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Question 49

An LTM device has a virtual server configured as a Performance Layer 4 virtual listening on 0.0.0.0:0 to perform routing of packets to an upstream router. The client machine at IP address 192.168.0.4 is attempting to contact a host upstream of the LTM device on IP address 10.0.0.99.

The network flow is asymmetrical, and the following TCP capture displays:

# tcpdump -nnni 0.0 'host 192.168.0.4 and host 10.0.0.99'

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on 0.0, link-type EN10MB (Ethernet), capture size 96 bytes

05:07:55.499954 IP 192.168.0.4.35345 > 10.0.0.99.443: S 3205656213:3205656213(0) ack 3267995082 win 1480

05:07:55.499983 IP 10.0.0.99.443 > 192.168.0.4.35345: R 1:1(0) ack 1 win 0

05:07:56.499960 IP 192.168.0.4.35345 > 10.0.0.99.443: S 3205656213:3205656213(0) ack 3267995082 win 1480

05:07:56.499990 IP 10.0.0.99.443 > 192.168.0.4.35345: R 1:1(0) ack 1 win 0

4 packets captured

Which option within the fastL4 profile needs to be enabled by the LTM Specialist to prevent the LTM device from rejecting the flow?

    Correct Answer: B

    The Loose Initiation option within the fastL4 profile should be enabled to prevent the LTM device from rejecting the flow. This option allows the BIG-IP device to accept any TCP packet to start a connection, not just a SYN packet, which is essential in asymmetrical network scenarios where packets might not follow the traditional SYN, SYN-ACK, ACK sequence.

Discussion
GVKDOption: B

B - Correct. The Loose Initiation option allows the BIG-IP to initialize a connection when any TCP packet is received, rather than requiring a SYN packet for connection initiation. https://my.f5.com/manage/s/article/K8958