Symptoms

The TRUNK name in an F5 ethernet trailer is limited to 15 characters in tcpdump captures.

Impact

TRUNK name in the F5 ethernet trailer is truncated to 15 characters in the tcpdump capture. The tcpdump utility adds internal tmm information to tcpdump captures. This is used for diagnostic purposes and is not used for communication between client and server. That said, if you have multiple trunks where the first 15 characters are the same, there is no way to distinguish between the traffic information for the various trunks in the tcpdump output. Note: The tmm process correctly handles the longer names in other circumstances (e.g., adding/removing trunks, or looking up a trunk by name).

Conditions

-- Trunk name is longer than 15 characters. -- Send traffic from client to server. -- Capture traffic on the BIG-IP system using tcpdump.

Workaround

Although there is no workaround for the issue of the trunk name being truncated, if you have multiple trunks in which the first 15 characters are the same, you should rename them so they are distinguishable in the case where you might need to collect tcpdump data. You can read more about the information tcpdump gathers here: K13637: Capturing internal TMM information with tcpdump :: https://support.f5.com/csp/article/K13637.

Fix Information

None

Behavior Change