Is there any way I can force one of our Exchange Edge Transport Servers to send SMTP traffic outbound through a specific ISA Server when the ISA server is an an NLB cluster?
I've changed the default gateway on the Edge Transport Server in question to be the IP address of the Specific ISA server I want SMTP to be sent out through, but it still seems to be sending SMTP traffic outbound across all the servers in ISA array.
Apologies if this is a dumb question, but I'm relatively new to ISA.
Yes, I've set the SMTP server's default gateway to be the DIP of the ISA server I want to force SMTP traffic through, but when the SMTP server sends SMTP traffic it's still going out through the other server in the array (according to the ISA logs and the fact that some e-mail is failing the rDNS lookup due to the physical IP address being stamped with the external IP of the 'other' ISA server).
Is there a chance it is actually hitting the right ISA server internally, but then NLB is routing out through the external adapter of the other ISA server? Can this happen?
No, it's the primary IP as set on the external adapter. Should it be tagged with the external VIP? I thought this behaviour was by 'design' with ISA, where it used the primary IP of the external adpater through which the traffic leaves ISA.
To give an update on this, I eventually put this call to MS Support to help resolve and after almost 2 weeks of troubleshooting with them, got confirmation back that ISA's in an NLB array will 'Always' receive traffic on the NLB MAC irrespective of the Gateway Settings on the client machine. Therefore, traffic will always load-balance across each ISA server.
This is someting to do with Unicast Mode (vs Multicast Mode). So to force traffic through a particular ISA server, you need to set up NLB in Multicast Mode. Apparently if you want to configure Multicast Mode you need ISA 2006 SP1 installing (since the MS hotfix that previously supported this has now been withdrawn) and be pretty experienced in what your doing (counts me out then!).
Thanks for the update! I wasn't aware of that effect of unicast mode. I know that multicast mode is now supported, but haven't set it up yet. When you say that you have to be pretty experienced, are you saying that the multicast mode setup is a bear?
From: United Kingdom
Yeah, not hard, but a bit painful Tom.
It extends the ADAM schema, so you need to first decide which CSS is the schema master (Jim created a script for this on the ISA blog).
You then need to run some scripts to extend the schema and then use some switches to define the NLB mode you wish to use. Once the schema work has been done, you can then toggle backwards and forwards between the modes.
The confusing bit for me is that the scripts needed to enable the feature are not inlcuded with SP1 (that I could tell) but the actual ISA code that allows it to work is included.
I think an update to the GUI would have been a much nicer approach, but I guess time was limited...