Exchange ActiveSync Connection error

Hi Folks,

We've got a client with an odd Exchange ActiveSync issue.

Here's the setup:

VMWARE ESXi host running two Windows Server 2012 R2 guests. One is a DC, the other runs Exchange 2013.

Their internet connection is dual-link of two ADSL lines (managed by a Cisco Meraki firewall) with static addresses to allow redundancy if there's an outage (which surprisingly hasn't occurred yet).

The staff all use their smartphones to access their office mailboxes using ActiveSync. On a regular basis, all of the phones have errors connecting to Exchange. The only fix is to remove and re-add the account.
This is cross-platform on Android and IOS.

Is there some kind of ActiveSync timeout, or the like in Exchange 2013?

Any help/advice would be appreciated, thanks.
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MikeIT ManagerCommented:
Some more info would be helpful, like what the error actually is.

Also, are they connected to the corporate wifi when this happens?
Jakob DigranesSenior ConsultantCommented:
As Shadowless127 says, we'd probably need some more information:

- does this happen in office, outside of office or both?
- When connected to LAN, are they connecting to internal or external DNS
- Does this happen to several device types, both iOs and Androids??
- Looking at application event viewer in Exchange 2003 - do you see any errors relating to active sync?
- Is mobile sync published trough some reverse proxy, or directly to Exchange 2013
- Do clients authenticate using certificates, by any chance?
- Do all clients loose access simultaniously, or after the same amount of time - or just random?
- test here please;

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Me, I will think there is something not performed on the Cisco appliance.

If failover is not enabled the device might be working on Load Balance, nothing wrong there unless there are no binding rules to control the flow, the appliance might receive request on one IP but sending out the info onto another to balance the load on it.

Make sure the appliance is really on failover mode.
tech_tonicAuthor Commented:
These were all excellent questions to ask and provided good avenues to help diagnose. Sadly we couldn't complete diagnosis and resolve the issue due to the client moving to another provider.
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