FQDN Node with Route Domains

Currently this is not supported with FQDN nodes, though it might happen if FQDN nodes are created in an administrative partition with a nonzero route domain (I have not tested this).

There is an RFE open for this, tracked as

ID522465

Here's my attempt at it...

 Rule Name:        MY_RD_FQDN_IRULE
 Rule Date:        01/07/2016
 Rule Version:     1.0

 Rule Description: This iRule is designed to lookup an IP for an FQDN and then use the IP for the serverside connection.
                   Simply edit the RULE_INIT variables to modify for your needs.  
                   Test before using in any environment. This rule is provided *as-is* without warranty or liability. 
   
 Rule History:     1.0 - 01/07/2016 - C.Spathas (Ardenta) - Initial Version inspired by DevCentral
                   https://devcentral.f5.com/questions/dynamic-pool-members-with-dns-resolution

when RULE_INIT {

     Set some static variables and lists
    set static::MY_RD_FQDN_GBLVAR "www.google.com"
    set static::MY_RD_FQDN_ROUTE_DOMAIN_GBLVAR "%1"
    set static::MY_RD_FQDN_DNS_SRV_GBLST {8.8.8.8 8.8.4.4}

     Set debug logging on/off (0 for none, 1 for drop/deny/error and 2 for all logging)
    set static::MY_RD_FQDN_DEBUG_GBLVAR 2

}

when CLIENT_ACCEPTED {

     Select a DNS server from the list and sppend the Route Domain
    set DNS_SERVER_LCLVAR "[lindex $static::MY_RD_FQDN_DNS_SRV_GBLST [expr {int(rand()*[llength $static::MY_RD_FQDN_DNS_SRV_GBLST])}]]$static::MY_RD_FQDN_ROUTE_DOMAIN_GBLVAR"

     Debug Logging
    if {$static::MY_RD_FQDN_DEBUG_GBLVAR==2}{log local0. "DNS Server selected was $DNS_SERVER_LCLVAR"}

     Perform the Lookup and append the Route Domain
    set FQDN_IP_LCLVAR "[lindex [RESOLV::lookup @$DNS_SERVER_LCLVAR -a $static::MY_RD_FQDN_GBLVAR] 0]$static::MY_RD_FQDN_ROUTE_DOMAIN_GBLVAR"

     Debug Logging
    if {$static::MY_RD_FQDN_DEBUG_GBLVAR==2}{log local0. "The resolved IP for FQDN $static::MY_RD_FQDN_GBLVAR is $FQDN_IP_LCLVAR"}

     Perform some rudimentary error checking
    if { $FQDN_IP_LCLVAR ne "" } {

         Use the FQDN IP as the node if there is one
        node $FQDN_IP_LCLVAR

         Debug Logging 
        if {$static::MY_RD_FQDN_DEBUG_GBLVAR==2}{log local0. "The connection for [IP::client_addr]:[TCP::client_port] was sent to $FQDN_IP_LCLVAR"}

    } else {

         If there is no FQDN IP then drop the connection
        drop

         Debug Logging         
        if {$static::MY_RD_FQDN_DEBUG_GBLVAR>0}{log local0. "No IP was resolved."}
    }

}

Having had to deal with this recently, I've added a Code Snippet that addresses this issue but also adds redundancy to the DNS queries, validation of answers and caching.

https://community.f5.com/t5/codeshare/dynamic-fqdn-node-dns-resolution-based-on-uri-with-route-domains/ta-p/289099

On v14.1.2 I tested creating an fqdn node in an administrative partition with a nonzero route domain and it gets created in Common aka route domain.

It's still not officially supported.

https://support.f5.com/csp/article/K29925900

I made a post earlier this year about the same subject but never found a solution.

Only received a request for enhancement number:

522465 RFE: Route domain support for FQDN nodes

https://devcentral.f5.com/s/question/0D71T0000069veZ/irule-for-combination-of-fqdn-pool-member-and-route-domains?s1oid=00D00000000hXqv&s1nid=0DB1T0000008Ony&emkind=chatterCommentNotification&s1uid=0051T000008eeBk&emtm=1581302191188&fromEmail=1&s1ext=0

https://devcentral.f5.com/s/question/0D51T00007HPxq7SAD/ltm-fqdn-based-node-addition-with-route-domain