# Enforce Valid DNIS Length

 In this article, I am going to show you how to block calls that have valid length for the DNIS and ANI. 

Here is how a normal basic routing plan looks.  It basically just route all calls according to the vendor trunks defined in the dynamic route specified. 

![](https://2160858555-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MYRPW5mw1EmjxhpuA4p%2F-MYWPCrfhziESThfOiBU%2F-MYWQGuAq1LlTXsDwWyR%2Fimage.png?alt=media\&token=730a348e-7837-4ae4-829d-cb4a52b34f70)

However, you can set it so that this rule is applied with the length of ANI and DNIS meets the valid size. 

You can do this by clicking "Edit" on this rule:

![](https://2160858555-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MYRPW5mw1EmjxhpuA4p%2F-MYWPCrfhziESThfOiBU%2F-MYWQXnHgn7ucZ0bbu_G%2Fimage.png?alt=media\&token=a6b03be3-f196-4aa4-ba59-38b52061ea6a)

You can use ANI/DNIS Prefix, Min Length, and Max Length to specify traffic you don't like.  For those traffic, you can send them to a different Dynamic or Static Route that either always return 503 or route to a miss call vendors like some of our clients are doing.