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configuring multihomed server

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  #1  
Old 25-10-2007
runner7@fastmail.fm
 
Posts: n/a
configuring multihomed server

I would like to know if you need to have RRAS services installed and/
or a configured routing table if a Windows Server 2003
server is multihomed. Is it possible to just use 2 or more network
adapters on the
server without the server having to be configured as a router? Any
help or links to documents about this would be most appreciated.

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  #2  
Old 25-10-2007
Ace Fekay [MVP]
 
Posts: n/a
It all depends on what you need it for. Will it be routing between two
subnets? Then yes, you need RRAS. Will it be used as a NAT? Yes, you'll need
RRAS. Will it be a VPN server for outside clients to VPN into the sytem
with? Then yes, you need RRAS here too. And no, for a VPN server, you do not
need multiple NICs, but then again, it depends on what you need it for.

However, if this server is a domain controller, then you really really do
NOT want to multihome it. The additional NIC causes numerous issues if the
DC is not configured properly with the multiple NICs. I'm not trying to stop
you, but highly suggest not to. If you really want to, I do have a set of
instructions I can provide to assist you in properly configuring a
multihomed DC that involves a couple of reg changes, etc. Let me know if
this is the case.

However, if you want the multi NICs to increase network performance and laod
balancing, then you can install the appropriate NIC drivers from the
manufacturer and team them. This is good with a DC too.

I just saw your ost after asking pretty much the same question. I'm
interested in any information regarding configuring a multihomed DC for NAT
and to segment a network (two separate networks).

I really do not recommend it because the settings alter default DC
functionality inorder to make it work for what you want. It's better to get
a firewall like a Cisco PIX or similar to do the trick and let the DC do
it;s job.

Here's what I mean... happy reading...
===================

********************************
Multihomed DCs, DNS, RRAS servers.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
Below are the manual steps in more detail, which I had outlined in the above
paragraph:

Honestly, multi-homed DCs are not recommended because of the associated
issues that can occur, as you've encountered. We usually recommend
purchasing an inexpensive Linksys, DLink, etc, Cable/DSL router to perform
NAT for you, take out the extra NIC off the DC, but still let the DC handle
DHCP (and not the router).

Little background on AD and DNS:
First, just to get this out of the way, if you have your ISP's DNS addresses
in your IP configuration (DCs and clients), they need to be REMOVED.

If the ISP's DNS is in there, this will cause additional problems.

Also, AD registers certain records in DNS in the form of SRV records that
signify AD's resource and service locations. When there are multiple NICs,
each NIC registers. IF a client, or another DC queries DNS for this DC, it
may get the wrong record. One factor controlling this is Round Robin. If a
DC or client on another subnet that the DC is not configured on queries for
it, Round Robin will kick in offering one or the other. If the wrong one
gets offered, it may not have a route to it. On the other hand, Subnetmask
Priortization will ensure a querying client will get an IP that corresponds
to the subnet it's on, which will work. To insure everything works, stick
with one NIC.

Since this DC is multi-homed, it requires additional configuration to
prevent the public interface addresses from being registered in DNS. This
creates a problem for internal clients locating AD to authenticate and find
other services and resources such as the Global Catalog, file sharing and
the SYSVOL DFS share and can cause GPO errors with Userenv 1000 events to be
logged, authenticating to shares and printers, logging on takes forever,
among numerous other issues.

But if you like, there are some registry changes to eliminate the
registration of the external NIC. Here's the whole list of manual steps to
follow.

But believe me, it's much easier to just get a separate NAT device or
multihome a non-DC then having to alter the DC. - Good luck!

1. Insure that all the NICS only point to your internal DNS server(s) only
and none others, such as your ISP's DNS servers' IP addresses.

2. In Network & Dialup properties, Advanced Menu item, Advanced Settings,
move the internal NIC (the network that AD is on) to the top of the binding
order (top of the list).

3. Disable the ability for the outer NIC to register. The procedure, as
mentioned, involves identifying the outer NIC's GUID number. This link will
show you how:
246804 - How to Enable-Disable Windows 2000 Dynamic DNS Registrations (per
NIC too):
http://support.microsoft.com/?id=246804

4. Disable NetBIOS on the outside NIC. That is performed by choosing to
disable NetBIOS in IP Properties, Advanced, and you will find that under the
"WINS" tab. You may want to look at step #3 in the article to show you how
to disable NetBIOS on the RRAS interfaces if this is a RRAS server.
296379 - How to Disable NetBIOS on an Incoming Remote Access Interface
[Registry Entry]:
http://support.microsoft.com/?id=296379

Note: A standard Windows service, called the "Browser service", provides the
list of machines, workgroup and domain names that you see in "My Network
Places" (or the legacy term "Network Neighborhood"). The Browser service
relies on the NetBIOS service. One major requirement of NetBIOS service is a
machine can only have one name to one IP address. It's sort of a
fingerprint. You can't have two brothers named Darrell. A multihomed machine
will cause duplicate name errors on itself because Windows sees itself with
the same name in the Browse List (My Network Places), but with different
IPs. You can only have one, hence the error generated.

5. Disable the "File and Print Service" and disable the "MS Client Service"
on the outer NIC. That is done in NIC properties by unchecking the
respective service under the general properties page. If you need these
services on the outside NIC (which is unlikely), which allow other machines
to connect to your machine for accessing resource on your machine (shared
folders, printers, etc.), then you will probably need to keep them enabled.

6. Uncheck "Register this connection" under IP properties, Advanced
settings, "DNS" tab.

7. Delete the outer NIC IP address, disable Netlogon registration, and
manually create the required records

a. In DNS under the zone name, (your DNS domain name), delete the outer
NIC's IP references for the "LdapIpAddress". If this is a GC, you will need
to delete the GC IP record as well (the "GcIpAddress"). To do that, in the
DNS console, under the zone name, you will see the _msdcs folder. Under
that, you will see the _gc folder. To the right, you will see the IP address
referencing the GC address. That is called the GcIpAddress. Delete the IP
addresses referencing the outer NIC.

i. To stop these two records from registering that information,
use the steps provided in the links below:
Private Network Interfaces on a Domain Controller Are Registered in
DNShttp://support.microsoft.com/?id=295328

ii. The one section of the article that disables these records is
done with this registry entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters
(Create this Multi-String Value under it):
Registry value: DnsAvoidRegisterRecords
Data type: REG_MULTI_SZ
Values: LdapIpAddress
GcIpAddress

iii. Here is more information on these and other Netlogon Service records:
Restrict the DNS SRV resource records updated by the Netlogon service
[including GC]:
http://www.microsoft.com/technet/tre...o_rr_in_ad.asp

b. Then you will need to manually create these two records in DNS with
the IP addresses that you need for the DC. To create the

LdapIpAddress, create a new host under the domain, but leave the "hostname"
field blank, and provide the internal IP of the DC, which results in a
record that looks like:
(same as parent) A 192.168.5.200 (192.168.5.200 is used for illustrative
purposes)

i. You need to also manually create the GcIpAddress as well, if
this is a GC. That would be under the _msdcs._gc SRV record under the zone.
It is created in the same fashion as the LdapIpAddress mentioned above.

8. In the DNS console, right click the server name, choose properties, then
under the "Interfaces" tab, force it only to listen to the internal NIC's IP
address, and not the IP address of the outer NIC.

9. Since this is also a DNS server, the IPs from all NICs will register,
even if you tell it not to in the NIC properties. See this to show you how
to stop that behavior (this procedure is for Windows 2000, but will also
work for Windows 2003):
275554 - The Host's A Record Is Registered in DNS After You Choose Not to
Register the Connection's Address:
http://support.microsoft.com/?id=275554

10. If you haven't done so, configure a forwarder. You can use 4.2.2.2 if
not sure which DNS to forward to until you've got the DNS address of your
ISP.
How to set a forwarder? Good question. Depending on your operating
system,choose one of the following articles:

300202 - HOW TO: Configure DNS for Internet Access in Windows 2000
http://support.microsoft.com/?id=300202&FR=1

323380 - HOW TO: Configure DNS for Internet Access in Windows Server 2003
(How to configure a forwarder):
http://support.microsoft.com/d/id?=323380

Active Directory communication fails on multihomed domain controllers
http://support.microsoft.com/kb/272294

<==*** Some additional reading ***==>
More links to read up and understand what is going on:

292822 - Name Resolution and Connectivity Issues on Windows 2000 Domain
Controller with Routing and Remote Access and DNS Insta {DNS and RRAS and
unwanted IPs registering]:
http://support.microsoft.com/?id=292822

Active Directory communication fails on multihomed domain controllers
http://support.microsoft.com/kb/272294

246804 - How to enable or disable DNS updates in Windows 2000 and in Windows
Server 2003
http://support.microsoft.com/?id=246804

295328 - Private Network Interfaces on a Domain Controller Are Registered in
DNS
[also shows DnsAvoidRegisterRecords LdapIpAddress to avoid reg sameasparent
private IP]:
http://support.microsoft.com/?id=295328

306602 - How to Optimize the Location of a DC or GC That Resides Outside of
a Client's
Site [Includes info LdapIpAddress and GcIpAddress information and the SRV
mnemonic values]:
http://support.microsoft.com/?id=306602

825036 - Best practices for DNS client settings in Windows 2000 Server and
in Windows Server 2003 (including how-to configure a forwarder):
http://support.microsoft.com/default...b;en-us;825036

291382 - Frequently asked questions about Windows 2000 DNS and Windows
Server 2003 DNS
http://support.microsoft.com/?id=291382

296379 - How to Disable NetBIOS on an Incoming Remote Access Interface
[Registry Entry]:
http://support.microsoft.com/?id=296379

Rid Pool Errors and other mutlhomed DC errors, and how to configure a
multihomed DC, Ace Fekay, 24 Feb 2006
http://www.ureader.com/message/3244572.aspx
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  #3  
Old 26-10-2007
runner7@fastmail.fm
 
Posts: n/a
It definitely sounds like
multihoming a DC is not worth the hassle, but I would like to clarify
one point since I am relatively new to networking. It sounds like if
you are connecting two or more different networks or subnets with a
multihomed Windows server performing any role whatsoever, then that
server needs to have RRAS installed and be configured as a router. Is
this correct, or can you somehow connect two subnets with a dual-homed
server and not need routing installed?

Could either of you point out a link where I might get instructions
for setting up a workstation or server for routing using the method of
enabling routing in the registry? In particular, would I need to
manually configure a routing table?
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  #4  
Old 27-10-2007
Ace Fekay [MVP]
 
Posts: n/a
As long as it's not a DC, no worries. The problem with a DC and multi NICs
is multiple DNS registration. This the main concern, especially if RRAS
comes into the picture on a DC because now you have the RRAS IPs
registering. If a client is now looking for the DC (especially if it is a
GC), can it get to it from any of the IPs that may answer using Round Robin?
This is just the tip of what can go wrong. That's why it's basically not
worth the effort with a DC.

For what you are saying, multiple NICs on a member server, or a workstation,
as Bill points out, is fine.

How To Set Up Routing and Remote Access for an Intranet in Windows Server
2003 Enterprise Edition and Windows Server 2003 Standard Edition
http://support.microsoft.com/default...b;en-us;323415

Depending on your network, you may need to build a static route table,
unless the current routers are using a prototocol to broadcast is such as
OSPF or RIP, which Win2003 supports. How big of an infrastructure are we
talking about here? Is NAT involved? Lay out an example of what you are
trying to do. There are too many variables for a simple yes/no answer when
it comes to RRAS and routing.
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  #5  
Old 05-12-2007
Andrew Hayes
 
Posts: n/a
I don't know the OP's requirements, but from what has been said in this
thread, it looks like you could help me.

Currently, I have a single subnet (eg. 192.168.0.x) which I'll call LAN1,
and I wish to add 2 more subnets (eg. 192.168.1.x and 192.168.2.x) which I'll
call LAN2 and LAN3.

This is to allow me to setup a staging environment that duplicates the real
environment (where LAN1, LAN2 and LAN3 make a WAN through IP-VPN).

From what I've read of routing, all I need is a desktop if I want to use IP
Routing only, although I'd rather use RRAS so I can simulate the dial-in VPN
users as well at a later stage.

To accomplish this I would need a server with 3 NIC's. Each one has a fixed
IP for each of the 3 subnets (NIC-LAN1, NIC-LAN2, NIC-LAN3 for examples sake).

Up to this point I think I understand it.

The next part is configuring RRAS so that a desktop in LAN1 can use TS to
connect to a server in LAN2 or LAN3, and that a server in LAN2 or LAN3 can
use TS to connect to a server in LAN3 or LAN2, respectively.

Could one of you networking boffs explain how I need to setup the RRAS?
Either using a wizard, or manually.

Just to clarify the settings, here is what I did (feel free to skip to the
end as I've included most of the steps for the benefit of others).

I run Adminsitrative Tools | Routing and Remote Access tool, then I
right-click on my SERVER, and choose the "Configure and Enable Routing and
Remote Access..." which brings up the "Windows Firewall/Internet Connection
Sharing service is enabled for SERVER..." message.

Closed that dialog, then went to Adminstrative Tools | Services tool and
stopped the "Windows Firewall/Internet Connection Sharing (ICS)" service,
then went to the service Properties and set it's "Startup type" to Disabled.

Go back to Routing and Remote Access and choose Configure and Enable again.
Up pops the RRAS setup wizard.

Selected "Custom configuration" and hit Next, choose "LAN Routing" only and
hit Next, then Finish. When it asks me if I want to start the service, I
click Yes.

In the tree, under Network Connections, I see Loopback, LAN1, LAN2, LAN3 and
Internal. All Connected and all Enabled.

Under IP Routing | General, I see Loopback (127.0.0.1, Up), LAN1
(192.168.0.1, Up), LAN2 (192.168.1.1, Up), LAN3 (192.168.2.1, Up) and
Internal (Not available, Unknown).

IPCONFIG looks like this:

Windows IP Configuration

Ethernet adapter LAN1:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.0.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :

Ethernet adapter LAN2:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.1.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :

Ethernet adapter LAN3:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 192.168.2.1
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :

Is that all I need to do, or do I need to setup Static Routes?

This is the one that caused me a few problems, which I have resolved, but I
am including the details so that others may glean some insight.

We also have another LAN on a different WAN (for arguments sake we'll call
it LANX - 192.168.3.x), and most machines on LAN1 use the H/W router
(192.168.0.100 -> Leased Line -> 192.168.3.100) to LANX as the default
gateway, as LANX is a data center that contains the corporate servers (shared
folders, email, etc.).

However, the LAN2 and LAN3 machines have no need to connect to LANX, hence
why I didn't include it in RRAS.

Anyhow. The offshoot of this was that the desktops on LAN1 that need access
to LANX, as well as the staging servers in LAN2 and LAN3, had to have their
Default Gateway removed and then persistant static routes added to their
routing tables in order to access resources on both LAN1 and LANX.

ROUTE ADD 192.168.0.0 MASK 255.255.255.0 192.168.0.1 -P
ROUTE ADD 192.168.3.0 MASK 255.255.255.0 192.168.0.100 -P

Once that was all done everything was hunky dory. However, I do not know if
this is the best way to go about it. I just know it works. Any further
comments?

A little tool to help check line width.
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  #6  
Old 07-12-2007
Bill Grant
 
Posts: n/a
In theory you do not need RRAS. You do not even need a server OS. You can
use a workstation as a router by putting two NICs in it, connecting them to
two different networks and enabling IP routing in the registry.

RRAS is a pretty complete router and remote access server and it has
builtin wizards to configure it for most common tasks. If you configure it
as a LAN router only, it just enables IP routing.

Enabling IP routing allows the machine to forward traffic arriving on
one interface to be sent on through the other interface. The simplest case
is a setup like this.

192.168.1.x dg 192.168.1.254
|
192.168.1.254 dg blank
router
192.168.21.254 dg blank
|
192.168.21.x dg 192.168.21.254

Machines in either subnet can communicate directly "on the wire"
using hardware addressing. Traffic for a machine in the "other" subnet will
be sent to the default router (because it is not in the local subnet). If IP
routing is enabled, the router can deliver this traffic directly in the
"other" subnet from its other NIC.

No, you do not need to configure anything in the routing table. A machine
will automatically set up a route to handle the subnets used by the NICs
attached to the router. All you need to do is enable IP routing in the
registry. If the machines on each side of the router use the router as their
default gateway, everyting just works.

Here is the KB explaining how to enable IP routing in XP.

http://support.microsoft.com/kb/315236

It certainly isn't a very elegant solution. I don't like the idea of
putting static routes on workstations. It is better to configure your
network so that the routers actually do the routing.
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  #7  
Old 23-06-2010
Member
 
Join Date: Jun 2010
Posts: 1
Re: configuring multihomed server

I needed to configure my two DC's (which already had back-end nic's installed but weren't connected to anything) to talk to my new SAN. First attempt failed as I forgot about the preliminary steps needed to prevent them from causing havoc with AD and DNS. So I had a little havoc going on.

Your info was helpful but ultimately I followed the steps outlined here to configure the NIC's and simply scoured my DNS (based on your info) which was already configured to listen on specific interfaces, for any references to the back-end nics and all is fine.

I now have two multihomed DC's talking to my SAN (via the storage LAN) and User LAN without issues.

I also want to say that there are times when a multihomed DC is unavoidable, such as in my case where I inherited a network with a DC running Exchange which is low on drive space. Ultimately it is easier to configure a set of back-end NICS and connect it to the SAN and move the Store rather than stand up another server and move the Exchange installation. I am currently in the process of virtualizing and will correct these faux pas' as I go but I gotta keep the hamsters runnin' for now.
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