Bug ID 470715: Excessive IP fragmentation on tmm_bp vlan causes ftp data loss with vlan name >= 16 characters long

Last Modified: Feb 13, 2019

Bug Tracker

Affected Product:  See more info
BIG-IP All(all modules)

Known Affected Versions:
10.2.1, 10.2.2, 10.2.3, 10.2.4, 11.0.0, 11.1.0, 11.2.0, 11.2.1, 11.3.0, 11.4.0, 11.4.1, 11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8

Fixed In:
12.0.0, 11.6.1, 11.5.1 HF5, 11.2.1 HF15

Opened: Jul 08, 2014
Severity: 2-Critical
Related AskF5 Article:
K16019

Symptoms

When a vlan name is >= 16 characters including the /Common/ folder name prefix, the internal packet size will exceed the configured MTU size of 1582 on the MPI channel. This causes excessive IP fragmentation on tmm_bp vlan and high cpu usage. In some cases it can also cause packet loss.

Impact

This can cause excessive IP fragmentation on tmm_bp vlan and high cpu usage. In some cases it would also cause packet loss.

Conditions

Vlan names (16 characters or longer) are being used. This length also counts the name of the partition.

Workaround

Use shorter vlan names.

Fix Information

A new db variable vlan.backplane.mtu has been added to configure tmm_bp vlan mtu size, and the new default backplane MTU is set to to 1640.

Behavior Change

A new db variable vlan.backplane.mtu has been added to configure tmm_bp vlan mtu size, and the new default backplane MTU is set to to 1640.