networked
> devices. If you go changing this identity element, and cause a conflict,
> you could cause yourself and other people grief.
The MAC only has to be unique on the local network. It's irrelevant
elsewhere.
1) The MAC address will/should be changed permanently in the firmware. You
need to do this only in special cases, especially when your Internet service
provider instructs you do this!
2) NO! The MAC is not a security service. Whenever the MAC changes, the
network card is told to be a different unit and another IP address is
issued. Use a firewall.
3) See complete description of answer 2. MAC address identifies the PC to
the network. ISP DHCP service locates new MAC address on their systems. IP
address does not identify your PC to the Internet. IP address provides the
"signals" so that your PC can "talk" with the Internet. The IP addresses
identifies your ISP only.
<apngss@yahoo.com> wrote in message
news:1128955345.277201.277310@g49g2000cwa.googlegr oups.com...
>I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.
>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.
>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.
>
> Please advise. thanks!!
>
<apngss@yahoo.com> wrote in message
news:1128955345.277201.277310@g49g2000cwa.googlegr oups.com...
>I have couple questions regarding MAC address changes:
>
> 1) When we change the MAC address, it will change the firmware of NIC,
> or just temporary change?
> My observation is just temporary change.
Temporary.
>
> 2) Do you think changing MAC address can secure the machine more? I
> mean at least hackers
> cannot keep track on the machines that easily? Well, maybe hackers
> should use IP address,
> but my observation is that when I change the MAC address, IP address
> will change as well.
No, I don't see how just changing the MAC address makes much difference.
Since the ISP only controls a range of IP addresses, all a hacker needs to
do is ping everyone of them, and try to penetrate those that respond. This
method would work whether you changed the MAC address or not.
>
> 3) I try it myself, when I change the MAC address, it will change the
> IP address as well.
> IP address is assigned by ISP, maybe ISP assigns the IP address based
> on the MAC address
> of the machine as well? MAC address identifies the network card, and IP
> address identifies
> the computer on the internet.
Perhaps they do. However, this is merely security by obscurity.
Jim
>
> Please advise. thanks!!
>
On Mon, 10 Oct 2005 14:04:07 -0400, James Knott <*email_address_deleted*m>
wrote:
>Chuck wrote:
>
>> You absolutely must have a unique MAC address on all networked
>> devices. If you go changing this identity element, and cause a conflict,
>> you could cause yourself and other people grief.
>
>The MAC only has to be unique on the local network. It's irrelevant
>elsewhere.
What happens if you change it, and cause a conflict with another ISP customer?
Some ISPs that do dynamic addressing hash the MAC address to derive IP address.
BTW, posting your email address openly will get you more unwanted email, than
wanted email. Learn to munge your email address properly, to keep yourself a
bit safer when posting to open forums. Protect yourself and the rest of the
internet - read this article.
<http://nitecruzr.blogspot.com/2005/05/how-to-post-on-usenet-and-encourage.html#Munging>
--
Cheers,
Chuck, MS-MVP [Windows - Networking] http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
On Mon, 10 Oct 2005 14:02:44 -0400, James Knott <*email_address_deleted*> wrote:
>apngss@yahoo.com wrote:
>> 3) I try it myself, when I change the MAC address, it will change the
>> IP address as well.
>> IP address is assigned by ISP, maybe ISP assigns the IP address based
>> on the MAC address
>> of the machine as well? MAC address identifies the network card, and IP
>> address identifies
>> the computer on the internet.
>
>The ISP doesn't assign an IP address based on the MAC address. It assigns a
>new address to what appears to be a new computer. It won't reassign the
>previous one, until the lease expires.
And if you try to connect using a MAC address currently in use by another
customer, what happens? If you appear to be an already known customer
(previously seen MAC address), will it assign the same IP address, will it
declare that IP address in use and assign another address, or wilt it declare an
unidentified problem and maybe disconnect both instances of the same MAC
address?
--
Cheers,
Chuck, MS-MVP [Windows - Networking] http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
Since MAC addresses don't travel off the local area network, unless you
got some VLAN stuff going on, the chances are just a tiny bit small :)
Chuck wrote:
> On Mon, 10 Oct 2005 14:02:44 -0400, James Knott <*email_address_deleted*> wrote:
>
>
>>apngss@yahoo.com wrote:
>
>
>>>3) I try it myself, when I change the MAC address, it will change the
>>>IP address as well.
>>>IP address is assigned by ISP, maybe ISP assigns the IP address based
>>>on the MAC address
>>>of the machine as well? MAC address identifies the network card, and IP
>>>address identifies
>>>the computer on the internet.
>>
>>The ISP doesn't assign an IP address based on the MAC address. It assigns a
>>new address to what appears to be a new computer. It won't reassign the
>>previous one, until the lease expires.
>
>
> And if you try to connect using a MAC address currently in use by another
> customer, what happens? If you appear to be an already known customer
> (previously seen MAC address), will it assign the same IP address, will it
> declare that IP address in use and assign another address, or wilt it declare an
> unidentified problem and maybe disconnect both instances of the same MAC
> address?
>
> And if you try to connect using a MAC address currently in use by another
> customer, what happens? If you appear to be an already known customer
> (previously seen MAC address), will it assign the same IP address, will it
> declare that IP address in use and assign another address, or wilt it
> declare an unidentified problem and maybe disconnect both instances of the
> same MAC address?
On 10 Oct 2005 15:03:03 -0500, Chuck <none@example.net> wrote:
>What happens if you change it, and cause a conflict with another ISP customer?
There are three MAC addresses that you can control. Kindly specify
which one you want to play with.
1. The WAN side MAC address. This is what the ISP uses to assign an
IP address for the ARP table. Every time you change this MAC address,
the DHCP server thinks it's a new computer and will assign a new IP
address. This will drive your ISP nuts. If you duplicate a MAC
address in use at the ISP, your traffic will either stop or get
screwed up. It will also trigger an alarm if they have arpwatch or
some other duplicate MAC/IP address daemon running.
2. The MAC address of your computer on your LAN assuming you have a
router. This can be temporarily changed with a registry tweak. It
does nothing useful as this MAC address is not seen on the internet.
Changing it will temporarily screw up your LAN ARP table but that can
be fixed with:
apr -d your_LAN_IP_address
3. The MAC address of the wireless access point in side your wireless
router. This will cause some confusion to attackers as programs such
as Netstumbler will think there are multiple access points. However,
the same thing will happen to valid wireless users.
>Some ISPs that do dynamic addressing hash the MAC address to derive IP address.
Ummm.... none that I know about.
>BTW, posting your email address openly will get you more unwanted email, than
>wanted email. Learn to munge your email address properly, to keep yourself a
>bit safer when posting to open forums. Protect yourself and the rest of the
>internet - read this article.
><http://nitecruzr.blogspot.com/2005/05/how-to-post-on-usenet-and-encourage.html#Munging>
Have you verified that as true? I have 3 mailboxes that I have used
since the stone age of the internet (when it was all Usenet, there was
no web, and everything ran on Telebit modems with UUCP). I have never
bothered to mung, mutilate, or otherwise hide my email addresses. I
get no more junk email than any of my friends and accomplises that go
through rediculous exercises to avoid the spammers. If you want to
get rid of spam, start here: http://www.spamhaus.org/rokso/index.lasso
and take out a few of these turkeys.
[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]
In <o6cmk154efm0c0o5gg8vq4cpa0tirt5h6g@4ax.com> on Mon, 10 Oct 2005 20:37:34
-0700, Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:
>On 10 Oct 2005 15:03:03 -0500, Chuck <none@example.net> wrote:
>>BTW, posting your email address openly will get you more unwanted email, than
>>wanted email. Learn to munge your email address properly, to keep yourself a
>>bit safer when posting to open forums. Protect yourself and the rest of the
>>internet - read this article.
>><http://nitecruzr.blogspot.com/2005/05/how-to-post-on-usenet-and-encourage.html#Munging>
>
>Have you verified that as true? I have 3 mailboxes that I have used
>since the stone age of the internet (when it was all Usenet, there was
>no web, and everything ran on Telebit modems with UUCP). I have never
>bothered to mung, mutilate, or otherwise hide my email addresses. I
>get no more junk email than any of my friends and accomplises that go
>through rediculous exercises to avoid the spammers. ...
It's amazing to me how many urban legends are passed around the Internet that
have no sound basis. This is one of them.
--
Best regards, HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas <http://navasgrp.home.att.net/#Cingular>
On Mon, 10 Oct 2005 23:01:05 +0100, Steve Welsh <nobody@linux.bogus> wrote:
>Chuck wrote:
>> On Mon, 10 Oct 2005 14:02:44 -0400, James Knott <*email_address_deleted*> wrote:
>>
>>
>>>apngss@yahoo.com wrote:
>>
>>
>>>>3) I try it myself, when I change the MAC address, it will change the
>>>>IP address as well.
>>>>IP address is assigned by ISP, maybe ISP assigns the IP address based
>>>>on the MAC address
>>>>of the machine as well? MAC address identifies the network card, and IP
>>>>address identifies
>>>>the computer on the internet.
>>>
>>>The ISP doesn't assign an IP address based on the MAC address. It assigns a
>>>new address to what appears to be a new computer. It won't reassign the
>>>previous one, until the lease expires.
>>
>>
>> And if you try to connect using a MAC address currently in use by another
>> customer, what happens? If you appear to be an already known customer
>> (previously seen MAC address), will it assign the same IP address, will it
>> declare that IP address in use and assign another address, or wilt it declare an
>> unidentified problem and maybe disconnect both instances of the same MAC
>> address?
>Since MAC addresses don't travel off the local area network, unless you
>got some VLAN stuff going on, the chances are just a tiny bit small :)
Yup. And the smaller they are (but not zero), the longer it's gonna take your
typical clueless ISP support staff to realise that that's the cause of the
problem!
--
Cheers,
Chuck, MS-MVP [Windows - Networking] http://nitecruzr.blogspot.com/
Paranoia is not a problem, when it's a normal response from experience.
My email is AT DOT
actual address pchuck mvps org.
In the Usenet newsgroup alt.internet.wireless, in article
<7qhlk1tmnkon0jeccv7210j6892kbmts6i@4ax.com>, Chuck wrote:
>James Knott <*email_address_deleted*m> wrote:
>>
>>Chuck wrote:
>>
>>> You absolutely must have a unique MAC address on all networked
>>> devices.
>>The MAC only has to be unique on the local network. It's irrelevant
>>elsewhere.
>What happens if you change it, and cause a conflict with another ISP
>customer?
What James means is that all Network Interface Cards that can talk
_DIRECTLY_ to each other need to be unique. On your LAN, that means
all hosts on "this" side of the router. There is nothing wrong with
having the identical MAC address on the "other" side of the router.
In a Sun workstation, _all_ network interfaces have the same MAC
address (it's determined by a parameter in the equivalent of the
BIOS on the motherboard, _not_ the network card). So, I've got a
Sun box with three network interfaces (to three different subnets)
and they all have the same MAC, though "different" IP addresses like
192.0.2.35/24 on hme0, 198.18.10.35/24 on hme1, and 198.18.24.35 on
hme2.
>Some ISPs that do dynamic addressing hash the MAC address to derive IP
>address.
Cite please. (Honest and true - no one uses a hash of the MAC,
because of the way MAC addresses are allocated, verses the size
of an IP subnet.) Just for jollies, as of the first of this month,
there are 8643 OUI assignments (the top 24 bits of the MAC address).
These are scattered in a semi-haphazard way from 00:00:00: which is
assigned to Xerox, to AC:DE:48: which is assigned to a private
entity. The assignment of the lower 24 bits of the MAC address are
totally at the pleasure of the assignee - if they want to start at
:00:00:00 and increment up or at :FF:FF:FF and work down - or both,
or something else entirely, that's fine with the IEEE. All they care
is that you don't duplicate an address (although that has happened
on a lot more than one occasion).
What you may be thinking is 'pre-assigned' addresses in DHCP, where
the poor sod who has to configure that abomination manually assigned
a MAC:IP address combination in the configuration file. Thus, when a
host with MAC address of 08:00:20:E7:54:8A comes up, the DHCP server
knows that this host is to get "that" address, and no one else.
kshetu@gmail.com wrote:
> hi!,
> i chnage the mac address for my computer. but now i can not accsess the
> net. what happend on mac address. i have a fixed ip.
>
Hi,
Your ISP may expect your old MAC address. Some ISP wants one registered
MAC address all the time. Talked to your ISP tech support?
My ISP does not care about MAC address.
Tony
changing MAC address questions 
Linear Mode
