Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

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Bubbagump_12531's avatar
Bubbagump_12531
Icon for Nimbostratus rankNimbostratus
Nov 29, 2015

SSLDump issues: ERROR: Length mismatch

I am trying to debug some SSL handshake errors and it seems ssldump is different enough on the LTMs to make me a bit nuts. After a few seconds it dies with: ERROR: Length mismatch. The entire interwebs say this is because it needs a '-s 0' command line switch which the F5 version of ssldump doesn't have. Any ideas how to capture more than a few seconds of traffic?

 

3 Replies

  • Bubbagump_12531's avatar
    Bubbagump_12531
    Icon for Nimbostratus rankNimbostratus
    Nov 30, 2015

    That is what I was afraid would be the solution as I was trying to avoid the tcpdump then feed into ssldump method. Ah well, seems that is the only option. Thanks!

     

  • canttalkeating's avatar
    canttalkeating
    Icon for Altocumulus rankAltocumulus
    Dec 16, 2019

    Hi Bubbagump 12531,

     

    I'm probably about 4 years late to this party but if you're just tshooting an SSL negotiation issue then running #ssldump -i vlan_100_internal host 10.0.100.41 would give you a continuous feed of SSL negotiation activity to the console for analysis

     

    If wanting to examine within Wireshark then the -s0 flag would be required to allow the ssldump to be ran against the packet capture as it requires the whole packet to be available