Forum Discussion

Tski81's avatar
Tski81
Icon for Nimbostratus rankNimbostratus
Apr 10, 2020

BIG-IP SRV record response

Hello, was looking for some help on this. I am wanting to create an iRule that responds with individually weighted FQDN's when a specific SRV record is requested. Since I am attaching to a SRV WIP, was wondering how this code actually shapes up. Thanks all!!

 

I am doing this on big IP and keep getting undefined procedures 


when DNS_REQUEST { 

    if { [DNS::question type] equals "SRV" } then {
 
       SRV response
      DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 10 50 8443 server1.domain.com"
      DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 10 50 8443 server2.domain.com"
      DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 20 50 8443 server3.domain.com"
      DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 20 50 8443 server4.domain.com"
       
      DNS::return
 

  }
}
BIG-IP
devops
iRules
  • Pedro_Haoa's avatar
    Pedro_Haoa
    Ret. Employee
    Apr 13, 2020

    Hi,

    Maybe you can try the following example:

    when DNS_REQUEST {
    if { [string tolower [DNS::question name]] starts_with "_service._tcp.dc._msdcs.domain.com" } then {
        if { [DNS::question type] equals "SRV" } then {
            # Set your TTL
            set ttl 300
            # Log query details
            log local0. "\[DNS::question name\]: [DNS::question name], \[DNS::question class\]: [DNS::question class], \[DNS::question type\]: [DNS::question type]"
            # Generate an answer with SOA information
            DNS::authority insert "domain.com. $ttl IN SOA server1.domain.com hostmaster.domain.com 1337 900 600 86400 3600"
 
            # Generate an answer with four SRV records
            DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 10 50 8443 server1.domain.com"
            DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 10 50 8443 server2.domain.com"
            DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 20 50 8443 server3.domain.com"
            DNS::answer insert "[DNS::question name]. $ttl IN [DNS::question type] 20 50 8443 server4.domain.com" 
            
            # Generate additional records
            DNS::additional insert "server1.domain.com. $ttl IN A 192.168.1.1"
            DNS::additional insert "server2.domain.com. $ttl IN A 192.168.1.2"
            DNS::additional insert "server3.domain.com. $ttl IN A 192.168.1.3"
            DNS::additional insert "server4.domain.com. $ttl IN A 192.168.1.4"
            
            # Stop further processing of the query after this iRule and send the answer to the client
            DNS::return
        }
    }
}

    I hope it helps.