101 · Question #90
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 E. 10.10.1.33. When a SNAT pool is configured on a BIG-IP virtual server, the BIG-IP selects the SNAT pool member that resides in the same network as the chosen pool member to ensure server return traffic routes correctly back through the BIG-IP.
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
- A150.10.30.30
- B150.10.33.33
- C10.10.1.10
- DIt could be any of the addresses of the members of the loadbalancing pool.
- E10.10.1.33
- F200.10.10.10
How the community answered
(42 responses)- A5% (2)
- C10% (4)
- E83% (35)
- F2% (1)
Why each option
When a SNAT pool is configured on a BIG-IP virtual server, the BIG-IP selects the SNAT pool member that resides in the same network as the chosen pool member to ensure server return traffic routes correctly back through the BIG-IP.
150.10.30.30 is the virtual server IP address, not a valid SNAT translation address.
150.10.33.33 is a SNAT pool member but resides in the external 150.10.x.x network, not in the same network as the pool members (10.10.1.x), so it would not be selected for server-side SNAT.
10.10.1.10 is a BIG-IP self IP address, not a member of the configured SNAT pool.
SNAT translates the source to a configured SNAT pool address, not to a load balancing pool member address.
The load balancing pool members are in the 10.10.1.x network. The BIG-IP chooses the SNAT pool member 10.10.1.33 because it is on the same subnet as the server-side pool members, ensuring the servers route their return traffic back through the BIG-IP rather than directly to the client. This is the standard SNAT pool member selection behavior on F5 BIG-IP.
200.10.10.10 is the original client source IP; because SNAT is configured, the source IP is replaced and never reaches the pool member.
Concept tested: SNAT pool member selection based on server network
Source: https://techdocs.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-concepts-11-4-0/ltm_snat.html
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