Manual Chapter : SNATs for server-initiated (outbound) connections

Applies To:

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BIG-IP AAM

  • 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP APM

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP Analytics

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP Link Controller

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP LTM

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP PEM

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP AFM

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP DNS

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0

BIG-IP ASM

  • 17.0.0, 16.1.3, 16.1.2, 16.1.1, 16.1.0, 16.0.1, 16.0.0, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0, 15.0.1, 15.0.0, 14.1.5, 14.1.4, 14.1.3, 14.1.2, 14.1.0
Manual Chapter

SNATs for server-initiated (outbound) connections

When an internal server initiates a connection to an external host, a SNAT can translate the private, source IP addresses of one or more servers within the outgoing connection to a single, publicly-routable address. The external destination host can then use this public address as a destination address when sending the response. In this way, the private class IP addresses of the internal nodes remain hidden from the external host.
More specifically, a SNAT for an outgoing connection works in the following way:
  1. Local Traffic Manager receives a packet from an original IP address (that is, an internal server with a private IP address) and checks to see if that source address is defined in a SNAT.
  2. If the original IP address is defined in a SNAT, Local Traffic Manager changes that source IP address to the translation address defined in the SNAT.
  3. Local Traffic Manager then sends the packet, with the SNAT translation address as the source address, to the destination host.
In this example of an outgoing SNAT, Local Traffic Manager causes three internal nodes, with the IP addresses
172.16.20.4
,
172.16.20.5
, and
172.16.20.6
, to advertise the public IP address
207.10.1.102
as the source IP address in the three outgoing connections.
Sample SNAT for multiple outgoing connections
Sample SNAT for multiple outgoing connections