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Chris_103447's avatar
Chris_103447
Icon for Altocumulus rankAltocumulus
Jun 23, 2015

Issues with Exchange 2013 load balancing through LTM (v11.6)

I have a support case open for this as well, but since no one has truly engaged in spite of a Sev1 classification, I'm hoping someone in the community can help. Thank you ahead of time.   We have ...
application delivery
exchange 2013
LTM
microsoft
Dayne_Miller_19's avatar
Dayne_Miller_19
Historic F5 Account
Jun 24, 2015

Hi Chris-

 

I'm sorry you're having issues with your Exchange deployment.

 

Off the top of my head, without looking at your case notes directly (which I'll do), it sounds to me like there's a strong possibility that you have a duplicate IP address on your "external" VLAN--meaning, your virtual server shares an IP address with something that already exists. That would explain a lot of things: the intermittent connectivity on the same L2 network, the ARP issues, the working connectivity from remote networks (because the intervening router already has a good ARP table entry, or hides the problem by trying repeatedly to get a good connection), etc. Can you move your Exchange virtual server(s) to an entirely new IP address on the same VLAN/subnet and let us know what happens?

 

On a separate note, we've made a conscious decision to keep SMTP as a separate entity/iApp for now, in part for reasons of not complicating the iApp any more, and in part because many/most of our customers use a 3rd-party SMTP relay or appliance on their DMZ to send and receive SMTP messages, and don't rely on Exchange itself for that. Yes, eventually there needs to be a Send and Receive connector somewhere in the Exchange environment, but BIG-IP doesn't necessarily sit in front of those connectors. In the future, we may incorporate SMTP directly into the Exchange CAS iApp, or allow the two iApps to be optionally "chained", but we haven't made a final decision on that yet.

 

  • Chris_103447's avatar
    Chris_103447
    Icon for Altocumulus rankAltocumulus
    Jun 25, 2015
    Dayne, thanks for your reply. I don't think that we're dealing with a duplicate IP address, since we see this on all of the virtual servers. I can verify that all of them were/are available and assigned only to the LTM virtual servers. Additionally, when I attempted the L4 pass-through test virtual server, it also was an unused IP and exhibited the same behavior. I'm fine with F5's decision to separate CAS from SMTP iApps, but there should be better documentation linking them as solutions. We use Cisco ESAs (IronPort) as our perimeter endpoint for SMTP, but mail gateways still have to deliver that mail back to Exchange over SMTP, so it has to be serviced somewhere.