Created attachment 1067919 [details]
server.log_exception

Description of problem:

User cannot create the GRE network under the Horizon with the maximum allowed Segmentation id (4294967295)


How reproducible:


Steps to Reproduce:
1. Open Horizon
2. Login as admin.
3. Go to the System->Networks page and click on Create Network
4. Under the Create Network form select: 
  - Name: any
  - Project: any
  - Provider Network Type: GRE
  - Segmentation ID: 4294967294

5. Submit Create Netwrok form by clicking on Create Network button. 

Actual results:
The error alert is displayed ("Error. Failed to create network")

Expected results:
GRE network should be created