Unable to attach an instance to a network

Hello dears,

I'm trying to attach an instance to an network using Horizon and OpenStack API but got the following error (Horizon is less specific for the reason of the error) :

$ nova interface-attach --net-id --fixed-ip
ERROR (ClientException): Unexpected API Error. Please report this at http://bugs.launchpad.net/nova/ and attach the Nova API log if possible.
(HTTP 500) (Request-ID: req-03575d3a-84a9-4c91-9a5b-6c903c604a7c)

The error class says `PortLimitExceeded_Remote` and, indeed, when I detach an existing port and retry my command, it works.

My questions are:

* What is the limit of number of port per public cloud project?
* Is it possible to increase this limit?

Thank you in advance for your prompt reply.

Warm regards

Younes