101 · Question #81
A BIG-IP has the following objects configured: - A SNAT pool with 2 members: 150.10.33.33 and 10.10.1.33 - A loadbalancing pool with 5 members: 10.10.1.110.10.1.5:80 - The BIG-IP has two self-IP addre
The correct answer is B. 10.10.1.33. When a SNAT pool is configured on a BIG-IP, the system selects the SNAT pool member that resides on the same network as the chosen load balancing pool member for the server-side connection.
Question
A BIG-IP has the following objects configured:
- A SNAT pool with 2 members: 150.10.33.33 and 10.10.1.33
- A loadbalancing pool with 5 members: 10.10.1.110.10.1.5:80
- The BIG-IP has two self-IP addresses: 150.10.10.10 and 10.10.1.10
A virtual server at 150.10.30.30:80 that is associated with both the SNAT pool and the loadbalancing pool. If a client at IP address 200.10.10.10 initiates a connection to the virtual server, what will the source IP address be in the packets sent to the chosen pool member?
Options
- A150.10.33.33
- B10.10.1.33
- C10.10.1.10
- D150.10.30.30
- E200.10.10.10
- FIt could be any of the addresses of the members of the loadbalancing pool.
How the community answered
(17 responses)- B71% (12)
- D6% (1)
- E12% (2)
- F12% (2)
Why each option
When a SNAT pool is configured on a BIG-IP, the system selects the SNAT pool member that resides on the same network as the chosen load balancing pool member for the server-side connection.
150.10.33.33 is on the external network (150.x.x.x) and is not on the same subnet as the pool members (10.10.1.x), so BIG-IP would not select it for server-side connections to those pool members.
10.10.1.33 is the only SNAT pool member on the same subnet (10.10.1.x) as the load balancing pool members; BIG-IP selects this address as the source IP for server-side packets to ensure proper routing back through the correct VLAN and internal self-IP.
10.10.1.10 is the BIG-IP self-IP on the internal VLAN, not a SNAT pool member; a configured SNAT pool overrides default behavior and uses a SNAT pool member address as the source, not the self-IP.
150.10.30.30 is the virtual server's destination IP as seen by the client, not the source address used in server-side packets sent to pool members.
200.10.10.10 is the original client IP; the SNAT pool is specifically configured to replace this address on server-side connections so pool members never see the original client source.
The source IP is governed by the SNAT pool configuration, not the load balancing pool; load balancing pool member addresses are server destinations, not candidate source addresses.
Concept tested: SNAT pool member selection based on server-side subnet
Source: https://techdocs.f5.com/en-us/bigip-15-1-0/big-ip-local-traffic-manager-concepts/address-translation.html
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