301B: BIG-IP LTM Specialist: Maintain and TroubleshootDemo

Question

An LTM device has a virtual server configured as a Performance Layer 4 virtual server, listening on 0.0.0.0:0, to route 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 at IP address 10.0.0.99.

The network flow is asymmetric, and the following TCP capture is displayed:

# 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 &gt; 10.0.0.99.443: S 3205656213:3205656213(0) ack 3267995082 win 1480  
05:07:55.499983 IP 10.0.0.99.443 &gt; 192.168.0.4.35345: R 1:1(0) ack 1 win 0  
05:07:56.499960 IP 192.168.0.4.35345 &gt; 10.0.0.99.443: S 3205656213:3205656213(0) ack 3267995082 win 1480  
05:07:56.499990 IP 10.0.0.99.443 &gt; 192.168.0.4.35345: R 1:1(0) ack 1 win 0  
4 packets captured

Which option in the fastL4 profile must the LTM Specialist enable to stop the LTM device from rejecting the flow?

A Loose Close
B Loose Initiation
C Reset on Timeout
D Generate Initial Sequence Number

Explanation

FastL4 Loose Initiation allows the LTM to initialize a connection when it receives any TCP packet instead of requiring a SYN that begins a locally known handshake. This supports asymmetric or mid-flow traffic that otherwise has no matching connection-table entry and can be reset. F5 documents this behavior for the loose-initialization FastL4 setting.

Learn more

F5 BIG-IP tmsh Reference: ltm profile fastl4

301B: BIG-IP LTM Specialist: Maintain and TroubleshootDemo

AstroTutor

Notes

Readiness

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