10. Does using a NAT (or NAPT) device cause problems with Nexus?

In short, yes it can. There is a default limit to the number of connections per minute that are accepted from a single IP address. This can be caused by the sheer numbers of users behind a Network Address (and Port) Translation device and/or by some users having a large number of connections being opened rapidly. Users may find the interface via Outlook or Outlook Web App to be very slow or intermittently problematic. They may also see "This webpage is not available" when trying to log in to OWA or SharePoint.

Note that the limit applies to usage of both Exchange and SharePoint. It is often the multiple connections that can often occur per user when interacting with Exchange that can cause the limit to be exceeded. However, once exceeded, it can affect SharePoint users as well as Exchange users.

If you wish to use a NAT/NAPT device in front of users who are likely to access Nexus (Exchange and SharePoint), please register this device with the Nexus Team. Send the IP address(es) to help@it.ox.ac.uk prefixing the subject line [ITSS] with a short explanation. Once the exception is created at the Nexus Threat Management Gateway your users' performance issues should be resolved.

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