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johnathan
Staff
Staff
October 1, 2024

Technical Tip: Adding more than 10172 addresses in a local-in policy does not work as expected

  • October 1, 2024
  • 0 replies
  • 394 views
Description

This article describes how to resolve a scenario where adding more than 10172 addresses in a local-in policy does not work and traffic is allowed/dropped.

Scope FortiOS 7.x.x+.
Solution

When adding a large number of addresses in a local-in policy, there is an implicit limit not visible to the user which can cause unexpected behavior.


When adding more than 10172 addresses, the IPs that are added after this limit will not be applied to the local-in policy.
This can cause some confusion when using a local-in policy to block traffic as IPs in that deny policy will be allowed.
Here is an example of a policy having this issue (many IP addresses configured in each group):


config1.PNG
It is possible to tell if hitting this limit by running 'diag firewall iprope list 100001' and there is ‘flag3 (40): truncated’ in the output.


iprope1.PNG

 

To resolve this, split the single local-in policy into multiple. Here is what the config looks like after doing this:

 

config2.PNG

 

While running the same command, there is no longer any 'flag3 (40): truncated’ and the number of IP addresses pushed to the policy is greater than 10172 (6051 + 1510 + 4399 = 11960)

 

iprope2.PNG