Forum Discussion

omar_padilla's avatar
omar_padilla
Icon for Altocumulus rankAltocumulus
Mar 09, 2018

Allow some DNS queries and block the rest

Hello,

 

I want and irule to just allow some DNS queries and block the rest.

 

I was trying with this that blocks some dns request and permit the rest

 

when DNS_REQUEST { switch -glob [string tolower [DNS::question name]] { "*.google.com" - "google.com" { DNS::header rcode NXDOMAIN DNS::return } } }

 

But I can not negate it and make it works in the other way.

 

Any idea how I could do this?

 

Thanks in advanced

 

BIG-IP DNS
devops
dns
dns queries
irule
iRules
security
  • Surgeon's avatar
    Surgeon
    Ret. Employee
    Mar 10, 2018

    what do you mean by saying "make it works in the other way"?

     

  • Stanislas_Piro2's avatar
    Stanislas_Piro2
    Icon for Cumulonimbus rankCumulonimbus
    Mar 10, 2018

    In switch command, do nothing in conditions you want to allow and block in default condition

    when DNS_REQUEST {
    switch -glob [string tolower [DNS::question name]]  {         
        "*.google.com" -        
        "google.com" {        
              do nothing       
        }        
        default {        
            DNS::header rcode NXDOMAIN             
            DNS::return             
        }            
    } 
}