Solved

Strange problem with NLB on Exchange FE servers

Posted on 2007-11-14
3
619 Views
Last Modified: 2013-11-30
Hi,
I have recently set up our 2 front-end and SMTP servers in an MS NLB. I gave the NLB cluster the same IP as our original mail server to avoid changing any MX records or A records for the OWA. Everything works fine except for a strange problem for which I can find no defined errors.

To test the cluster I am using telnet on the port for the SMTP service (25). This connects fine every time from outside our organisation, but for some reason the ability to connect in this method internally is distinctly sporadic.

Can anyone shed any light as to why this might be happening, or at least somewhere that I can look to find out the errors?

Additionally, I have run Ethereal on a number of clients whilst attempting the connection tothe cluster and it seems that the cluster simply does not respond to some clients internally, despite the fact that the same client can ping the cluster and connections from outside the organsiation work fine. Also, clients that can't connect at one time seem to just start working with no changes being made.
0
Comment
Question by:accidentexchange
3 Comments
 
LVL 8

Accepted Solution

by:
seeimred earned 500 total points
ID: 20286007
I think in our testing we found that Windows NLB would not work well for FE & SMTP farms. We use DNS RoundRobin entries for them instead.
0
 
LVL 1

Author Comment

by:accidentexchange
ID: 20287962
Thanks for the response. What I find strangest about this problem is that from outside our network, the load balance works perfectly, it is only when we try to connect from internal that the problem occurs.

I've increased the points available on this question as it is an urgent problem.
0
 
LVL 2

Expert Comment

by:Andrew_Wallbank
ID: 20610390
Do clients on your internal network pass through a router to get to the Mail server?  or is it on the same subnet?

Presumably the external device pass through a router/firewall?

it could be that the Internal devices are having trouble resolving the MAC address for the NLB (depending how it has been setup).  With traffic passing through a router/firewall these devices may be resolving them correctly.
0

Featured Post

How does your email signature look on mobiles?

Do your employees use mobile devices to reply to emails? With mobile becoming increasingly important to the business world, it is in your best interest to make sure that your email signature looks great across all types of devices.

Join & Write a Comment

Suggested Solutions

Not sure what the best email signature size is? Are you worried about email signature image size? Follow this best practice guide.
Learn to move / copy / export exchange contacts to iPhone without using any software. Also see the issues in configuration of exchange with iPhone to migrate contacts.
Familiarize people with the process of utilizing SQL Server views from within Microsoft Access. Microsoft Access is a very powerful client/server development tool. One of the SQL Server objects that you can interact with from within Microsoft Access…
To show how to create a transport rule in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Mail Flow >> Rules tab.:  To cr…

706 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now