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MAC Bridge Miniport, duplicate MACs on LAN

Source: microsoft.public.virtualpc
Sent: 04/26/2006
From: Tony Gravagno <(email address - cut out)lid>
Message:

We run VPC on more than one real XP PC. To get network access from a
VPC I have a Loopback Adapter bridged under the MAC Bridge
MiniAdapter, and then I bridge the real NIC with those. Each adapter
has a different IP, for a total of 3 IP's per real PC. When they are
all bridged the only IP and MAC address that is visible to the network
is that of the MAC Bridge Miniport adapter. Even though I assign a
unique IP, this adapter has a hardcoded MAC address:
02-00-4c-4f-4f-50 (which for geeks that translates to...)
smiley null L-O-O-P

If I have one PC running this configuration with VPC, there is no
problem, VPC communicates with the LAN and WAN just like any real PC.
If I have two PCs with this configuration, even through the IP
addresses are static and different, the MAC is still the same.

Here's the kicker: When my router sees two systems with the same MAC
address it locks up the whole network. This happened with a Linksys
BEFSX41 (with decent firmware). But the first time it happened I
thought the router was going bad, so rather than buy another hardware
router I converted an old PC into a router using IPCOP freeware - and
after all of the effort to build that box the same thing happened to
it as soon as we brought up VPC on a second box. The good news is
that now we have two good router/firewalls. :)

To the questions:
- For anyone else running VPC concurrently on different real PCs in
the same network, how do you avoid this MAC address issue?
- Is there a better way to configure networking with VPC on the host
so that we still get access from guest to host/LAN/WAN?
- Might we be able to use one of the routers now to masquerade the MAC
of one of the boxes? (I'm not a networking guy so this is a shot in
the dark.) This isn't a real solution - what about those people who
run 50 VPCs in the same network?
- Looking at Settings for our VPC's I see the "Network" setting shows
the name of the real NIC, but the .VMC file shows the MAC Bridge
Miniport down in the ethernet_adapter node. There is only one
controller there. Is this a clue to a misconfiguration? We have
several VPC guests working this way.

Thanks!

Post Reply | This is Spam! | Mark as Spam

Related Messages

Re: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 04/27/2006
From: Tony Gravagno <(email address - cut out)lid>
Message:

As I recall that doesn't allow interaction between Guest and host or
LAN. Is that incorrect? I did this as a specific solution to a
problem but that was so long ago that now it's the way I set up all of
the VPC guest/host configs, and until now there hasn't been a problem.
Coincidentally we just never ran VPC on two hosts simultaneously and
connections are unbridged when VPC isn't in use.

Hoping for more input but thanks.

"Ken Schaefer" <(email address - cut out)> wrote:

Show quoted text

>Why do you need the Loopback Adapter + Bridge?
>
>Why not just assign the virtual adapter to the physical wired adapter?
>
>Cheers
>Ken
>
>"Tony Gravagno" <(email address - cut out)lid> wrote in message
>news:(email address - cut out)...
>> We run VPC on more than one real XP PC. To get network access from a
>> VPC I have a Loopback Adapter bridged under the MAC Bridge
>> MiniAdapter, and then I bridge the real NIC with those. Each adapter
>> has a different IP, for a total of 3 IP's per real PC. When they are
>> all bridged the only IP and MAC address that is visible to the network
>> is that of the MAC Bridge Miniport adapter. Even though I assign a
>> unique IP, this adapter has a hardcoded MAC address:
>> 02-00-4c-4f-4f-50 (which for geeks that translates to...)
>> smiley null L-O-O-P
>>
>> If I have one PC running this configuration with VPC, there is no
>> problem, VPC communicates with the LAN and WAN just like any real PC.
>> If I have two PCs with this configuration, even through the IP
>> addresses are static and different, the MAC is still the same.
>>
>> Here's the kicker: When my router sees two systems with the same MAC
>> address it locks up the whole network. This happened with a Linksys
>> BEFSX41 (with decent firmware). But the first time it happened I
>> thought the router was going bad, so rather than buy another hardware
>> router I converted an old PC into a router using IPCOP freeware - and
>> after all of the effort to build that box the same thing happened to
>> it as soon as we brought up VPC on a second box. The good news is
>> that now we have two good router/firewalls. :)
>>
>> To the questions:
>> - For anyone else running VPC concurrently on different real PCs in
>> the same network, how do you avoid this MAC address issue?
>> - Is there a better way to configure networking with VPC on the host
>> so that we still get access from guest to host/LAN/WAN?
>> - Might we be able to use one of the routers now to masquerade the MAC
>> of one of the boxes? (I'm not a networking guy so this is a shot in
>> the dark.) This isn't a real solution - what about those people who
>> run 50 VPCs in the same network?
>> - Looking at Settings for our VPC's I see the "Network" setting shows
>> the name of the real NIC, but the .VMC file shows the MAC Bridge
>> Miniport down in the ethernet_adapter node. There is only one
>> controller there. Is this a clue to a misconfiguration? We have
>> several VPC guests working this way.
>>
>> Thanks!
>

Re: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 04/27/2006
From: "Ken Schaefer" <(email address - cut out)>
Message:

Why do you need the Loopback Adapter + Bridge?

Why not just assign the virtual adapter to the physical wired adapter?

Cheers
Ken

"Tony Gravagno" <(email address - cut out)lid> wrote in message
news:(email address - cut out)...

Show quoted text

> We run VPC on more than one real XP PC. To get network access from a
> VPC I have a Loopback Adapter bridged under the MAC Bridge
> MiniAdapter, and then I bridge the real NIC with those. Each adapter
> has a different IP, for a total of 3 IP's per real PC. When they are
> all bridged the only IP and MAC address that is visible to the network
> is that of the MAC Bridge Miniport adapter. Even though I assign a
> unique IP, this adapter has a hardcoded MAC address:
> 02-00-4c-4f-4f-50 (which for geeks that translates to...)
> smiley null L-O-O-P
>
> If I have one PC running this configuration with VPC, there is no
> problem, VPC communicates with the LAN and WAN just like any real PC.
> If I have two PCs with this configuration, even through the IP
> addresses are static and different, the MAC is still the same.
>
> Here's the kicker: When my router sees two systems with the same MAC
> address it locks up the whole network. This happened with a Linksys
> BEFSX41 (with decent firmware). But the first time it happened I
> thought the router was going bad, so rather than buy another hardware
> router I converted an old PC into a router using IPCOP freeware - and
> after all of the effort to build that box the same thing happened to
> it as soon as we brought up VPC on a second box. The good news is
> that now we have two good router/firewalls. :)
>
> To the questions:
> - For anyone else running VPC concurrently on different real PCs in
> the same network, how do you avoid this MAC address issue?
> - Is there a better way to configure networking with VPC on the host
> so that we still get access from guest to host/LAN/WAN?
> - Might we be able to use one of the routers now to masquerade the MAC
> of one of the boxes? (I'm not a networking guy so this is a shot in
> the dark.) This isn't a real solution - what about those people who
> run 50 VPCs in the same network?
> - Looking at Settings for our VPC's I see the "Network" setting shows
> the name of the real NIC, but the .VMC file shows the MAC Bridge
> Miniport down in the ethernet_adapter node. There is only one
> controller there. Is this a clue to a misconfiguration? We have
> several VPC guests working this way.
>
> Thanks!

Re: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 04/28/2006
From: "Ken Schaefer" <(email address - cut out)>
Message:

Hi,

If you assign the virtual adapter to the physical one, that does allow
interaction between guest, host and LAN.

The only caveat is that the virtual adapter needs to have an address that's
valid on the network (e.g. if you have a TCP/IP network, the virtual adapter
needs to have an IP address that is valid).

If you have a DHCP server, then the virtual adapter can/will pick up an IP
address from the DHCP server. If you don't, you will need to assign a valid
static IP address to the virtual adapter inside the VPC

Cheers
Ken

"Tony Gravagno" <(email address - cut out)lid> wrote in message
news:(email address - cut out)...

Show quoted text

> As I recall that doesn't allow interaction between Guest and host or
> LAN. Is that incorrect? I did this as a specific solution to a
> problem but that was so long ago that now it's the way I set up all of
> the VPC guest/host configs, and until now there hasn't been a problem.
> Coincidentally we just never ran VPC on two hosts simultaneously and
> connections are unbridged when VPC isn't in use.
>
> Hoping for more input but thanks.
>
> "Ken Schaefer" <(email address - cut out)> wrote:
>
>>Why do you need the Loopback Adapter + Bridge?
>>
>>Why not just assign the virtual adapter to the physical wired adapter?
>>
>>Cheers
>>Ken
>>
>>"Tony Gravagno" <(email address - cut out)lid> wrote in message
>>news:(email address - cut out)...
>>> We run VPC on more than one real XP PC. To get network access from a
>>> VPC I have a Loopback Adapter bridged under the MAC Bridge
>>> MiniAdapter, and then I bridge the real NIC with those. Each adapter
>>> has a different IP, for a total of 3 IP's per real PC. When they are
>>> all bridged the only IP and MAC address that is visible to the network
>>> is that of the MAC Bridge Miniport adapter. Even though I assign a
>>> unique IP, this adapter has a hardcoded MAC address:
>>> 02-00-4c-4f-4f-50 (which for geeks that translates to...)
>>> smiley null L-O-O-P
>>>
>>> If I have one PC running this configuration with VPC, there is no
>>> problem, VPC communicates with the LAN and WAN just like any real PC.
>>> If I have two PCs with this configuration, even through the IP
>>> addresses are static and different, the MAC is still the same.
>>>
>>> Here's the kicker: When my router sees two systems with the same MAC
>>> address it locks up the whole network. This happened with a Linksys
>>> BEFSX41 (with decent firmware). But the first time it happened I
>>> thought the router was going bad, so rather than buy another hardware
>>> router I converted an old PC into a router using IPCOP freeware - and
>>> after all of the effort to build that box the same thing happened to
>>> it as soon as we brought up VPC on a second box. The good news is
>>> that now we have two good router/firewalls. :)
>>>
>>> To the questions:
>>> - For anyone else running VPC concurrently on different real PCs in
>>> the same network, how do you avoid this MAC address issue?
>>> - Is there a better way to configure networking with VPC on the host
>>> so that we still get access from guest to host/LAN/WAN?
>>> - Might we be able to use one of the routers now to masquerade the MAC
>>> of one of the boxes? (I'm not a networking guy so this is a shot in
>>> the dark.) This isn't a real solution - what about those people who
>>> run 50 VPCs in the same network?
>>> - Looking at Settings for our VPC's I see the "Network" setting shows
>>> the name of the real NIC, but the .VMC file shows the MAC Bridge
>>> Miniport down in the ethernet_adapter node. There is only one
>>> controller there. Is this a clue to a misconfiguration? We have
>>> several VPC guests working this way.
>>>
>>> Thanks!
>>
>

Re: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 04/28/2006
From: "Bill Grant" <not.available@online>
Message:

I suggest you give it a try. If you set the vm's NIC to the physical NIC
option, the vm should look just like another machine on the network. Your
router should see it as a separate machine with its own MAC address. I have
several machines running VPC or virtual server running like this behind a
D-Link router and have never had any problems. Problems do arise if you are
using wireless NICs (because the do not support promiscuous mode).

I have never been able to get this to work on my Thinkpad using the
wireless NIC. The vm can see the network but it can't see the host.

Tony Gravagno wrote:

Show quoted text

> As I recall that doesn't allow interaction between Guest and host or
> LAN. Is that incorrect? I did this as a specific solution to a
> problem but that was so long ago that now it's the way I set up all of
> the VPC guest/host configs, and until now there hasn't been a problem.
> Coincidentally we just never ran VPC on two hosts simultaneously and
> connections are unbridged when VPC isn't in use.
>
> Hoping for more input but thanks.
>
> "Ken Schaefer" <(email address - cut out)> wrote:
>
>> Why do you need the Loopback Adapter + Bridge?
>>
>> Why not just assign the virtual adapter to the physical wired
>> adapter?
>>
>> Cheers
>> Ken
>>
>> "Tony Gravagno" <(email address - cut out)lid> wrote in
>> message news:(email address - cut out)...
>>> We run VPC on more than one real XP PC. To get network access from
>>> a VPC I have a Loopback Adapter bridged under the MAC Bridge
>>> MiniAdapter, and then I bridge the real NIC with those. Each
>>> adapter has a different IP, for a total of 3 IP's per real PC.
>>> When they are all bridged the only IP and MAC address that is
>>> visible to the network is that of the MAC Bridge Miniport adapter.
>>> Even though I assign a unique IP, this adapter has a hardcoded MAC
>>> address: 02-00-4c-4f-4f-50 (which for geeks that translates to...)
>>> smiley null L-O-O-P
>>>
>>> If I have one PC running this configuration with VPC, there is no
>>> problem, VPC communicates with the LAN and WAN just like any real
>>> PC. If I have two PCs with this configuration, even through the IP
>>> addresses are static and different, the MAC is still the same.
>>>
>>> Here's the kicker: When my router sees two systems with the same MAC
>>> address it locks up the whole network. This happened with a Linksys
>>> BEFSX41 (with decent firmware). But the first time it happened I
>>> thought the router was going bad, so rather than buy another
>>> hardware router I converted an old PC into a router using IPCOP
>>> freeware - and after all of the effort to build that box the same
>>> thing happened to it as soon as we brought up VPC on a second box.
>>> The good news is that now we have two good router/firewalls. :)
>>>
>>> To the questions:
>>> - For anyone else running VPC concurrently on different real PCs in
>>> the same network, how do you avoid this MAC address issue?
>>> - Is there a better way to configure networking with VPC on the host
>>> so that we still get access from guest to host/LAN/WAN?
>>> - Might we be able to use one of the routers now to masquerade the
>>> MAC of one of the boxes? (I'm not a networking guy so this is a
>>> shot in the dark.) This isn't a real solution - what about those
>>> people who run 50 VPCs in the same network?
>>> - Looking at Settings for our VPC's I see the "Network" setting
>>> shows the name of the real NIC, but the .VMC file shows the MAC
>>> Bridge Miniport down in the ethernet_adapter node. There is only
>>> one controller there. Is this a clue to a misconfiguration? We
>>> have several VPC guests working this way.
>>>
>>> Thanks!

Re: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 05/02/2006
From: Tony Gravagno <(email address - cut out)lid>
Message:

Referencing the physical NIC does cover everything. I don't
understand why it never used to work, so I've been doing the
bridge/loopback thing for a couple years. *sigh*

Thanks heaps guys!

"Ken Schaefer" wrote:

Show quoted text

>Hi,
>
>If you assign the virtual adapter to the physical one, that does allow
>interaction between guest, host and LAN.
>
>The only caveat is that the virtual adapter needs to have an address that's
>valid on the network (e.g. if you have a TCP/IP network, the virtual adapter
>needs to have an IP address that is valid).
>
>If you have a DHCP server, then the virtual adapter can/will pick up an IP
>address from the DHCP server. If you don't, you will need to assign a valid
>static IP address to the virtual adapter inside the VPC
>
>Cheers
>Ken
>
>"Tony Gravagno" wrote
>> As I recall that doesn't allow interaction between Guest and host or
>> LAN. Is that incorrect? I did this as a specific solution to a
>> problem but that was so long ago that now it's the way I set up all of
>> the VPC guest/host configs, and until now there hasn't been a problem.
>> Coincidentally we just never ran VPC on two hosts simultaneously and
>> connections are unbridged when VPC isn't in use.
>>
>> Hoping for more input but thanks.
>>
>> "Ken Schaefer" wrote:
>>
>>>Why do you need the Loopback Adapter + Bridge?
>>>
>>>Why not just assign the virtual adapter to the physical wired adapter?
>>>
>>>Cheers
>>>Ken
>>>
>>>"Tony Gravagno" wrote
>>>> We run VPC on more than one real XP PC. To get network access from a
>>>> VPC I have a Loopback Adapter bridged under the MAC Bridge
>>>> MiniAdapter, and then I bridge the real NIC with those. Each adapter
>>>> has a different IP, for a total of 3 IP's per real PC. When they are
>>>> all bridged the only IP and MAC address that is visible to the network
>>>> is that of the MAC Bridge Miniport adapter. Even though I assign a
>>>> unique IP, this adapter has a hardcoded MAC address:
>>>> 02-00-4c-4f-4f-50 (which for geeks that translates to...)
>>>> smiley null L-O-O-P
>>>>
>>>> If I have one PC running this configuration with VPC, there is no
>>>> problem, VPC communicates with the LAN and WAN just like any real PC.
>>>> If I have two PCs with this configuration, even through the IP
>>>> addresses are static and different, the MAC is still the same.
>>>>
>>>> Here's the kicker: When my router sees two systems with the same MAC
>>>> address it locks up the whole network. This happened with a Linksys
>>>> BEFSX41 (with decent firmware). But the first time it happened I
>>>> thought the router was going bad, so rather than buy another hardware
>>>> router I converted an old PC into a router using IPCOP freeware - and
>>>> after all of the effort to build that box the same thing happened to
>>>> it as soon as we brought up VPC on a second box. The good news is
>>>> that now we have two good router/firewalls. :)
>>>>
>>>> To the questions:
>>>> - For anyone else running VPC concurrently on different real PCs in
>>>> the same network, how do you avoid this MAC address issue?
>>>> - Is there a better way to configure networking with VPC on the host
>>>> so that we still get access from guest to host/LAN/WAN?
>>>> - Might we be able to use one of the routers now to masquerade the MAC
>>>> of one of the boxes? (I'm not a networking guy so this is a shot in
>>>> the dark.) This isn't a real solution - what about those people who
>>>> run 50 VPCs in the same network?
>>>> - Looking at Settings for our VPC's I see the "Network" setting shows
>>>> the name of the real NIC, but the .VMC file shows the MAC Bridge
>>>> Miniport down in the ethernet_adapter node. There is only one
>>>> controller there. Is this a clue to a misconfiguration? We have
>>>> several VPC guests working this way.
>>>>
>>>> Thanks!
>>>
>>
>

RE: MAC Bridge Miniport, duplicate MACs on LAN

Sent: 10/11/2007
From: "Adisorn S."<(email address - cut out)>
Message:

Dear Mr.Gravano,
Not sure this is too late. but I have the same problem with you. I need to use loopback adapter with networkbridge for my Emulator. I hae used this for fix the problem -> just change your Loopback adapter MAC address at the settting>Networkconnection
rigth click at your Loopback->properties and then click the button configure

Next is click to tab "Advance" in the field of "Nextwork address". fill in the new MAC address... When your bridge the connection. Your Mac Bridge Miniport should get the difference MAC address,

Cheer,
Sang.

Posted via http://www.VirtualServerFaq.com - Brought to you by Business Information Technology Shop - http://www.bitshop.com

Show quoted text

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