node with dynamic IP

how can we manage the LTM to forward source natted traffic to the FQDN instead to the fixed IP?i think we can use RESOLV::lookup to resolve fqdn to ip address and then use node command to send traffic to.

 

 

RESOLV::lookup wiki

 

http://devcentral.f5.com/wiki/iRules.resolv__lookup.ashx

 

 

node wiki

 

http://devcentral.f5.com/wiki/iRules.node.ashx

 

 

by the way, just curious why it is not wildcard forwarding virtual.

e.g.

[root@ve1023:Active] config  b virtual bar list
virtual bar {
   snat automap
   destination 172.28.19.79:80
   ip protocol 6
   rules myrule
   profiles {
      http {}
      tcp {}
   }
}
[root@ve1023:Active] config  b rule myrule list
rule myrule {
   when HTTP_REQUEST {
        set dest [RESOLV::lookup @8.8.8.8 -a "www.google.com"]
        log local0. "\[RESOLV::lookup @8.8.8.8 -a \"www.google.com\"\]: $dest"
        log local0. "\[getfield $dest \" \" 1\]: [getfield $dest " " 1]"
        node [getfield $dest " " 1] 80
}

when HTTP_RESPONSE {
        log local0. "[IP::client_addr]:[TCP::client_port] -> [IP::remote_addr]:[TCP::remote_port]"
}
}

[root@ve1023:Active] config  curl -I http://172.28.19.79
HTTP/1.1 200 OK
Date: Thu, 22 Dec 2011 06:20:00 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
Server: gws
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
Transfer-Encoding: chunked

[root@ve1023:Active] config  
Dec 21 22:25:07 local/tmm info tmm[26866]: Rule myrule : [RESOLV::lookup @8.8.8.8 -a "www.google.com"]: 74.125.235.19 74.125.235.16 74.125.235.18 74.125.235.17 74.125.235.20
Dec 21 22:25:07 local/tmm info tmm[26866]: Rule myrule : [getfield 74.125.235.19 74.125.235.16 74.125.235.18 74.125.235.17 74.125.235.20 " " 1]: 74.125.235.19
Dec 21 22:25:07 local/tmm info tmm[26866]: Rule myrule : 172.28.19.80:58281 -> 74.125.235.19:80

Very cool usage of RESOLV::lookup. Tagging for 20LoL. ;)

 

 

Colin

Hey nitass,

 

 

Thanks a lot, works great, but I've got one more question :

 

 

from DNS reply I'm getting a set of IPs :

 

example :

 

xxx.xxx.xxx.xxx xxx.xxx.xxx.yyy

 

 

As both of them are set to $dest I'm getting :

 

TCL error: dynamic4-m - bad IP address format

 

 

==========

 

How can I get the first element parsed ?

You can use lindex to get the first list element:

 From: https://devcentral.f5.com/wiki/iRules.resolv__lookup.ashx

 Select the first returned IP address as the destination IP (inherits the destination port from the client's destination port).
when RULE_INIT {
   set static::dns_vs my_dns_vs
}
when CLIENT_ACCEPTED {

    Get IP(s) for hostname www.example.com against 4.2.2.1 name server
   set ips [RESOLV::lookup @$static::dns_vs -a "www.example.com"]

    Log result. If there are multiple IP's it could be a TCL list like {1.1.1.1 2.2.2.2 3.3.3.3}.
   log local0. "Looked up www.example.com and found $ips, parsed first element: [lindex $ips 0]"

    Check if the first list element was empty
   if {$ips eq ""}{
       Input wasn't an IP address, take some default action?
   } else {
       Select the IP 
      node [lindex $ips 0]
   }
}

Aaron