SP1 NLB Hub Transport (Full Version)

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RMGreenley -> SP1 NLB Hub Transport (7.Dec.2007 12:02:15 PM)

Okay, so SP1 gives us the ability to NLB our HT servers.  Unfortunately, I haven't found much in the way of documentation on how to do it.  Anyone out there know?

Thanks!

Ray G.



Henrik Walther -> RE: SP1 NLB Hub Transport (7.Dec.2007 12:34:49 PM)

Well there's typically no reason why you would NLB your HT servers, but I guess you mean have the HT role on same severs as the CAS in a NLB? Yes with SP1 this is now a supported scenario and I know there's a few lines about it in the E2K7 documentation too, but I can find it right now. I have the link to this piece of information in a mail, I'll dig it up later.



RMGreenley -> RE: SP1 NLB Hub Transport (7.Dec.2007 12:39:37 PM)

Thanks Henrik.  Actually, there seems to me to be a very good reason to NLB the HT servers.  We have internal applications and scanners that send messages through the Exchange server via SMTP.  Without being able to use the NLB address, I'd have to specifically specify one HT server or the other in order for those SMTP messages to go through.  If that server were to go down, the applications/scanners would be stuck.  If I can use the NLB address, they should keep functioning.

Do you know of a better way to handle this situation?  Using NLB with the HT servers seems to be the most natural solution to me, but I'm not an Exchange expert.

Thanks again!

Ray G.



Henrik Walther -> RE: SP1 NLB Hub Transport (7.Dec.2007 2:35:12 PM)

Here's the info (in the very bottom of the page):
http://technet.microsoft.com/en-us/library/bb124398.aspx

HT servers have built-in resiliency meaning that if one is down, the second in the AD site will be asked.



RMGreenley -> RE: SP1 NLB Hub Transport (7.Dec.2007 3:19:52 PM)

Thanks for the link, Henrik.

HT servers may have 'built-in resiliency' for some situations, but it doesn't apply when you're trying to send an message via SMTP.  I tested it out with one of our apps where I had it send a message via SMTP through one of the HT servers.  It worked fine and I got the message.  Then I disabled the public NIC on the server and tried to send it again.  This time it failed to find the server.  When I re-enabled the NIC, it started working again.

I had seen that article before.  At the bottom it states that NLB is now supported and can be used for situations like the one we are in:

"Load balancing of inbound SMTP connections for applications that submit e-mail to the Exchange organization."

However, it doesn't say how to set it up.  It doesn't happen automagically, so there's obviously somewhere that it needs to be configured.  But where?  I haven't found any specific documentation on the subject, and I'm reluctant to try random things and hope that it works.

Ray G.



Henrik Walther -> RE: SP1 NLB Hub Transport (7.Dec.2007 3:57:58 PM)

Ray,

Yes if your applications doesn't allow you to specify multiple SMTP servers, I can see your problem.

You configure HT servers in a NLB in a similar way as you do with CAS. Did you see my three part article series on Configuring CAS in an NLB here on the site?



RMGreenley -> RE: SP1 NLB Hub Transport (7.Dec.2007 4:09:08 PM)

Yeah, that article is the only way I was able to get my HT/CAS servers up in the first place (thanks, by the way!)  It looks like the only 'variable' part of the setup would be to add the SMTP ports to the Port Rules list.  I did go in and add ports 25 and 465 TCP with the same configuration as the other ports (Multiple Host/Affinity Single), and it still didn't work.  Maybe I didn't get all that I needed or the right ones?  Do I need UDP as well? I can give it a shot.

Ray G.



RMGreenley -> RE: SP1 NLB Hub Transport (13.Dec.2007 9:27:17 AM)

Any other throughts on this?  I've looked into it more and I still can't find anything helpful in getting the NLB HT set up.

Thanks.

Ray G.



Henrik Walther -> RE: SP1 NLB Hub Transport (13.Dec.2007 3:03:57 PM)

Well HT servers are really configured similar to CAS when it comes to NLB, you just specify other TCP ports.

I must do further test on this feature before I can come with additional details (actually I'm currently writing an article on this topic).

Things you can test:

- Start by testing the feature using simple telnet sessions instead of with your app
- Can you telnet to port 25 when you shutdown one node?



RMGreenley -> RE: SP1 NLB Hub Transport (19.Dec.2007 10:59:12 AM)

Henrik,

Thanks a lot for your help.  I'm looking forward to your article.  Have you gotten it to work at all?  I've still had no luck.

Using telnet, I can access each individual server, but I cannot connect using the NLB DNS name.  After successfully telneting into port 25 on the first server, if I try to disable that server (by disabling both the public and private network connections), I cannot successfully telnet in using that DNS name any longer (so it doesn't know to fail over to the other HT server on its own).

Thanks again.

Ray G.



RMGreenley -> RE: SP1 NLB Hub Transport (2.Jan.2008 3:51:46 PM)

Henrik,

Any tips you can give me in advance of the article?  I'm still stuck on getting this to work.

Thanks.

Ray G.



boomvader -> RE: SP1 NLB Hub Transport (3.Jan.2008 5:30:42 PM)

I am also interested in this article, Henrik.  I have architected the same configuration and hope that it will work as planned.  Thanks!

-boom

quote:

ORIGINAL: RMGreenley

Henrik,

Any tips you can give me in advance of the article?  I'm still stuck on getting this to work.

Thanks.

Ray G.



garconer -> RE: SP1 NLB Hub Transport (4.Jan.2008 8:30:23 AM)

People,
 
There is no easy way to get fault tolerance inside HT for port TCP 25 for applications other then Exchange 2007. You do can use NLB for balancing TCP 25, but it's not supporteb by M$.
 
If you use clients such Outlook Express, configure them to use TCP 587 for SMTP and enable NLB on this port at HT servers. Notice that, by default, there is a receive connector on every HT listening on this port named "Client <server name>". For other applications, get a read at their documentation to find out if it's possible to change SMTP port.
 
If you have a scenario with thousand of OE already configured to use default SMTP port TCP 25 or your apps only supports TCP 25 for SMTP, and want to achieve some fault tolerance, these are my recommendations:
 
1. Use NLB for TCP 25 despite of M$ saying it's not supported. EX2K7 does not "see" NLB acting. It's pretty straightforward, it works (I'm using it to provide SMTP for more than 1.500 Outlook Express users), and it is transparent to Exchange 2007 Routing engine.
 
2. Use DNS roud robin (notice that you might come up with some errors)
 
I'd go with #1 option.
 
Rodrigo Garcone



RMGreenley -> RE: SP1 NLB Hub Transport (4.Jan.2008 8:34:57 AM)

garconer,

Are you sure it's not supported? Here's some text from Microsoft Technet that leads me to believe that what I'm looking for should be possible
(http://technet.microsoft.com/en-us/library/bb124398.aspx):

"New in Exchange 2007 Service Pack 1
Exchange 2007 Service Pack 1 (SP1) supports the use of Network Load Balancing (NLB) to achieve high availability for specific types of connections to the Hub Transport server role. NLB can be used to provide high availability in the following scenarios:

Load balancing of inbound SMTP connections for POP and IMAP client connections to the default Receive connector named "Client <Server Name>" that is created only on Hub Transport servers.

Load balancing of inbound SMTP connections for applications that submit e-mail to the Exchange organization."

It's that second scenario that I'm personally most interested in but I haven't been able to figure out how to do it (or I'm just doing something wrong).  I've enabled port 25 for the NLB cluster, but it still won't accept SMTP connections for me.  I'm obviously missing something, but I don't know what.

Ray G.



Henrik Walther -> RE: SP1 NLB Hub Transport (4.Jan.2008 8:52:15 AM)

Load balancing Hub Transport servers using NLB technology is fully supported by MS when using Exchange 2007 SP1. However only for inbound client connections and inbound SMTP connections (such as from LOB applications, SharePoint etc.). Using NLB intra-org (between HT severs internally in the organizations)´is however not supported.

BTW I got it fully working and have almost finisehd the mentioned article. One thing I observed during my testing was that I only could get it working using Multicast mode on the NLB NIC.



RMGreenley -> RE: SP1 NLB Hub Transport (4.Jan.2008 8:53:38 AM)

Henrik,

GREAT!  Thanks a lot!  I'm really looking forward to the article.

Ray G.



garconer -> RE: SP1 NLB Hub Transport (4.Jan.2008 9:13:06 AM)

I'm not 100% sure it's not supported, but M$ says "NLB should not be used to distribute connections for internal routing between Hub Transport servers".
 
Anyway, I'm running the second scenario without any issue. Your problem might be with permissions on the connector, since I'm assuming that your NLB configuration is done correctly (if it's not the case, configure TCP 25 as you did for POP and IMAP)
 
Go to EMC > Server Configuration > Hub Transport. For each HT Server, open properties of Default <server name> connection and then Authentication Tab. Enable Basic Authentication and uncheck "offer basic authentication only after...". Under Permission, make sure Exchange Users and Anonymous is selected. Only select anonymous if you cannot authenticate smtp connections. In my case, all Outlook Express users has smtp authentication configured, so I haven't enabled anonymous access.
 
Get a read at http://www.exchangeninjas.com/TUPMPermissions. It migt help you.
 
 
 



Henrik Walther -> RE: SP1 NLB Hub Transport (4.Jan.2008 9:22:59 AM)

quote:

ORIGINAL: garconer

I'm not 100% sure it's not supported, but M$ says "NLB should not be used to distribute connections for internal routing between Hub Transport servers". 
 


Correct! MS doesn't support NLB for intra-org purposes, that is between HT servers in the org.



garconer -> RE: SP1 NLB Hub Transport (4.Jan.2008 9:44:35 AM)

Henrik,
 
It's been working for me with Unicast and 2 NICs.
 
Could you please explain me what you would mentioned with "Using NLB intra-org (between HT severs internally in the organizations)´is however not supported." ?

Tks
 
Rodrigo Garcone



RMGreenley -> RE: SP1 NLB Hub Transport (4.Jan.2008 9:51:02 AM)

quote:

ORIGINAL: garconer

Go to EMC > Server Configuration > Hub Transport. For each HT Server, open properties of Default <server name> connection and then Authentication Tab. Enable Basic Authentication and uncheck "offer basic authentication only after...". Under Permission, make sure Exchange Users and Anonymous is selected. Only select anonymous if you cannot authenticate smtp connections. In my case, all Outlook Express users has smtp authentication configured, so I haven't enabled anonymous access.
 
Get a read at http://www.exchangeninjas.com/TUPMPermissions. It migt help you.

garconer,

Thanks for the suggestions.  I tried adjusting the HT Default receive connectors as you mentioned, but I still haven't had luck connecting to the NLB cluster over port 25.  In the NLB Port Rules, I added port 25 for all cluster addresses and Both protocols.  I set the Flitering Mode to Multiple Host with Affinity set to Single.  Does that sound right?  I'll check out the link you gave as well.

Thanks,
Ray G.



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