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Tyler_Lund_1130's avatar
Tyler_Lund_1130
Icon for Nimbostratus rankNimbostratus
Jan 18, 2006

Selective Source NATing

Hello,

I have one BigIP system running 9.1 on which I've deployed the following iRule to turn on source NATing based on a particular source address:

when LB_SELECTED {
  if { [IP::addr [IP::remote_addr] equals ""] } {
    snat  (or automap)
  } else {                      
    snat none                   
  }                             
}

This works great. I need to duplicate this functionality in 4.5. 4.5 doesn't appear to have a snat command, but a hidden version of snatpool seems to exist. I was thinking of something like:


snatpool internal_snat_pool {
  member 1.2.3.4
}
if (client_addr ==  netmask  {
   use snatpool internal_snat_pool
}
use pool

Does this sound reasonable? The only bummer is that It appears I'd have to have one of these rules for every virtual server, where as in 9.x I can reuse the same rule over and over.
application delivery
dev
devops
iRules
v4

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  • Colin_Walker_12's avatar
    Colin_Walker_12
    Historic F5 Account
    Jan 20, 2006
    It looks like you're on the right track. That should work the way you're looking for it to, provided you get the right information in there for the variables.

     

     

    -Colin
  • Tyler_Lund_1130's avatar
    Tyler_Lund_1130
    Icon for Nimbostratus rankNimbostratus
    Jan 25, 2006
    Thanks.

    Ran into my first snag... I tried using the internal address of the load balancer (the gateway for the pool hosts) as the snat pool address, but got the following error when loading:

    ./bigip.conf: "The snatpool contains an invalid member."

    Under 9.x, I'm able to use the gateway IPA in a source NAT. For 4.5 should I be using a different IPA, or is my syntax for defining the snatpool incorrect? I realize this feature is unsupported in 4.x, but I'm hoping someone has done this before and can offer some hints.

    This is the exact configuration used:

    snatpool internal_snat_pool {
  member 216.27.85.193
}
rule SNAT_Internal_Test {
   if (client_addr == 216.27.85.192 netmask 255.255.255.224) {
      use snatpool internal_snat_pool                         
   }
   use pool Test-Pool
}
  • Martin_Machacek's avatar
    Martin_Machacek
    Historic F5 Account
    Jan 26, 2006
    Tyler,

     

     

    your syntax is correct. 4.5 just does not allow to use *any* self-IP as a SNAT pool member.