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SNAT and VIP for use with SIP


We have 2 SBC's on our internal network that we are wanting to SNAT out over a specific IP to our TelCo. I have created a SNAT with the address pool of the two devices and outbound seems to be working fine. The issue comes with the inbound. I have created a VIP with the same IP and put the 2 SBC's in a Pool behind it. The issue is that it looks like no traffic is coming back into the VIP, but somehow all traffic is being sent back to just one of the SBCs.

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Comment made 28-Feb-2017 by Chase Abbott

If the traffic from the SIP source is heading back to the SBC, is the SBC using the BIG-IP as it's outbound gateway? There may be an issue with SIP TLS if it's trying to async route out a different route.... but that's with my way back hat on.

Comment made 28-Feb-2017 by mike.drennen 268

The SBC is using the BIG-IP as it's gateway. It seems logically that traffic out of the SBC passes through the Big-IP, then is SNAT'd. (which does happen). On the return to the Big-IP, we have a VIP with the same ip to take the traffic and load balance it. However, traffic just goes back to one SBC (whichever responded initially, and it sticks to that one) and you never see anythig passing through the VIP.

Comment made 01-Mar-2017 by Leonardo Souza 3174

Can you provide part of your configuration, mainly the virtual server and SNAT or SNAT pool? If the initial traffic pass via F5, the return traffic should be processed by the same virtual server in the way back automatically (so, only one virtual server). If you require the traffic to start in the other direction, you need another virtual server for that.


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