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Backup network cards not working as expected (metric?)

 
 
Nick Gilbert
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      06-21-2007, 03:59 PM
Hi,

Can a computer have two cards in the same machine which can both work at
the same time on the same subnet? (for the purposes of redundancy)

The situation is this:

I have three servers, each with two network cards:

SERVER 1
10.10.250.200 primary
10.10.250.205 backup

SERVER 2
10.10.250.206 primary
10.10.250.207 backup

[etc]

The problem is, with the default settings, the machines cannot see each
other on the their primary network cards (not even with ping).

For some reason, the backup card actually seems to be the default. If I
disable BOTH backup cards, they can see each other fine.

They can also see each other fine if force the primary NIC to have a
lower metric than the backup card. HOWEVER as soon as I do this, the
machines can no longer be accessed on their backup cards.

Is there no way to configure the machines such that both cards can work
at the same time so that in the event one card fails or is unplugged,
the second card will still work?

On ONE of my machines in the same rack, this setup is working fine and I
can get to the machine on both of it's network cards.

Nick...


 
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Anthony
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      06-21-2007, 04:54 PM
Nick,
Teaming the cards is the solution to this. You need the vendor's utility to
do it,
Anthony
http://www.airdesk.co.uk


"Nick Gilbert" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi,
>
> Can a computer have two cards in the same machine which can both work at
> the same time on the same subnet? (for the purposes of redundancy)
>
> The situation is this:
>
> I have three servers, each with two network cards:
>
> SERVER 1
> 10.10.250.200 primary
> 10.10.250.205 backup
>
> SERVER 2
> 10.10.250.206 primary
> 10.10.250.207 backup
>
> [etc]
>
> The problem is, with the default settings, the machines cannot see each
> other on the their primary network cards (not even with ping).
>
> For some reason, the backup card actually seems to be the default. If I
> disable BOTH backup cards, they can see each other fine.
>
> They can also see each other fine if force the primary NIC to have a lower
> metric than the backup card. HOWEVER as soon as I do this, the machines
> can no longer be accessed on their backup cards.
>
> Is there no way to configure the machines such that both cards can work at
> the same time so that in the event one card fails or is unplugged, the
> second card will still work?
>
> On ONE of my machines in the same rack, this setup is working fine and I
> can get to the machine on both of it's network cards.
>
> Nick...
>
>



 
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Nick Gilbert
Guest
Posts: n/a

 
      06-22-2007, 09:48 AM
Thanks, it seems my networks cards do support this, but I'm reluctant to
configure this setup now that the server is at a remote location.

It's really weird because previously I've always just given the second
adapter a different IP address and both cards have worked fine. Perhaps
something has changed in Windows 2003 Server?

Nick...

Anthony wrote:
> Nick,
> Teaming the cards is the solution to this. You need the vendor's utility to
> do it,
> Anthony
> http://www.airdesk.co.uk
>
>
> "Nick Gilbert" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Hi,
>>
>> Can a computer have two cards in the same machine which can both work at
>> the same time on the same subnet? (for the purposes of redundancy)
>>
>> The situation is this:
>>
>> I have three servers, each with two network cards:
>>
>> SERVER 1
>> 10.10.250.200 primary
>> 10.10.250.205 backup
>>
>> SERVER 2
>> 10.10.250.206 primary
>> 10.10.250.207 backup
>>
>> [etc]
>>
>> The problem is, with the default settings, the machines cannot see each
>> other on the their primary network cards (not even with ping).
>>
>> For some reason, the backup card actually seems to be the default. If I
>> disable BOTH backup cards, they can see each other fine.
>>
>> They can also see each other fine if force the primary NIC to have a lower
>> metric than the backup card. HOWEVER as soon as I do this, the machines
>> can no longer be accessed on their backup cards.
>>
>> Is there no way to configure the machines such that both cards can work at
>> the same time so that in the event one card fails or is unplugged, the
>> second card will still work?
>>
>> On ONE of my machines in the same rack, this setup is working fine and I
>> can get to the machine on both of it's network cards.
>>
>> Nick...
>>
>>

>
>

 
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Anthony
Guest
Posts: n/a

 
      06-22-2007, 12:06 PM
I agree, you can't set this up remotely.
I am not an expert on the inner workings of network drivers, so maybe
someone else can respond, but I think the crucial point is the binding order
of the drivers. You can run more than one IP address one one card, but you
will see that outbound packets go out on the lowest IP address. This is all
handled by the driver. If you run multiple cards on the same subnet, the
packet can come in on one card but be sent out on another, so the same
driver is not handling them. It can work, but not reliably. Teaming is a
form of Uber-driver that provides one logical management of packets across
more than one driver. If you run the two cards on separate subnets the
problem does not arise because packets are confined to one subnet on one
card. This is a non-technical explanation based on observation, so you may
get a better reply from a specialist. However I am pretty sure the MS
documentation says don't run two cards on the same network.
As the server is remote, and if you have a switch at the other end, you
could set up a second VLAN and attach the second card to that, giving you
two ways of getting to the server if one card fails. But teaming is the real
answer for resilience.
Anthony
http://www.airdesk.co.uk




"Nick Gilbert" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Thanks, it seems my networks cards do support this, but I'm reluctant to
> configure this setup now that the server is at a remote location.
>
> It's really weird because previously I've always just given the second
> adapter a different IP address and both cards have worked fine. Perhaps
> something has changed in Windows 2003 Server?
>
> Nick...
>
> Anthony wrote:
>> Nick,
>> Teaming the cards is the solution to this. You need the vendor's utility
>> to do it,
>> Anthony
>> http://www.airdesk.co.uk
>>
>>
>> "Nick Gilbert" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> Hi,
>>>
>>> Can a computer have two cards in the same machine which can both work at
>>> the same time on the same subnet? (for the purposes of redundancy)
>>>
>>> The situation is this:
>>>
>>> I have three servers, each with two network cards:
>>>
>>> SERVER 1
>>> 10.10.250.200 primary
>>> 10.10.250.205 backup
>>>
>>> SERVER 2
>>> 10.10.250.206 primary
>>> 10.10.250.207 backup
>>>
>>> [etc]
>>>
>>> The problem is, with the default settings, the machines cannot see each
>>> other on the their primary network cards (not even with ping).
>>>
>>> For some reason, the backup card actually seems to be the default. If I
>>> disable BOTH backup cards, they can see each other fine.
>>>
>>> They can also see each other fine if force the primary NIC to have a
>>> lower metric than the backup card. HOWEVER as soon as I do this, the
>>> machines can no longer be accessed on their backup cards.
>>>
>>> Is there no way to configure the machines such that both cards can work
>>> at the same time so that in the event one card fails or is unplugged,
>>> the second card will still work?
>>>
>>> On ONE of my machines in the same rack, this setup is working fine and I
>>> can get to the machine on both of it's network cards.
>>>
>>> Nick...
>>>
>>>

>>


 
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