mac address change on an eth alias

mac address change on an eth alias

[Petre Bandac]

root@k:~# ifconfig eth0:1 123.123.123.123 netmask 255.255.255.0 hw ether 
00:E0:7D:02:C6:0C
SIOCSIFHWADDR: Device or resource busy
root@k:~#

am I trying to do something impossible or is it only my NIC (Realtek 8139) 
that can't do it ?

I want to have 2 ip's on the same interface - but with 2 different macs ... 
why? because this is my testing server and, among others (dhcp, bind, 
sendmail/postfix, asterisk, etc) I want to actually see how a mac address can 
be changed ... if it's possible

thank you for you patience,

petre


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Re: mac address change on an eth alias

[pa3gcu]

On Tuesday 17 December 2002 20:07, Petre Bandac wrote:
> root@k:~# ifconfig eth0:1 123.123.123.123 netmask 255.255.255.0 hw ether
> 00:E0:7D:02:C6:0C
> SIOCSIFHWADDR: Device or resource busy
> root@k:~#
>
> am I trying to do something impossible or is it only my NIC (Realtek 8139)
> that can't do it ?

AFAIK yes, at least the way you are doing it, you can however change a MAC 
adress before configuring the card.

ifconfig eth0 00:E0:7D:02:C6:0C
ifconfig eth0 123.123.123 netmask 255.255.255.0

So what i am saying is, you cant change the MAC address when a IP# is 
assigned.

I tested it on my eth0 interface but without aliasing, but i doubt if that is 
an issue here.

> I want to have 2 ip's on the same interface - but with 2 different macs ...
> why? because this is my testing server and, among others (dhcp, bind,
> sendmail/postfix, asterisk, etc) I want to actually see how a mac address
> can be changed ... if it's possible

Down the IFC's, change the MAC(s), then configure the card and its aliases.

>
> thank you for you patience,
>
> petre

-- 
Regards Richard
pa3gcu@zeelandnet.nl
http://people.zeelandnet.nl/pa3gcu/

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Re: mac address change on an eth alias

[Petre Bandac]

richard, 

thanks for the answer; it is as you said, except I didn't manage to put 2 
different macs

ifconfig eth0 hw ether 00:02:44:11:AA:AA
ifconfig eth0:1 hw ether 00:02:44:11:AA:AB
ifconfig eth0 some_IP netmask 255.255.255.0
ifconfig eth0:1 123.123.123.123 netmask 255.255.255.0

and the result is both have the same mac (the last one issued with ifconfig)

so I didn't get what I wanted - the mac of the alias being different than the 
interface's; should I presume "no can do" ?

thanks,

petre

On Tuesday 17 December 2002 23:14 Anno Domini, pa3gcu wrote using one of his 
keyboards:
> On Tuesday 17 December 2002 20:07, Petre Bandac wrote:
> > root@k:~# ifconfig eth0:1 123.123.123.123 netmask 255.255.255.0 hw ether
> > 00:E0:7D:02:C6:0C
> > SIOCSIFHWADDR: Device or resource busy
> > root@k:~#
> >
> > am I trying to do something impossible or is it only my NIC (Realtek
> > 8139) that can't do it ?
>
> AFAIK yes, at least the way you are doing it, you can however change a MAC
> adress before configuring the card.
>
> ifconfig eth0 00:E0:7D:02:C6:0C
> ifconfig eth0 123.123.123 netmask 255.255.255.0
>
> So what i am saying is, you cant change the MAC address when a IP# is
> assigned.
>
> I tested it on my eth0 interface but without aliasing, but i doubt if that
> is an issue here.
>
> > I want to have 2 ip's on the same interface - but with 2 different macs
> > ... why? because this is my testing server and, among others (dhcp, bind,
> > sendmail/postfix, asterisk, etc) I want to actually see how a mac address
> > can be changed ... if it's possible
>
> Down the IFC's, change the MAC(s), then configure the card and its aliases.
>
> > thank you for you patience,
> >
> > petre

-- 
 23:50:25 up  7:20,  1 user,  load average: 0.02, 0.06, 0.08

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Re: mac address change on an eth alias

[pa3gcu]

On Tuesday 17 December 2002 21:55, Petre Bandac wrote:
> richard,
>
> thanks for the answer; it is as you said, except I didn't manage to put 2
> different macs
>
> ifconfig eth0 hw ether 00:02:44:11:AA:AA
> ifconfig eth0:1 hw ether 00:02:44:11:AA:AB
> ifconfig eth0 some_IP netmask 255.255.255.0
> ifconfig eth0:1 123.123.123.123 netmask 255.255.255.0
>
> and the result is both have the same mac (the last one issued with
> ifconfig)
>
> so I didn't get what I wanted - the mac of the alias being different than
> the interface's; should I presume "no can do" ?

I myself have never used aliasing, i do however need to spoof my MAC 
sometimes on my laptop to be able to use it on other locations for my work.
However thats beside the point, as far as i can see if you set a different 
IP# then the need for another MAC is (AFAIK) not nessasary.
If ARP's are a problem then setting static arps may be an answer, once more i 
have no experiance with alising, possably Ray may have some advise for you.

>
> thanks,
>
> petre
>

-- 
Regards Richard
pa3gcu@zeelandnet.nl
http://people.zeelandnet.nl/pa3gcu/

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Re: mac address change on an eth alias

[Ray Olszewski]

At 10:06 PM 12/17/02 +0000, pa3gcu wrote:
>On Tuesday 17 December 2002 21:55, Petre Bandac wrote:
>[...]
> > so I didn't get what I wanted - the mac of the alias being different than
> > the interface's; should I presume "no can do" ?
>
>I myself have never used aliasing, i do however need to spoof my MAC
>sometimes on my laptop to be able to use it on other locations for my work.
>However thats beside the point, as far as i can see if you set a different
>IP# then the need for another MAC is (AFAIK) not nessasary.
>If ARP's are a problem then setting static arps may be an answer, once more i
>have no experiance with alising, possably Ray may have some advise for you.

Afraid not; I've never actually used aliasing (except in trivial test setups).

Perhaps the best next step would be for you to explain  why you need the 
interfaces to respond as though they were on different physical devices 
(that is, NICs with distinct MAC addresses). With that information, then 
maybe someone here could suggest a workaround. But as far as I know, NICs 
only support a single MAC address at any moment, not multiple ones.


--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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Re: mac address change on an eth alias

[Petre Bandac]

just testing for my general knowledge

I heard that I can change the mac, I did as richard said and it went ok, and 
furthermore I wanted to change the mac of the alias, which I didn't succeed 
(richard's receipt gave the same mac - the mac I specifically assigned to the 
alias - to both IFC and it's alias)

so, I should take the final answer as no ?

thanks,

petre

On Wednesday 18 December 2002 00:53 Anno Domini, Ray Olszewski wrote using one 
of his keyboards:
> At 10:06 PM 12/17/02 +0000, pa3gcu wrote:
> >On Tuesday 17 December 2002 21:55, Petre Bandac wrote:
> >[...]
> >
> > > so I didn't get what I wanted - the mac of the alias being different
> > > than the interface's; should I presume "no can do" ?
> >
> >I myself have never used aliasing, i do however need to spoof my MAC
> >sometimes on my laptop to be able to use it on other locations for my
> > work. However thats beside the point, as far as i can see if you set a
> > different IP# then the need for another MAC is (AFAIK) not nessasary.
> >If ARP's are a problem then setting static arps may be an answer, once
> > more i have no experiance with alising, possably Ray may have some advise
> > for you.
>
> Afraid not; I've never actually used aliasing (except in trivial test
> setups).
>
> Perhaps the best next step would be for you to explain  why you need the
> interfaces to respond as though they were on different physical devices
> (that is, NICs with distinct MAC addresses). With that information, then
> maybe someone here could suggest a workaround. But as far as I know, NICs
> only support a single MAC address at any moment, not multiple ones.

-- 
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Re: mac address change on an eth alias

[pa3gcu]

On Wednesday 18 December 2002 17:46, Petre Bandac wrote:
> just testing for my general knowledge
>
> I heard that I can change the mac, I did as richard said and it went ok,
> and furthermore I wanted to change the mac of the alias, which I didn't
> succeed (richard's receipt gave the same mac - the mac I specifically
> assigned to the alias - to both IFC and it's alias)
>
> so, I should take the final answer as no ?

You have one ethernet card with ONE MAC adress, one can alias an ipadress on 
ones ethernet card, but AFAIK one cannot alias the MAC.

It seems logical, each card has its own MAC adress the adress is stored in a 
chip on the card, note "one adress" an IP# is assigned to a card and linux 
allows aliasing of the IP adress, so i think we must conclude that one cant 
alias the MAC period.

I have done no reading on this as i dont have time, but logicly what is to be 
gained from two MAC addresses on one card, as far as i see it only problems 
would arise, which is possably why it is not done.

>
> thanks,
>
> petre

-- 
Regards Richard
pa3gcu@zeelandnet.nl
http://people.zeelandnet.nl/pa3gcu/

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