Media is only working when NAT is enabled on F5 (Want to disable sNAT as per microsoft advise)

Hi,

 

Working on configuring lync 2013 edge servers using F5 as a HLB. All service are working fine including Media.

 

Let me try to explain the ENV

 

1> 2 Edge server (Behind the F5 LB)

 

2> Each server have public IP address for external (SIP, WebConf & AV)

 

3> Internet records for all three service are pointing to F5 VIP

 

3> NAT is enabled for SIP & Webconf, NAT is disabled for AV (in F5)

 

Problem :

 

AV service only start working fine when we enable NAT on F5 and start getting failed if we turn it OFF. As per Microsoft TechNet article the best praticse is to disable sNAT for AV

 

Please advise if you have configured your EDGE server wit F5 and disabled sNAT, how its working for you . What we should change in F5 to make it work ??