No ping between NLB cluster with two NICs

Hi People,

I've got a Windows 2003 R2 SP2 (all patched up) pair of machines in an NLB
cluster.

Each machine has two NICs.

The first NIC has a static IP, which is mapped in DNS, this NIC also has a
default route.

The second NIC has a static (dedicated) IP, which isn't in DNS, the NLB IP
(which is in DNS) and no default route (this is how the NLB admin tool set it
up).

My problem is that the two servers can't communicate with each other. They
can't ping, file share, web, nothing.

The NLB IP is only for TCP port 80 and is configured for Unicast, since I
shouldn't need multicast (and the problems that come with) with two NICs.

Any one got any ideas?

Soon'ish
Craig


--
Craig dot Humphrey at ChapmanTripp dot com

Have you tried changing the binding order so that the non-NLB NIC is at the
top? This is the only thing that occurs to me at the moment. The fact of no
DG on the NLB NICs and no DNS registration of their IPs wouldn't make a
difference when attempting to communicate to each other on the same subnet.
I imagine the traffic would go like this:

Machine1 want to communicate with Machine2, both have NIC1, no DG, no DNS
servers, not registered in DNS and NIC2, DG and DNS servers configured and
registered in DNS.
Machine1 needs an IP address and so uses its NIC with a configured DNS
server to get to the DNS server and gets the IP of the target machine.
Machine1 compares the IP address of Machine2 with its own and works out they
are on the same subnet, so no need to route to the DG, just send direct.
It has the choice of which NIC to use to communicate with and has to pick
somehow and I figure it would use the one highest up in the binding order.

This is just a guess, but I have been thinking about this lately since I
will be setting up a dual NIC NLB cluster soon and was wondering how this
would work.

Please let me know if this works,

Cheers,
Jeremy

"Craig Humphrey" <(E-Mail Removed)> wrote in message
news:E7A8C49B-6276-444A-8595-(E-Mail Removed)...
> Hi People,
>
> I've got a Windows 2003 R2 SP2 (all patched up) pair of machines in an NLB
> cluster.
>
> Each machine has two NICs.
>
> The first NIC has a static IP, which is mapped in DNS, this NIC also has a
> default route.
>
> The second NIC has a static (dedicated) IP, which isn't in DNS, the NLB IP
> (which is in DNS) and no default route (this is how the NLB admin tool set
> it
> up).
>
> My problem is that the two servers can't communicate with each other.
> They
> can't ping, file share, web, nothing.
>
> The NLB IP is only for TCP port 80 and is configured for Unicast, since I
> shouldn't need multicast (and the problems that come with) with two NICs.
>
> Any one got any ideas?
>
> Soon'ish
> Craig
>
>
> --
> Craig dot Humphrey at ChapmanTripp dot com

On the same segment and in the same IP subnet the machines do communicate
directly using hardware (MAC) addresses of the NICs. If the sending machine
does not know the MAC address of the target it sends an ARP request on the
wire. When it gets the MAC address it can send directly on the wire using
the NIC's MAC address.

"Jeremy" <(E-Mail Removed)> wrote in message
news:3077BBF6-D56A-4489-8889-(E-Mail Removed)...
> Have you tried changing the binding order so that the non-NLB NIC is at
> the top? This is the only thing that occurs to me at the moment. The fact
> of no DG on the NLB NICs and no DNS registration of their IPs wouldn't
> make a difference when attempting to communicate to each other on the same
> subnet. I imagine the traffic would go like this:
>
> Machine1 want to communicate with Machine2, both have NIC1, no DG, no DNS
> servers, not registered in DNS and NIC2, DG and DNS servers configured and
> registered in DNS.
> Machine1 needs an IP address and so uses its NIC with a configured DNS
> server to get to the DNS server and gets the IP of the target machine.
> Machine1 compares the IP address of Machine2 with its own and works out
> they are on the same subnet, so no need to route to the DG, just send
> direct.
> It has the choice of which NIC to use to communicate with and has to pick
> somehow and I figure it would use the one highest up in the binding order.
>
> This is just a guess, but I have been thinking about this lately since I
> will be setting up a dual NIC NLB cluster soon and was wondering how this
> would work.
>
> Please let me know if this works,
>
> Cheers,
> Jeremy
>
> "Craig Humphrey" <(E-Mail Removed)> wrote in
> message news:E7A8C49B-6276-444A-8595-(E-Mail Removed)...
>> Hi People,
>>
>> I've got a Windows 2003 R2 SP2 (all patched up) pair of machines in an
>> NLB
>> cluster.
>>
>> Each machine has two NICs.
>>
>> The first NIC has a static IP, which is mapped in DNS, this NIC also has
>> a
>> default route.
>>
>> The second NIC has a static (dedicated) IP, which isn't in DNS, the NLB
>> IP
>> (which is in DNS) and no default route (this is how the NLB admin tool
>> set it
>> up).
>>
>> My problem is that the two servers can't communicate with each other.
>> They
>> can't ping, file share, web, nothing.
>>
>> The NLB IP is only for TCP port 80 and is configured for Unicast, since I
>> shouldn't need multicast (and the problems that come with) with two NICs.
>>
>> Any one got any ideas?
>>
>> Soon'ish
>> Craig
>>
>>
>> --
>> Craig dot Humphrey at ChapmanTripp dot com
>

Hi Guys,

thanks for your responses.

Turns out, that even with Server 2003 R2 SP2, and dual NICs, if you want
machines in the NLB cluster to communicate (outside of their NLB heartbeat),
then you still need to follow the instructions in:
http://technet2.microsoft.com/window...855cb1033.mspx

I had thought that this only ever applied to single NIC machines.

Apparently not.

Just a word of warning. Once you follow those instructions, the machines in
the NLB cluster will only be able to communicate with each other on their NLB
NIC dedicated IPs. So I had to put entries in the HOSTS file, to make sure
that the machines involved resolved the right IPs.

These are some interesting gotch-ya's for young players!

Later'ish
Craig

--
Craig dot Humphrey at ChapmanTripp dot com


"Bill Grant" wrote:

> On the same segment and in the same IP subnet the machines do communicate
> directly using hardware (MAC) addresses of the NICs. If the sending machine
> does not know the MAC address of the target it sends an ARP request on the
> wire. When it gets the MAC address it can send directly on the wire using
> the NIC's MAC address.
>
> "Jeremy" <(E-Mail Removed)> wrote in message
> news:3077BBF6-D56A-4489-8889-(E-Mail Removed)...
> > Have you tried changing the binding order so that the non-NLB NIC is at
> > the top? This is the only thing that occurs to me at the moment. The fact
> > of no DG on the NLB NICs and no DNS registration of their IPs wouldn't
> > make a difference when attempting to communicate to each other on the same
> > subnet. I imagine the traffic would go like this:
> >
> > Machine1 want to communicate with Machine2, both have NIC1, no DG, no DNS
> > servers, not registered in DNS and NIC2, DG and DNS servers configured and
> > registered in DNS.
> > Machine1 needs an IP address and so uses its NIC with a configured DNS
> > server to get to the DNS server and gets the IP of the target machine.
> > Machine1 compares the IP address of Machine2 with its own and works out
> > they are on the same subnet, so no need to route to the DG, just send
> > direct.
> > It has the choice of which NIC to use to communicate with and has to pick
> > somehow and I figure it would use the one highest up in the binding order.
> >
> > This is just a guess, but I have been thinking about this lately since I
> > will be setting up a dual NIC NLB cluster soon and was wondering how this
> > would work.
> >
> > Please let me know if this works,
> >
> > Cheers,
> > Jeremy

This is true... There are some things you can do with Proxy ARP and such
that you can do on your directly attached switches to get around some of
this, but most people don't really have a need to go into all that. By the
time that your environment is sophisticated to use it, you are probably
buying F5s and the like making it moot.
--
Ryan Hanisco
MCSE, MCTS: SQL 2005, Project+
Chicago, IL

Remember: Marking helpful answers helps everyone find the info they need
quickly.


"Craig Humphrey" wrote:

> Hi Guys,
>
> thanks for your responses.
>
> Turns out, that even with Server 2003 R2 SP2, and dual NICs, if you want
> machines in the NLB cluster to communicate (outside of their NLB heartbeat),
> then you still need to follow the instructions in:
> http://technet2.microsoft.com/window...855cb1033.mspx
>
> I had thought that this only ever applied to single NIC machines.
>
> Apparently not.
>
> Just a word of warning. Once you follow those instructions, the machines in
> the NLB cluster will only be able to communicate with each other on their NLB
> NIC dedicated IPs. So I had to put entries in the HOSTS file, to make sure
> that the machines involved resolved the right IPs.
>
> These are some interesting gotch-ya's for young players!
>
> Later'ish
> Craig
>
> --
> Craig dot Humphrey at ChapmanTripp dot com
>
>
> "Bill Grant" wrote:
>
> > On the same segment and in the same IP subnet the machines do communicate
> > directly using hardware (MAC) addresses of the NICs. If the sending machine
> > does not know the MAC address of the target it sends an ARP request on the
> > wire. When it gets the MAC address it can send directly on the wire using
> > the NIC's MAC address.
> >
> > "Jeremy" <(E-Mail Removed)> wrote in message
> > news:3077BBF6-D56A-4489-8889-(E-Mail Removed)...
> > > Have you tried changing the binding order so that the non-NLB NIC is at
> > > the top? This is the only thing that occurs to me at the moment. The fact
> > > of no DG on the NLB NICs and no DNS registration of their IPs wouldn't
> > > make a difference when attempting to communicate to each other on the same
> > > subnet. I imagine the traffic would go like this:
> > >
> > > Machine1 want to communicate with Machine2, both have NIC1, no DG, no DNS
> > > servers, not registered in DNS and NIC2, DG and DNS servers configured and
> > > registered in DNS.
> > > Machine1 needs an IP address and so uses its NIC with a configured DNS
> > > server to get to the DNS server and gets the IP of the target machine.
> > > Machine1 compares the IP address of Machine2 with its own and works out
> > > they are on the same subnet, so no need to route to the DG, just send
> > > direct.
> > > It has the choice of which NIC to use to communicate with and has to pick
> > > somehow and I figure it would use the one highest up in the binding order.
> > >
> > > This is just a guess, but I have been thinking about this lately since I
> > > will be setting up a dual NIC NLB cluster soon and was wondering how this
> > > would work.
> > >
> > > Please let me know if this works,
> > >
> > > Cheers,
> > > Jeremy
>