Loopback as primary DNS

On 11/22/2009 1:37 AM, Dave Warren wrote:
> Wouldn't that effectively multihome the machine, and bring with it
> all those related hassles?

Yes, as I (mis)understand it, it does.

However I have never experienced any of the problems that others say
exist with multihomed DCs or boxen. (I'm not saying that they don't
exist, just that I've not run in to them.)



Grant. . . .

"Grant Taylor" <gtaylor@riverviewtech.net> wrote in message
news:hed34q$71a$2@tncsrv01.tnetconsulting.net...
> On 11/22/2009 1:37 AM, Dave Warren wrote:
>> Wouldn't that effectively multihome the machine, and bring with it all
>> those related hassles?
>
> Yes, as I (mis)understand it, it does.
>
> However I have never experienced any of the problems that others say exist
> with multihomed DCs or boxen. (I'm not saying that they don't exist, just
> that I've not run in to them.)
>
>
>
> Grant. . . .


In a single site, single subnet scenario, if setup right (outer NIC -
disable NetBIOS, DNS Interface only listen inside, NIC on bottom of binding
order, remove outer IP in Nameserver tab, etc, and even using the ISP on the
outer NIC to not register into DNS - but may generate 5782 or other
registration errors), you maybe be able to get away with it.

Ace

Ace

In message <#FPfUK4aKHA.2680@TK2MSFTNGP04.phx.gbl> "Ace Fekay [MCT]"
<aceman@mvps.RemoveThisPart.org> was claimed to have wrote:

>"Dave Warren" <dave-usenet@djwcomputers.com> wrote in message
>news:i75hg5tnm04tm75ivv586skiqmlbhece6k@4ax.com...
>> In message <he56a4$l8e$1@tncsrv01.tnetconsulting.net> Grant Taylor
>> <gtaylor@riverviewtech.net> was claimed to have wrote:
>>
>>>In the end I've found that having the Microsoft Loopback Adapter to be
>>>good for a number of different things. The fact that the DNS server
>>>will have an always up (unless I disable it) interface was a bonus.
>>
>> Wouldn't that effectively multihome the machine, and bring with it all
>> those related hassles?
>
>
>Good question. I actually don't remember, since I never use the loopback
>adapter. Logically, if you have the loopback adapter installed, it wants an
>IP, correct?

Yup. Think of it as a NIC connected to a switch without anything else
on the other end.

>So I would imagine yes, it would make it a multihomed machine.
>I don't have a test DC to test this with, and I am reluctant to install it
>on a production machine to test it.

I'd stick with that instinct :)

"Dave Warren" <dave-usenet@djwcomputers.com> wrote in message
news:ilmjg5hd4kojskpn342nrck82p058n0rff@4ax.com...
> In message <#FPfUK4aKHA.2680@TK2MSFTNGP04.phx.gbl> "Ace Fekay [MCT]"
> <aceman@mvps.RemoveThisPart.org> was claimed to have wrote:
>
>>"Dave Warren" <dave-usenet@djwcomputers.com> wrote in message
>>news:i75hg5tnm04tm75ivv586skiqmlbhece6k@4ax.com...
>>> In message <he56a4$l8e$1@tncsrv01.tnetconsulting.net> Grant Taylor
>>> <gtaylor@riverviewtech.net> was claimed to have wrote:
>>>
>>>>In the end I've found that having the Microsoft Loopback Adapter to be
>>>>good for a number of different things. The fact that the DNS server
>>>>will have an always up (unless I disable it) interface was a bonus.
>>>
>>> Wouldn't that effectively multihome the machine, and bring with it all
>>> those related hassles?
>>
>>
>>Good question. I actually don't remember, since I never use the loopback
>>adapter. Logically, if you have the loopback adapter installed, it wants
>>an
>>IP, correct?
>
> Yup. Think of it as a NIC connected to a switch without anything else
> on the other end.
>
>>So I would imagine yes, it would make it a multihomed machine.
>>I don't have a test DC to test this with, and I am reluctant to install it
>>on a production machine to test it.
>
> I'd stick with that instinct :)


As I thought! Thanks, Dave.

Ace

Wouldn't that effectively multihome the machine, and bring with it all those related hassles?



Yes, as I (mis)understand it, it does.



However I have never experienced any of the problems that others say exist with multihomed DCs or boxen.&nbsp; (I'm not saying that they don't exist, just that I've not run in to them.)



The algorithm for the NetLogon service (in very broad view) would be a simple three-stage affair:&nbsp; Find all of the network interfaces on the machine; find all of the IP addresses bound to each interface; send the DDNS Update requests to register them.&nbsp;



I would be quite surprised if there wasn't an exclusion, either of network interfaces that are marked as loopback interfaces (in the first stage) or of IP addresses in 127.0.0.0/8 (in the second stage), preventing the registration of IP addresses and network interfaces that are not routable outside of the machine itself.&nbsp; This is the sensible thing to do, and it would be surprising to learn that it wasn't being done.&nbsp; There's a relatively easy way and documented way to do perform this sort of exclusion using the SIO_ADDRESS_LIST_QUERY WinSock ioctl, which filters out machine-local and link-local IP addresses that are bound to software loopback network interfaces.




The existence of such a filter would explain why you've never had a problem, here.