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Category: F5 Networks

“SSL Handshake failed for TCP” in LTM log on F5

Any F5 BIG-IP connected to the internet will be generating this log message a ton in /var/log/ltm:

01260013:4: SSL Handshake failed for TCP x.x.x.x:x -> y.y.y.y:443

This is simply an informational message indicating the peer closed the connection before completing the handshake. As this provides little to no information, you can often safely filter this from the LTM log by creating a log filter.

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Taking a useful packet capture using tcpdump

When troubleshooting an issue on any device where network connectivity is impacted, a packet capture is still king. This is not to say every 403 Forbidden error needs to be examined in Wireshark, but when a user reports their browsing saying the connection was reset or a timeout was hit, it might be time to fire up tcpdump.

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