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AhmedSaied_2402's avatar
AhmedSaied_2402
Icon for Altostratus rankAltostratus
Jan 20, 2019

BIG IP DNS MX

Hello,

 

In intelligent DNS resolution we can use wide IPs and iRules

 

example to resolve type A when can use wide IP type A and iRule as below

 

when DNS_request { host 10.10.10.10 }

 

but how can do the same for wide IP with MX type what will be its iRule ?!

 

application delivery
BIG-IP
BIG-IP DNS
dns
irule
mx
  • Kai_Wilke's avatar
    Kai_Wilke
    Icon for MVP rankMVP
    Jan 21, 2019

    Hi Ahmed,

    a DNS response to an MX query contain just a FQDN value, so you don't need to care about wide IPs.

    Check the iRule sample below to get an overview how MX DNS responses can be crafted... 

    when DNS_REQUEST {

    if { ( [string tolower [DNS::question type]] eq "mx")
     and ( [string tolower [DNS::question name]] eq "domain.de" ) } then {

         Defining DNS answers for the requested MX records (Question Name = Domain Name, ttl = 600, class = IN, type = MX, data = priority FQDN) 

        DNS::answer insert [DNS::rr "domain.de 600 IN MX 100 mx1.domain.de"] 
        DNS::answer insert [DNS::rr "domain.de 600 IN MX  50 mx2.domain.de"] 

         Changing "Authorative Answer" DNS header to true.

        DNS::header aa 1 

         Sending the DNS response

        DNS::return 
    }

}

    Note: After the DNS response has been received by the MTA, it will perform an additional A and/or AAAA record lookups for the received FQDNs. This is where the wide IP comes into play...

    Cheers, Kai